Introduction to computer

We are living in an information age dependent upon digital information. Digital information is electronic information, the result of computer processing. Every type of job relies upon getting information, using it, managing it, and relaying information to others. Computers enable the efficient processing and storage of information.

Do not think of a computer merely as the machine with the keyboard and the mouse, although that might be true for some types of computers. Embedded computers may be inside your household appliances, the VCR, the automobile, planes, trains, powerplants, water purification plants, calculators, and even inside a few toys. These embedded computers are very small. They affect our lives each day. Why, even modern traffic lights operate with computers. They are all around us. Think of additional ways in which computers affect our lives each day.



The Four Operations of a Computer System
Input
Home computers are microcomputers. Input is supplied to the microcomputer with the use of a keyboard, a mouse, or another input device. These input devices may be called peripheral devices.
Processing
Processing is done inside the computer in an area called the central processing unit (CPU). Processing is the conversion of input to output.
Storage
Storage refers to holding information somewhere.
RAM, Random Access Memory, is short-term memory. It is volatile memory because the memory is automatically "erased" when the power is turned off or interrupted. The RAM memory is located inside the computer case on the motherboard. A motherboard is not the keyboard. The keyboard is what you type with. A motherboard holds RAM memory, electronic circuits and other computer parts including the central processing unit. ROM, Read-Only-Memory, is not volatile meaning the memory is still there when power is interrupted or turned off. When the computer is turned back on again, ROM memory is still in storage on the internal hard disk.
Output
Output is the result of a computer process. Output may be viewed on a monitor screen, heard through speakers, printed on printers, and so forth. Output devices may be considered hardware and are also considered to be peripheral devices.





A Basic Computer "System"
A computer system refers to the computer AND all of its equipment. Equipment like speakers, printer, keyboard, scanner, etc. is called peripheral equipment, sometimes shortened to "peripherals". The central processing unit (CPU) is considered to be "the computer". Without peripheral equipment (such as monitor, printer, speakers, etc.) for input and output the microcomputer (home computer) will not be able to do anything you find useful.

Your computer system cannot help you type a letter unless you have some type of software (program) to do this. Most typing is handled by a "word processing" program. A software program for your computer can be purchased at stores like Office Depot, Staples, and computer stores. Check your local telephone directory for a computer store in your area. Sometimes when you purchase a computer it already has a word processing program installed. If you buy a computer from a large electronics chain store, even if you have to travel out of town, you will get a better price as a rule than buying from a smaller chain store in town. Ask in town first, if they would be willing to match another store's Advertised price... See "Buying A Computer", next.





Buying A Computer
It is best to ask and to compare features before you buy a computer. The first question to ask yourself is, "What do I want a computer to do?" Do you need it only for e-mail and a little light letter writing or do you need it for graphics and Web page authoring? Will you also want extra storage for your music files or graphics files? Do you need any hardware for game playing? What type of Internet connection will you have: dialup, cable, DSL, or other broadband connection? Will you be needing a computer for school work? Accounting? Make a list of what you need the computer to do before you talk to anyone about purchasing a computer. Your needs will be different that those of the next person. Visit Computer Company Web sites.





The PC vs. The Macintosh
There are several computer systems available for home computing but the two most common types of computers are the PC (personal computer), manufactured by companies such as DELL, IBM, NEC, GATEWAY, HP, SAMSUNG, and others -- and the Macintosh manufactured by Apple Computer.
The Macintosh Computer
The Macintosh computer is commonly referred to as a "Mac". Apple Computer has produced a PowerMac, an iMac, and a PowerMac G4, and the PowerMacG5. The operating system of the PowerMac G4 or G5 has undergone revisions. Each major version also has a name: OS X version 10.2.x is Jaguar; version 10.3.x is Panther, and the version 10.4.x is Tiger. The Apple PowerMac computers(the G4 and the G5) have two processors (for parallel processing) instead of just one, and there is space inside the computer to upgrade to 4 hard disks in a RAID array to give more power to the computers functioning as a server. Sometimes the computer tower is called a "box" which is a slang word for "the computer". You could say, "there are two processors inside the box."

There is software specially designed for the PowerMac computers to help move files from a Windows 98, ME, or 2000 system (XP is not listed on the box) to the Mac OS X. This software is called Move2Mac and is a product of Detto Technologies. I found my copy of the shrink-wrapped software on a shelf at a large Fry's Electronics store. A lot of computer software can be purchased using a credit card with a secure connection over the Web, then downloading that software to your own computer. I prefer having a CD or other disk with the software on the disk.

Downloading via FTP is the process of moving files from another computer over a network connection to a local computer (like your own home computer) using File Transfer Protocol (FTP). If working at school or on the job you have to get permission to download files, for security reasons. You can download files using a Mac or a PC computer. Both use File Transfer Protocol.

The Macintosh has excelled in the commercial graphics and publishing industries and thousands of people prefer a Mac for home use rather than a PC. The PC computers currently have a much greater market share and there are millions in use in homes and businesses throughout the world. When you attend college the college will specify which type of computer, Mac or PC, will be in use at the college for faculty and students. Some colleges use just Mac computers in campus buildings and for the faculty. Other colleges use PCs.

Each PC running a specific operating system such as Windows 2000 is able to use any software that says WIN95/98/NT/2000 on the box. The Windows2000 operating system can also run any software specified for WIN95/98/NT/2000 as well as any software specified as Windows 9.x/NT/2000. If in doubt about buying the correct software for your system, the store clerks will be happy to assist you if asked. If you are using Windows XP, make sure that the software you buy has Windows XP included in the "System Requirements", usually found on the side panel of the box for shrink-wrapped software (boxed software).

(In the following paragraphs I use OS to mean "operating system")
Prior to the Macintosh OS X operating system the Macs used an operating system based upon a single processor (computer CPU) which processed data and ran applications using what was called cooperative multitasking. Cooperative multitasking allowed programs to sometimes take control of the central processing unit. Now with the newer Macintosh operating system, OS 10.2.x (Jaguar) and later versions there is a UNIX-like kernel in the operating system, two processors and the central processing unit processes data with symmetric multiprocessing (uses both CPU's or "chips" to process data) and it uses preemptive multitasking, not allowing any application to take control of the central processing units.

If users want to run older software, the PowerMac G4 is a dual-booting machine meaning you can either boot into the older OS 9.2 or a version of OS X. (This is called "dual bootable".) Software written for the OS X (pronounced OS ten) will not run in the OS 9 environment but older legacy software is capable of being run while booted into the newer OS X, just that the newer features of the OS X will not be available when running applications designed for the OS 9 or older operating systems. The Mac G5's and newer versions of Os X have more multimedia features than the earlier G4's with the older versions of OS X. Get to the Apple Computer Web site for what's new now. The computer industry is not standing still... changes are rapid and one article online cannot capture what is now current.



Central Processing Unit and Software Compatibility
The computer processor inside a PC or PC-clone computer has totally different architecture (microscopic "wiring" schematic) inside the central processing unit chip (the CPU, or "chip"). In other words, the specific way the circuits are laid out in a computer chip (CPU, central processing unit) is called the chip architecture. PC chips and Mac chips have processing units with totally different architecture. Software is not interchangeable. Buy Mac software for the Macintosh and buy PC software for PC computers. An Apple or Mac computer is not a PC. Most PC Computers are sold new with a Windows operating system but keep in mind that other operating systems can also run on PC-architecture machines. One example of another operating system that can run on a PC machine is Linux for Windows. When two operating systems are on a disk they are installed on separate "partitions" of the disk. That is similar to two songs on one CD having to be on separate "tracks".



Hardware and Software
Usually, things you can see and touch on a computer or inside a computer are called "hardware" whereas programs for the computer (digital instructions) are called software. Software is created by a computer programmer who writes lines of code for the computer. An interpreter or compiler is a smaller program which changes the programmer's code into machine instructions for the central processing unit. After much testing and debugging, the programmer's code is finally "packaged" into executable files which make up the final "software" which can be purchased later, or might be "bundled" with the computer when you buy it (meaning that some software is already installed when you buy the computer.)

MizzNina feat. Colby O'Donis "What You Waiting For"

A Mother's Prayer - Rachel Aldous / Happy Mother's Day, baby lullaby, de...

Do You Want My Love

Before I Fall in Love by Coco Lee (with Lyrics)

Definition
Also known as Apps, this is a program or group of programs designed for end users. Apps are often referred to as "Software" and can be divided into two general classes: systems software and applications software. Systems software consists of low-level programs that interact with the computer at a very basic level. This includes operating systems, compilers, and utilities for managing computer resources.

In contrast, applications software (also called end-user programs) include database programs, word processors, and spreadsheets. Practically speaking, applications software resides above systems software, because it is unable to run without the operating system and system utilities.

[edit]Subclass of Software
As a subclass of computer software, applications software addresses the capabilities of a computer directly and comprehensively in tasks that the user wishes to perform.

The term application refers to both the software itself, as well as its implementation. Systems Software on the other hand, is rarely involved in direct user interaction. However, it does have a hand in the integration of the computer's various capabilities, and this, in turn, affects the User Experience.

For example, the Powergrid generation unit is a type of system software and its application, with a bulb used to light homes, factories, etc.

[edit]Types of Apps
Here are a few examples of types of software applications: word processors, spreadsheets, and media players. Application software often includes multiple applications bundled together as a package or suite, like Microsoft Office or OpenOffice which both contain a suite of applications for common office usage. There are many types of applications software.

[edit]Enterprise Apps
Enterprise software includes computer programs that assist in streamlining the business processes of an enterprise organization as well as managing its data flows, thereby channeling its decision support information in the operational and strategic areas of business management.

Examples of enterprise software include: Finance Management, Customer Relationship Management, and Supply Chain Management. Some examples of the enterprise software at operational level, including Expense Management, Logistics, Helpdesk for Customer Support, and Sales Network Management.

[edit]Enterprise Infrastructure Apps
Enterprise infrastructure software include software tools and packages which the Enterprise software systems can use for development. Some examples of typical Enterprise infrastructure software include: Databases, Email servers, Web design tools, Network Security Management software tools, and application testing tools.

[edit]Information Worker Apps
Information worker software includes software at an operational level, which is task-oriented and addresses the needs of the organization's staff in many of their day-to-day tasks. Some examples of these include, Documentation Management tools, Word Processing, Spreadsheets, Email and Chat Clients, Personal Information Systems, Time Management, and Resource Management.

[edit]Content Access Apps
Content access software includes general utility software packages, and tools that facilitate the access and use of digital content. Some examples of content access software include media players, web browsers, sound/graphic/video editing tools, computer games, and DVD and CD reader/writer software tools.

[edit]Educational Apps
Educational software includes software packages where the content is usually created with multimedia, which can be used for teaching and learning. Educational software packages can be interactive and collaborative using the SCORM standards. Some examples include digital dictionaries, encyclopedias, wikis, LMS based, children's learning (such as, Disney Interactive, Gcompris), professional learning software systems, and digital tutorials.

[edit]Simulation Apps
Simulation software is computer software that is primarily used for system modelling, system testing and for simulating physical or abstract systems for various purposes such as research, entertainment, testing, training, or demonstrations. Some examples of simulation software include computer gaming, software testing ( such as WebTest), facility design/configuration, scheduling (such as Arena from Rockwell Automation), event simulation for material handling (such as AutoMod), and capacity-planning simulation (like AutoSched AP.)

[edit]Media development Apps
Media development software is the software development tools and utilities that are used for creating software in electronic and print media, animations, gaming, websites, movie, and musicals. Some examples of media development software include graphic arts software (such as PhotoShop, Illustrator, ImageReady, and Gimp), Desktop Publishing software (like Pagemaker), multimedia development software (like Flash, Swish, HTML editors (such as Dreamweaver, HTML Kit, FrontPage), digital animation editors (like Gif Animator Set), digital audio (MIDI sequencers like GarageBand, Fl Studio, and Apple Logic) and video composition (like Swish, or Director.)

[edit]Product engineering Apps
Product engineering software are software packages and tools that are used in developing high end software systems (like system software, embedded software, IDEs, compiling tools, APIs, device drivers etc), developing computer hardware and engineering product design, and modeling. Product engineering software also includes specialized engineering design software such as CAD (Computer Aided Design), CAM (Computer Aided Manufacturing), and CAE (Computer Aided Engineering) tools.

General
An OS takes care for all input and output in a computer system. It manages users, processes, memory management, printing, telecommunication, networking etc.

It sends data to a disk, the printer, the screen and other peripherals connected to the computer

And because every machine is build different, commands for in or output will have to be treated differently too. In almost all cases an Operating System is not one large big behemoth but consists of many small system programs governed by the core or kernel of the OS. Because of the compactness of these small supporting programs it is easier to rewrite parts or packages of the OS than to redesign an entire program.

In general programmers only have to make a "call" to the system to make things happen

This not only makes their live less miserable but the production time becomes shorter. As well as that programs can run on different types of machines with the same family of CPU's without changing anything in the program. This is what makes a standard Operating System so important.

In fact any form of standardization is important for production and compatibility



Functions and Structure

Introduction

At first operating systems were designed to help applications interact with the computer hardware. While this is still the case, the importance of the operating system has grown to the point where (at least in the minds of many users) the operating system defines the machine. Most users engaged in the Mac - PC - Unix battle are arguing about the operating systems on these machines, not the hardware platform itself.


The operating system provides a layer of abstraction between the user and the bare machine. Users and applications do not see the hardware directly, but view it through the operating system.


This abstraction can be used to hide certain hardware details from users and applications. Thus, changes in the hardware are not seen by the user (even though the OS must accommodate them).


This is particularly advantageous for venders that want offer a consistent OS interface across an entire line of hardware platforms. For example, certain operations such as interaction with 3D graphics hardware can be controlled by the operating system. When an instruction pertaining to the hardware is executed and if the hardware is present then all is fine. However, if the hardware is not present then a trap is generated by the illegal instruction. In this case the OS can emulate the desired instruction in software.


Another way that abstraction can be used is to make related devices appear the same from the user point of view. For example, hard disks, floppy disks, CD-ROMs, and even tape are all very different media, but in many operating systems they appear the same to the user.


Unix, and increasingly Windows NT, take this abstraction even further. From a user and application programmer standpoint, Unix is Unix regardless of the CPU make and model. As previously mentioned, it is this feature of Unix more than any other that is responsible for Unix's popularity.


We can view an operating system as providing four basic interfaces:


interface to the underlying hardware


interface to application programs


interface to the user


interface to the system manager


Each of these interfaces provides the appropriate view for different groups of individuals:


hardware developers who want their hardware to be supported by a particular operating system are primarily interested in the OS-hardware interface.


application programmers are primarily interested in the OS-application interface.


ordinary users are interested in the user interface. Many books that purport to be about a particular operating system in fact mainly discuss the user interface.


system managers are obviously interested in the system management interface.
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Most operating systems in use today are composed of two distinct parts: the kernel and the system programs. The kernel is primarily responsible for the first two of the interfaces described above, and the system programs are primarily responsible for the last two.



Functionality of the Operating System Kernel



Processes.

A key abstraction utilized in the design of an operating system is the notion of process.


A process is a program in execution.


the status of a process includes:


the code that is executing


the values of its variables


the contents of the CPU registers, especially the program counter (PC)


the state of the process (running, ready, waiting, etc.)


At any given time, the system kernel is managing a collection of processes.


some are user processes (shells, applications, etc.)


some are system processes (print spooler, accounting process, etc.)


An important kernel function is the management of processes. The kernel is responsible for creating, scheduling and deleting processes and often for inter-process communication.


Resource Allocation.

Modern operating systems often provide users and applications with a virtual machine, an interface to the underlying hardware that makes it appear as though the user is the only user of the machine and it's hardware.


CPU.

Whether the computer has one CPU or several CPUs, it is usually the case that there are more processes than CPUs. Thus, the operating system is responsible for scheduling the processes on the CPU(s).


Memory.

There is a finite amount of memory that must be shared among the processes. The way this is done varies between different operating systems, but a commonly used mechanism is that of virtual memory.


IO devices.

Several different processes may be trying to access a single IO device and the operating system must manage these accesses. Note that this is a different issue than processes scheduling since often IO is being performed for processes that are not currently executing.


Some devices (e.g. disks) have resources that can be shared among users and/or user processes. The operating system is responsible for managing and protecting these resources.


Support Services. Another important operating system task is providing support services for processes. These include:


Support for IO operations. We've already discussed how the operating system controls IO to enforce a protection scheme.


File system management.


Networking.


Protection.
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Interrupts and Traps. A great deal of the kernel consists of code that is invoked as the result of a interrupt or a trap.


While the words "interrupt" and "trap" are often used interchangeably in the context of operating systems, there is a distinct difference between the two.


An interrupt is a CPU event that is triggered by some external device.


A trap is a CPU event that is triggered by a program. Traps are sometimes called software interrupts. They can be deliberately triggered by a special instruction, or they may be triggered by an illegal instruction or an attempt to access a restricted resource.


When an interrupt is triggered by an external device the hardware will save the the status of the currently executing process, switch to kernel mode, and enter a routine in the kernel.


This routine is a first level interrupt handler. It can either service the interrupt itself or wake up a process that has been waiting for the interrupt to occur.


When the handler finishes it usually causes the CPU to resume the processes that was interrupted. However, the operating system may schedule another process instead.


When an executing process requests a service from the kernel using a trap the process status information saved, the CPU is placed in kernel mode, and control passes to code in the kernel.


This kernel code is called the system service dispatcher. It examines parameters set before the trap was triggered, often information in specific CPU registers, to determine what action is required. Control then passes to the code that performs the desired action.


When the service is finished, control is returned to either the process that triggered the trap or some other process.


Traps can also be triggered by a fault. In this case the usual action is to terminate the offending process. It is possible on some systems for applications to register handlers that will be evoked when certain conditions occur -- such as a division by zero.



Operating System Design Principles
Operating system design is a complex task. One of the driving forces behind software engineering was the complexity of OS design. (See, for example, The Mythical Man Month by Frederick Brooks).
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System design goals:


User interface: should the interface be easy to learn by a novice user, or should it be designed for the convenience of an experienced user? (multiple user interfaces?)


Efficient system resource management. Unfortunately, the more complete the resource management, the more overhead.


Security. Once again, the more secure a system is the less efficient it is.


Flexibility. Most operating systems come preconfigured for many different devices. Part of the process of setting up a particular machine is to construct a version of the operating system that is tuned for the local installation. This tuning often involves setting certain limits, such as the maximum number of processes. It also involves specifying the attached hardware so that only the necessary drivers will be loaded. Some operating systems can load and unload drivers automatically at run-time.


Portability. Will the operating system be portable to widely varying types of hardware, or just different models of a particular class of hardware?


Backwards compatibility and emulation. Is it important that software that ran under previous operating system versions or under different operating systems be supported?
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Layered design:


Operating system consists of multiple layers. Each layer depends on the on the layer(s) beneath it.


Advantages: improved security, since only layers close to hardware need to operate in kernel mode.
improved portability since only small part of operating system interfaces with the hardware.
makes maintenance of operating system code easier.
Disadvantages: deciding what functionality to put in each layer can be difficult. This is because there are some interdependencies that would violate the layering model.decreased efficiency.




Distinction between mechanisms and policies:


a mechanism is a facility the system provides the system manager. For example, VMS allows the manager to control whether or not a given account can be logged in to over a network connection.


a policy is a decision made by the manager(s) about how to accomplish some goal. For example, a company may decide that it will not allow privileged accounts to be logged in to over a network connection.


mechanisms are the tools used to implement policies.

Virtual Machines


The concept of virtual machines is closely related to layering.



In a typical multi-user system, users are expected to know that the machine is shared by other users, and that resources such as devices are shared between all the users.


In virtual machine operating systems an addition layer of abstraction is placed between the users and the system so that it appears to the user that they are using a machine dedicated to them.


Usually it is the case that a more powerful machine is used to host several virtual machines. For example, the 80386 and later Intel CPUs supported virtual 8086 machines. Thus, an operating system designed for the 80386 could actually run several copies of MS-DOS and appear to the user to be several different PCs at the same time.


Another example of a virtual machine system is the IBM 370 running the VM operating system. This allowed users to work as if they had a dedicated (but smaller, less powerful) 370 completely at their disposal.



Stacked Job Batch Systems (mid 1950s - mid 1960s) (2)
A batch system is one in which jobs are bundled together with the instructions necessary to allow them to be processed without intervention.

The basic physical layout of the memory of a batch job computer is shown below:

Monitor (permanently resident)
User Space
(compilers, programs, data, etc.)



The monitor is system software that is responsible for interpreting and carrying out the instructions in the batch jobs. When the monitor starts a job, the entire computer is dedicated to the job, which then controlls the computer until it finishes.

A sample of several batch jobs might look like this:

$JOB user_spec ; identify the user for accounting purposes
$FORTRAN ; load the FORTRAN compiler
source program cards
$LOAD ; load the compiled program
$RUN ; run the program
data cards
$EOJ ; end of job

$JOB user_spec ; identify a new user
$LOAD application
$RUN
data
$EOJ




Often magnetic tapes and drums are used to store data and compiled programs, temporarely or permanent..

1. Advantages of batch systems move much of the work of the operator to the computer
increased performance since it was possible for job to start as soon as the previous job finished
2. Disadvantages turn-around time can be large from user standpoint
more difficult to debug program
due to lack of protection scheme, one batch job can affect pending jobs (read too many cards, etc)
a job could corrupt the monitor, thus affecting pending jobs
a job could enter an infinite loop





One of the major shortcomings of early batch systems is that there's no protection scheme to prevent one job from adversely affecting other jobs.

The solution to this brought a simple protection scheme, where certain memory (e.g. where the monitor resides) were made off-limits to user programs. This prevented user programs from corrupting the monitor.

To keep user programs from reading too many (or not enough) cards, the hardware is changed to allow the computer to operate in one of two modes: one for the monitor and one for the user programs. IO can only be performed in monitor mode, so that IO requests from the user programs are passed to the monitor. In this way, the monitor can keep a job from reading past it's on $EOJ card.

To prevent an infinite loop, a timer is added to the system and the $JOB card is modified so that a maximum execution time for the job is passed to the monitor. The computer will interrupt the job and return control to the monitor when this time is exceeded.


Spooling Batch Systems (mid 1960s - late 1970s)
One difficulty with simple batch systems is that the computer still needs to read the the deck of cards before it can begin to execute the job. This means that the CPU is idle (or nearly so) during these relatively slow operations.

Since it is faster to read from a magnetic tape than from a deck of cards, it became common for computer centers to have one or more less powerful computers in addition to there main computer. The smaller computers were used to read a decks of cards onto a tape, so that the tape would contain many batch jobs. This tape was then loaded on the main computer and the jobs on the tape were executed. The output from the jobs would be written to another tape which would then be removed and loaded on a less powerful computer to produce any hardcopy or other desired output.

It was a logical extension of the timer idea described above to have a timer that would only let jobs execute for a short time before interrupting them so that the monitor could start an IO operation. Since the IO operation could proceed while the CPU was crunching on a user program, little degradation in performance was noticed.

Since the computer can now perform IO in parallel with computation, it became possible to have the computer read a deck of cards to a tape, drum or disk and to write out to a tape printer while it was computing. This process is called SPOOLing: Simultaneous Peripheral Operation OnLine.

Spooling batch systems were the first and are the simplest of the multiprogramming systems.

One advantage of spooling batch systems was that the output from jobs was available as soon as the job completed, rather than only after all jobs in the current cycle were finished.


Multiprogramming Systems (1960s - present)
As machines with more and more memory became available, it was possible to extend the idea of multiprogramming (or multiprocessing) as used in spooling batch systems to create systems that would load several jobs into memory at once and cycle through them in some order, working on each one for a specified period of time.



Monitor (more like an operating system)
User program 1
User program 2
User porgram 3
User program 4



At this point the monitor is growing to the point where it begins to resemble a modern operating system. It is responsible for:

* starting user jobs
* spooling operations
* IO for user jobs
* switching between user jobs
* ensuring proper protection while doing the above

As a simple, yet common example, consider a machine that can run two jobs at once. Further, suppose that one job is IO intensive and that the other is CPU intensive. One way for the monitor to allocate CPU time between these jobs would be to divide time equally between them. However, the CPU would be idle much of the time the IO bound process was executing.

A good solution in this case is to allow the CPU bound process (the background job) to execute until the IO bound process (the foreground job) needs some CPU time, at which point the monitor permits it to run. Presumably it will soon need to do some IO and the monitor can return the CPU to the background job.


Timesharing Systems (1970s - present)
Back in the days of the "bare" computers without any operating system to speak of, the programmer had complete access to the machine. As hardware and software was developed to create monitors, simple and spooling batch systems and finally multiprogrammed systems, the separation between the user and the computer became more and more pronounced.

Users, and programmers in particular, longed to be able to "get to the machine" without having to go through the batch process. In the 1970s and especially in the 1980s this became possible two different ways.

The first involved timesharing or timeslicing. The idea of multiprogramming was extended to allow for multiple terminals to be connected to the computer, with each in-use terminal being associated with one or more jobs on the computer. The operating system is responsible for switching between the jobs, now often called processes, in such a way that favored user interaction. If the context-switches occurred quickly enough, the user had the impression that he or she had direct access to the computer.

Interactive processes are given a higher priority so that when IO is requested (e.g. a key is pressed), the associated process is quickly given control of the CPU so that it can process it. This is usually done through the use of an interrupt that causes the computer to realize that an IO event has occurred.

It should be mentioned that there are several different types of time sharing systems. One type is represented by computers like our VAX/VMS computers and UNIX workstations. In these computers entire processes are in memory (albeit virtual memory) and the computer switches between executing code in each of them. In other types of systems, such as airline reservation systems, a single application may actually do much of the timesharing between terminals. This way there does not need to be a different running program associated with each terminal.

Operating Systems for mini's and mainframe's
Major operating systems:

UNIX & variants

The further development of the B language was done by Ken Thompson. With which he wrote a series of programs to operate the machines he used. As a logical result of that the UNIX operating system was designed that will be released in 1973 by the BELL laboratories.

AIX for the IBM RS6000, powerpc

XENIX

HP-UX mips

S/390

VMS

NetBSD vax


Operating Systems for Microcomputers or Personal computers


The second way that programmers and users got back at the machine was the advent of personal computers around 1980. Finally computers became small enough and inexpensive enough that an individual could own one, and hence have complete access to it.

Major operating systems:

Apple OS

Apple OS X

Mac OS X for the powerpc

BEOS

CP/M

Computer Program for Micro computers

DOS - Disk Operating System

Most used names: MS-DOS - PC compatibles, PC-DOS - IBM and compatibles, TOS - Atari, DOS - Amiga and many others

MS = Microsoft; T stands for Tramiel, Atari's company president; PC stands for Personal Computer

MS-DOS as well as PC-DOS are both the most frequently used operating systems for PC's until Windows 95 comes along where it becomes integrated with a WIMP environment.

Both MS DOS and PC DOS have the same origin namely: QDOS.

Mid 1980 Seattle Computer Products asked Tim Patterson to develop an operating system that was capable of running the 8086 CPU card. Under time pressure Tim developed an operating system which structure not exactly shone through its clarity. He named it QDOS - Quick and Dirty Operating System. On the basis of this system he built another Operating System: 86-DOS which was published at the end of 1980. This new version had very few bugs and was liked because of its enhanced efficiency. Sales of this DOS version were favorable to the acceptation of this system. Also because the author had structured the system functions thus that they were the same as the popular CP/M system. For this reason manufacturers could adapt their machines which were thought for CP/M without any problems for 86-DOS. Also the limitations for programs running under CP/M were eliminated.

In 1981 IBM decided to build the Intel 8086 CPU into their PC's and looked around for an efficient operating system. IBM choose Microsoft who had bought the rights of 86-DOS by then. Under the leadership of Tim Patterson, who went together with his brainchild to Microsoft, programmers of Microsoft developed version 1 of MSDOS on prototypes of the IBM PC. IBM liked the system bought the license and introduced it together with its new machine in 1981. IBM called it PC-DOS.

This first version soon no longer satisfied users, also because of improved equipment that was marketed. Programmers agreed that should DOS be further developed an important property of this operating system should be that it remained compatible with its predecessors.

Compatibility will say that, aside from some technical factors, to what extend discs and data can be taken over from one system to another. If two systems are compatible data can be freely exchanged between the two. If systems are not compatible like the Commodore 64 and the IBM PC, data and discs can not be exchanged without having to convert one of the two.

The widespread use of the MS-DOS operating system is caused by this so called compatibility. This line of thought also took care of the future DOS developments.



GEM,

Introduced by Digital.

The Graphical Environment Manager (GEM) from Digital Research was really nice and fast. It's a pity that this firm lost the second battle (the first was CP/M versus DOS) against the boys from Redmond.

GEOS,

introduced in 1986 by Berkeley Softworks [1]

Unix & variants

FreeBSD i386

Linux i386, sparc, powerpc, alpha

OpenBSD i386, alpha, sparc

Solaris ultra sparc

Windows NT i386

MS Windows

Microsoft. In early version windows means a "look-something-like" graphic interface combined with DOS later versions consisted of an integrated (D)OS with a graphical interface

OS/2

IBM's version of a graphic interface

WIMP



Common features



Operating Systems for Supercomputers
[we need some help here!]



Major operating systems:

LINUX

UNIX





Common features
*



Real-Time, Multiprocessor, and Distributed/Networked Systems
A real-time computer is one that execute programs that are guaranteed to have an upper bound on tasks that they carry out. Usually it is desired that the upper bound be very small. Examples included guided missile systems and medical monitoring equipment. The operating system on real-time computers is severely constrained by the timing requirements.

Dedicated computers are special purpose computers that are used to perform only one or more tasks. Often these are real-time computers and include applications such as the guided missile mentioned above and the computer in modern cars that controls the fuel injection system.

A multiprocessor computer is one with more than one CPU. The category of multiprocessor computers can be divided into the following sub-categories:



shared memory multiprocessors have multiple CPUs, all with access to the same memory. Communication between the the processors is easy to implement, but care must be taken so that memory accesses are synchronized.


distributed memory multiprocessors also have multiple CPUs, but each CPU has it's own associated memory. Here, memory access synchronization is not a problem, but communication between the processors is often slow and complicated.

Related to multiprocessors are the following:

networked systems consist of multiple computers that are networked together, usually with a common operating system and shared resources. Users, however, are aware of the different computers that make up the system.


distributed systems also consist of multiple computers but differ from networked systems in that the multiple computers are transparent to the user. Often there are redundant resources and a sharing of the workload among the different computers, but this is all transparent to the user.

Computer Software

Computer software is the combination of programmes and applications which interface with the physical components of the computer, the hardware, to enable the user to perform specific functions and tasks. There are two basic types of software, known as system software, which is responsible for the basic functions of the computer, and application software, such as Word Processing programmes, which enable the user to perform actual specific tasks, e.g. typing.

An operating system is the software behind all of the system and application management; it is responsible for organising and controlling how each of the systems interface with each other (basically the smooth running of every programme), for example, allocating the appropriate amount of memory in accordance with which programmes are running and require more power and input. Examples of operating systems are Linux, and of course Microsoft Windows, which holds a monopoly on the computer market for such systems. Without an Operating system, computers are merely empty shells with little or no use. They will typically run their won application software, for example Microsoft Windows has packages such as Microsoft Office, which deals with word processing, publishing, presentation slides, databases, etc. Modern computers can run several applications simultaneously without crashing and becoming slow, depending on the power and capabilities of the operating system.

Software is constantly being up dated and new versions being released, so much so that current systems can become out of date within months - it is a very fast moving and fast evolving area of industry. Microsoft have just released their latest operating system to follow on from the roaring success of Windows XP; Vista. Packages available include Home Basic, Home Premium, Ultimate and Business. The main improvements and selling points of this service package include state of the art user interfaces (Aero - Authentic, Energetic, Reflective and Open), easier transfer of media between devices and computers, better security (virus protection, etc) and new multimedia programmes. For example, Windows Media Player 11 is included in the package and has undergone a major revamp; including user interfacing, new search capabilities, and the facility too hook up with external devices such as the Xbox 360.

However, many consumers are fully aware of Microsoft's dominance in the computer industry and in particular the software market, and are reluctant to shell out for the new programme where many of the new features are seen as luxuries rather than necessities, and on top of that Vista cannot be installed on any machine - brand new machines must be purchased with the system already built in. So potential customers will have to buy a whole new PC setup just to be able to use Microsoft Vista - not a popular choice amongst consumers in an industry where there will doubtless be further improvements and new, better software waiting just around the corner. An advantage gained then, for rival Linux, whose majority of software CD's and packages can be accessed for free, so whilst it is a lot more complex and less user friendly than the likes of Microsoft and their Windows packages, yet it remains one of the most reliable and up to date operating systems out there.

Computer parts and components

Basic Components:


CPU:
Central Processing Unit. The most powerful microprocessor chip in your computer is the CPU. For example the Intel Pentium chip handles the central management functions of a high-powered PC. Intel's newest Hyper-Threading (technology that allows the CPU to process two separate threads of data simultaneously) CPU supports a 1 megabyte on-board L2 cache (the on-board cache functions as a buffer to feed data to the CPU at a faster rate). The speed of the CPU is measured in GigaHertz (billions of cycles per second).
Recommendation:
Good: Intel Pentium Celeron D - 2.6 GigaHertz or higher.
Power User: Intel Pentium 4 with Hyper-Threading Technology - 3.0 GigaHertz or higher, or Intel Pentium D - Dual Core - 3.0 GigaHerz or higher.



RAM:
Random-Access Memory. Hardware inside your computer that stores information while you work. RAM is one of the things that makes your computer run faster. RAM is not permanent storage of data. When you turn your computer off, all data in RAM is lost. RAM is available in different types, sizes, and speeds. Currently, depending on the Motherboard, the Intel Celeron D CPU uses PC-2700 ram with 533 MHz FSB (Front Side Bus). The Intel Pentuim 4 HT CPU uses PC-3200 DDR (double data rate) ram with 800 MHz Front Side Bus.
Recommendation:
Good: 256 to 512 MegaBytes
Power User: 1 to 2 GigaBytes



Hard Drive:
A Data Storage medium that houses all of the information in your computer. This would include your operating system (Windows), device drivers, programs, and data you have created using your programs (word documents, spread sheets, etc.). Unlike RAM the Hard Drive retains data when the computer is turned off. Hard Drives sizes are in GigaBytes or billions of characters. EIDE hard drives spin at a speed of 7200 RPM. Older EIDE hard drives spin at 5400 RPM. New technology hard drives are now on the market, and these are SATA (Serial ATA) hard drives. Currently, these SATA hard drives have speeds approximately the same as EIDE. Looking ahead, the SATA hard drives will be faster and the prices will drop. The SATA hard drives require different MotherBoard technology to support them.
Recommendation:
Good: 40/80 GigaBytes (minimum) Western Digital Caviar Ultra DMA 7200 RPM Hard Drive
Power User: 80/250 GigaBytes Western Digital SATA Hard Drive



MotherBoard:
The main circuit board of the computer. All key internal and external components of your computer plug into the MotherBoard, such as the CPU, RAM, Hard Drive, etc. The speed at which information travels across the MotherBoard is referred to as the BUS speed. Recently a new technology has been introduced called PCI Express. This allows a faster data transfer speed across the MotherBoard, especially for video graphics.
Recommendation: Good: Asus or Intel MotherBoard with the Intel 865 Chipset (minimum) supporting 800 MHz System Bus speed and USB 2.0
Power User: Asus or Intel Motherboard supporting P4 Hyper-Threading and Dual Core technology with with PCI Express support and SATA and EIDE Hard Drive support.



Case:
Often called the "computer", the case houses and provides power to the major computer components, including the MotherBoard, CPU, Hard Drive, RAM, Video Card, Sound Card, etc. Those components not housed in the computer case are usually referred to as "peripherals". The case also houses the power supply. It is important to have a large enough power supply to handle your current and future needs. Also important is that the case be large enough and have enough ball bearing fans so the internal components do not overheat and cause damage to themselves. Miniature cases are to be avoided. Never put your computer in a desk compartment or other small space where it can't breathe. Heat is the enemy of all computers.
Recommendation: Good: Mid or Full Tower Case with 300 Watt Power Supply
Power User: Mid or Full Tower Case with 420 Watt Power Supply and at least two internal ball bearing fans. With fans, more is better.



Monitor:
The video display unit that sits on your desktop and serves as your computer screen. Monitors are available in two basic types. The CRT (cathode ray tube - looks like a TV set), called "flat" or "perfect flat" and the LCD (liquid crystal display) called "flat panel"- pictured on the left. The LCD Flat Panel monitors are more expensive, but have a smaller footprint on your desktop. The better LCD monitors can support digital (better) or analog input from the video card. With LCD Monitors we must watch closely the "response time". This is how fast the monitor redraws the picture. If you get a LCD with a slow refresh rate, some video or games may be jerky to watch.
Be careful when you buy - rebuilt or refurbished monitors may be called "new" and have a one year warranty. You want a "brand new" monitor with a three year warranty.

Recommendation: Good: 17" CRT Flat or Perfect Flat model
Power User: 17" or 19" LCD with Digital and Analog inputs and 8 ms or less response time.



Video Card:
A circuit board that plugs into a MotherBoard slot, usually an AGP (accelerated graphics port) slot or PCI Express slot (newer/faster/more bandwidth) and handles multimedia applications and graphics-intensive web sites freeing up the CPU (thereby increasing your computers speed). The monitor plugs into the video card which is accessed thru a slot in the back of your computer. The better the graphics chip on the video card, and the more ram built on the video card, the faster the display on the monitor. Top of the line games need very high performance video cards. Better Video Cards have both Digital (better) and Analog outputs.
Video Cards that are built onto the MotherBoard and cannot be upgraded are to be avoided.

Recommendation: Good: AGP or PCI Express Video Card with good graphics chip (ATI) and at least 32 MegaBytes of RAM on board.
Power User: ATI Radeon PCI Express with at least 128 Megs of DDR (double data rate) RAM and Digital and Analog outputs.



Speakers:
Produce sound (music, voice, etc.) based on data created and sent by the sound card. Today, computer speakers have become very high quality and many include a sub-woofer for good bass.
Recommendation: Good: Altec Lansing stereo speakers.
Power User: Altec Lansing 2.1 (2 stereo speakers, 1 sub-woofer) or better.



Sound Card:
A circuit board that plugs into your MotherBoard that adds audio capability to your computer, providing high quality stereo output to the speakers.
Recommendation: Good: Creative Labs Sound Blaster Live or Integrated Sound Card (built on MotherBoard)
Power User: Creative Labs Sound Blaster Audigy II or better.



CD-ROM:
Compact Disk - Read Only Memory. An optical storage technology that stores and plays back data. "Read Only" means the information can be displayed and used or copied, but cannot be deleted or changed (on the disk). One CD-ROM can hold around 650 megabytes of data, or the equivalent of 450 floppies. The speed of a CD-ROM refers to how fast the disk spins in the device.
Recommendation: Good and Power User: Any high quality unit with a speed or 52x. Example: LiteOn 52x CD-ROM.


CD-Burner or DVD/CD Burner A CD Burner is the informal name for a CD recorder, a device that can record data to a compact disc. CD-Recordable (CD-R) and CD-Rewritable (CD-RW) are the two most common types of drives that can write CD's, either once (in the case of the CD-R) or repeatedly (in the case of the CD-RW). In the CD-R recording process, the data is actually etched into the disc (burned) with a laser. In the CD-RW process the disk must first be formatted (burned) and then data is copied to or erased from the CD-RW media. Almost all burners can do both tasks - record (CD-R) and rewrite (CD-RW). The best way to determine this is from the specs. "52x32x52a" would be a spec for a current burner. The 52x means the record speed (CD-R), the 32x means the rewrite speed (CD-RW) and the 52a (a = average) means the read speed. If you have a CD-Burner, then a separate CD-ROM is not necessary.
The DVD Burners read, write, and re-write to DVD,s and read, write, and re-write to CD's. If you have a DVD Burner, then a separate CD-Burner is not necessary.

Recommendation: Good: LiteON 52x32x52a CD-R, CD-RW, CD-ROM
Power User: LiteOn 16x DVD-R, DVD-RW, DVD-ROM - also supports +R, +RW, and +R Double Layer.



Modem:
A circuit board that plugs into your MotherBoard that enables your computer to communicate with other computers and the Internet. Phone lines are "analog" and computers are "digital" so the modem has the job to MOdulate and DEModulate between analog and digital, thus the name MODEM.
Special Note: For today's Internet User the old telephone modems are all but obsolete - try to obtain Cable or DSL Internet service.

Recommendation: Good and Power User: A 56K - V.92 internal modem. The 56K refers to speed and the V.92 refers to error correction. The error correction is very important as phone lines get older and lose their quality,
Ethernet Card:
A circuit board that plugs into your MotherBoard and provides the capability to connect or "Network" your computer to other computers and/or the Internet. If you use a cable modem, your computer will need an Ethernet card. Ethernet cards come in different speeds. A 10 Mbps card can transmit/receive at 10 million bits (8 bits to a byte) per second. A 10/100/1000 Mbps card can transmit/receive at up to 1000 million bits per second.
Recommendation: Good and Power User: A 10/100/1000 Mbps Ethernet Card. Example


Keyboard:
The peripheral device used to input information into a computer. It provides a set of alphabetic, numeric, punctuation, symbol and control keys. When a character is pressed, it sends a coded input to the computer, which then displays the character on the Monitor. Keyboards are available in corded and wireless models. Keyboards should come with a wrist rest.
Recommendation: Good and Power User: 104 key (minimum) Keyboard with a wrist rest - either corded or wireless. Examples: Logitech or Microsoft.
Mouse:
A peripheral device connected to your computer, used to reposition the cursor or move the pointer on your screen. A mouse usually has at least two buttons, you can use to highlight text, open menu items, launch programs, etc. A mouse can be corded or wireless. Some mice have a ball on the bottom that rolls as you push the mouse, and some mice have optical function. No ball, the mouse senses the movement by an optical beam it emits. There is no need for a mousepad with an optical mouse.
Recommendation: Good and Power User: A high quality "optical" mouse, with at least 2 buttons, either corded or cordless. Examples: Microsoft or Logitech
Floppy Drive:
A device in your computer that allows removable (a floppy disk) storage. Data can be written to or read from a floppy disk in a floppy drive. Each floppy disk can be removed, so you can store data on more than one disk.
Recommendation: Good and Power User: A high quality floppy drive that accepts 3.5 inch floppy disks. Each floppy disk should hold a minimum of 1.44 megabytes of data.
Operating System:
The foundation software of a computer system. Responsible for controlling and launching the installed applications and computer peripherals. It schedules tasks, allocates storage, handles the interface to peripheral hardware and presents a "default" interface to the user when no application program is running.
Recommendation: Good and Power User: Microsoft WindowsXP Home Edition with SP2 (Service Pack 2) or Microsoft WindowsXP Professional Edition with SP2. The main difference between Home and Professional is that Professional can network with a "domain" - or 10,000 other computers (Client/Server Environment), while Home can only operate in a Peer to Peer networking environment (recommended 5 computers or less). Home is perfect for the home or small office (called SOHO - Small Office Home Office). Professional is needed for larger businesses and for software applications that require Client/Server environments. WindowsXP Professional is more expensive than WindowsXP Home.
WindowsXP Media Center Edition is recommended for those users who want to include full media capabilities to their computer.

We are living in an information age dependent upon digital information. Digital information is electronic information, the result of computer processing. Every type of job relies upon getting information, using it, managing it, and relaying information to others. Computers enable the efficient processing and storage of information.

Do not think of a computer merely as the machine with the keyboard and the mouse, although that might be true for some types of computers. Embedded computers may be inside your household appliances, the VCR, the automobile, planes, trains, powerplants, water purification plants, calculators, and even inside a few toys. These embedded computers are very small. They affect our lives each day. Why, even modern traffic lights operate with computers. They are all around us. Think of additional ways in which computers affect our lives each day.



The Four Operations of a Computer System
Input
Home computers are microcomputers. Input is supplied to the microcomputer with the use of a keyboard, a mouse, or another input device. These input devices may be called peripheral devices.
Processing
Processing is done inside the computer in an area called the central processing unit (CPU). Processing is the conversion of input to output.
Storage
Storage refers to holding information somewhere.
RAM, Random Access Memory, is short-term memory. It is volatile memory because the memory is automatically "erased" when the power is turned off or interrupted. The RAM memory is located inside the computer case on the motherboard. A motherboard is not the keyboard. The keyboard is what you type with. A motherboard holds RAM memory, electronic circuits and other computer parts including the central processing unit. ROM, Read-Only-Memory, is not volatile meaning the memory is still there when power is interrupted or turned off. When the computer is turned back on again, ROM memory is still in storage on the internal hard disk.
Output
Output is the result of a computer process. Output may be viewed on a monitor screen, heard through speakers, printed on printers, and so forth. Output devices may be considered hardware and are also considered to be peripheral devices.





A Basic Computer "System"
A computer system refers to the computer AND all of its equipment. Equipment like speakers, printer, keyboard, scanner, etc. is called peripheral equipment, sometimes shortened to "peripherals". The central processing unit (CPU) is considered to be "the computer". Without peripheral equipment (such as monitor, printer, speakers, etc.) for input and output the microcomputer (home computer) will not be able to do anything you find useful.

Your computer system cannot help you type a letter unless you have some type of software (program) to do this. Most typing is handled by a "word processing" program. A software program for your computer can be purchased at stores like Office Depot, Staples, and computer stores. Check your local telephone directory for a computer store in your area. Sometimes when you purchase a computer it already has a word processing program installed. If you buy a computer from a large electronics chain store, even if you have to travel out of town, you will get a better price as a rule than buying from a smaller chain store in town. Ask in town first, if they would be willing to match another store's Advertised price... See "Buying A Computer", next.





Buying A Computer
It is best to ask and to compare features before you buy a computer. The first question to ask yourself is, "What do I want a computer to do?" Do you need it only for e-mail and a little light letter writing or do you need it for graphics and Web page authoring? Will you also want extra storage for your music files or graphics files? Do you need any hardware for game playing? What type of Internet connection will you have: dialup, cable, DSL, or other broadband connection? Will you be needing a computer for school work? Accounting? Make a list of what you need the computer to do before you talk to anyone about purchasing a computer. Your needs will be different that those of the next person. Visit Computer Company Web sites.





The PC vs. The Macintosh
There are several computer systems available for home computing but the two most common types of computers are the PC (personal computer), manufactured by companies such as DELL, IBM, NEC, GATEWAY, HP, SAMSUNG, and others -- and the Macintosh manufactured by Apple Computer.
The Macintosh Computer
The Macintosh computer is commonly referred to as a "Mac". Apple Computer has produced a PowerMac, an iMac, and a PowerMac G4, and the PowerMacG5. The operating system of the PowerMac G4 or G5 has undergone revisions. Each major version also has a name: OS X version 10.2.x is Jaguar; version 10.3.x is Panther, and the version 10.4.x is Tiger. The Apple PowerMac computers(the G4 and the G5) have two processors (for parallel processing) instead of just one, and there is space inside the computer to upgrade to 4 hard disks in a RAID array to give more power to the computers functioning as a server. Sometimes the computer tower is called a "box" which is a slang word for "the computer". You could say, "there are two processors inside the box."

There is software specially designed for the PowerMac computers to help move files from a Windows 98, ME, or 2000 system (XP is not listed on the box) to the Mac OS X. This software is called Move2Mac and is a product of Detto Technologies. I found my copy of the shrink-wrapped software on a shelf at a large Fry's Electronics store. A lot of computer software can be purchased using a credit card with a secure connection over the Web, then downloading that software to your own computer. I prefer having a CD or other disk with the software on the disk.

Downloading via FTP is the process of moving files from another computer over a network connection to a local computer (like your own home computer) using File Transfer Protocol (FTP). If working at school or on the job you have to get permission to download files, for security reasons. You can download files using a Mac or a PC computer. Both use File Transfer Protocol.

The Macintosh has excelled in the commercial graphics and publishing industries and thousands of people prefer a Mac for home use rather than a PC. The PC computers currently have a much greater market share and there are millions in use in homes and businesses throughout the world. When you attend college the college will specify which type of computer, Mac or PC, will be in use at the college for faculty and students. Some colleges use just Mac computers in campus buildings and for the faculty. Other colleges use PCs.

Each PC running a specific operating system such as Windows 2000 is able to use any software that says WIN95/98/NT/2000 on the box. The Windows2000 operating system can also run any software specified for WIN95/98/NT/2000 as well as any software specified as Windows 9.x/NT/2000. If in doubt about buying the correct software for your system, the store clerks will be happy to assist you if asked. If you are using Windows XP, make sure that the software you buy has Windows XP included in the "System Requirements", usually found on the side panel of the box for shrink-wrapped software (boxed software).

(In the following paragraphs I use OS to mean "operating system")
Prior to the Macintosh OS X operating system the Macs used an operating system based upon a single processor (computer CPU) which processed data and ran applications using what was called cooperative multitasking. Cooperative multitasking allowed programs to sometimes take control of the central processing unit. Now with the newer Macintosh operating system, OS 10.2.x (Jaguar) and later versions there is a UNIX-like kernel in the operating system, two processors and the central processing unit processes data with symmetric multiprocessing (uses both CPU's or "chips" to process data) and it uses preemptive multitasking, not allowing any application to take control of the central processing units.

If users want to run older software, the PowerMac G4 is a dual-booting machine meaning you can either boot into the older OS 9.2 or a version of OS X. (This is called "dual bootable".) Software written for the OS X (pronounced OS ten) will not run in the OS 9 environment but older legacy software is capable of being run while booted into the newer OS X, just that the newer features of the OS X will not be available when running applications designed for the OS 9 or older operating systems. The Mac G5's and newer versions of Os X have more multimedia features than the earlier G4's with the older versions of OS X. Get to the Apple Computer Web site for what's new now. The computer industry is not standing still... changes are rapid and one article online cannot capture what is now current.



Central Processing Unit and Software Compatibility
The computer processor inside a PC or PC-clone computer has totally different architecture (microscopic "wiring" schematic) inside the central processing unit chip (the CPU, or "chip"). In other words, the specific way the circuits are laid out in a computer chip (CPU, central processing unit) is called the chip architecture. PC chips and Mac chips have processing units with totally different architecture. Software is not interchangeable. Buy Mac software for the Macintosh and buy PC software for PC computers. An Apple or Mac computer is not a PC. Most PC Computers are sold new with a Windows operating system but keep in mind that other operating systems can also run on PC-architecture machines. One example of another operating system that can run on a PC machine is Linux for Windows. When two operating systems are on a disk they are installed on separate "partitions" of the disk. That is similar to two songs on one CD having to be on separate "tracks".



Hardware and Software
Usually, things you can see and touch on a computer or inside a computer are called "hardware" whereas programs for the computer (digital instructions) are called software. Software is created by a computer programmer who writes lines of code for the computer. An interpreter or compiler is a smaller program which changes the programmer's code into machine instructions for the central processing unit. After much testing and debugging, the programmer's code is finally "packaged" into executable files which make up the final "software" which can be purchased later, or might be "bundled" with the computer when you buy it (meaning that some software is already installed when you buy the computer.)

Work Station

A type of computer used for engineering applications (CAD/CAM), desktop publishing , software development and other types of application that require a moderate amount of computing power and relatively high quality capabilities.

Workstations generally come with a large, high-resolution graphics screen, at least 64 MB (megabytes) of RAM, built- in network support and a graphical user interface. Most workstations also have a mass storage device such as a disk drive, but a special type of workstation, called a diskless workstation, comes without a disk drive. The most common operating systems for workstations are UNIX and Windos NT.

In terms of computing power, workstations lie between personal computers and minicomputers, although the line is fuzzy on both ends. High-end personal computers are equivalent to low-end workstations, and high-end workstations are equivalent to minicomputers.

Maincomputer

Small desktop or portable computer, typically designed to be used by one person at a time, although indivudual computers can be linked in a network so that users can share data and programmes. Its central processing unit is a microprocessor, contained on a single integrated circuit.

Microcomputers are the smallest of the four classes of computer (the others are supercomputer,mainframe and minicomputer). Since the appearance in 1975 of the first commercially available microcomputer, the Altair 8800, micros have become ubiquitous in commerce, industry and education.

Minicomputer

Minicomputer is a midsized computer.

Mainframes

Mainframes are designed to handle very high volume input and output (O/I) and emphasize throughout computing. It is used mainly, by large organizations for critical applications, typically bulk data processing, industry and consumer statistics, ERP and financial transaction processing. The term problaby originated fromthe early mainframes, as they were housed in enormous, room-sized metal boxes or frames. Later the term was used to distinguish high-end commercial machines from less powerful units which were often contained in smaller packages. Today in pratice,the term usually refers to computers compatible with the IBM System/360 line, first introduced in 1965. (IBM System z9 is IBM's latest incarnation.) Otherwise, systems with similar functionality but not based on the IBM System/360 are referred to as "servers". However, "sever" and "mainframe" are different (see client-server).

Types Of Computer

SUPERCOMPUTER

Supercomputer is a computer that led the world (or was close to doing so) in terms of processing capacity, particularly the speed of calculation, at the same time of its introduction. The term "Super Computing" was first used by the New York World newspaper in 1929 to refer to large custom-built tabulators IBM made for Columbia University. It was used to solve problems involving by major universities, military agencies and scientific research laboratories.

Computers Labs Rules and Regulations

1. Pupils are prohibited to enter the lab unless authorised by the teacher.
2. Scan diskettes before using them.
3. Report all problems related to the system to the teacher.
4. Do not attempt to repair or tamper with lab equipment.
5. Be responsible when using equipment, software and facilities in the lab.
6. Do not move any equipment from its original position.
7. Do not remove or load any software into the computer.
8. Do not change the settings in the computer.
9. Save all work in external storage device and not in the computer.
10. Do not bring in bags, food and drink into the lab.
11. Turn off the computer accordingly after use.
12. Switch off all power supplies before leaving the lab.
13. Internet facility is strictly for educational purposes only.
14. Teachers should record the use of computer lab in tne lab log book.
15. All users should record the use of computers in the computer log book.
16. The lab should be kept clean and tidy at all times.

Computer Parts And Components

A peripheral is a device attached to a host computer but not part of it whose primary functionality is dependant upon the host, and can therefore be considered as expanding the host's capabilities, while not forming part of the system's core architecture.

Examples are printers, scanners, tape drives, microphones, speakers, webcams, and cameras.

An input device is any peripheral ( piece of computer hardware equipment ) used to provide data and control signals to an information processing system ( such as a computer ). Input and output devices make up the hardware interface between a computer as a scanner or 6DOF controller.

An output device is any piece of computer hardware equipment used to communicate the results of data processing carried out by an information processing system ( such as a computer ) to the outside world.

In computing, input/output, or 1/0, refers to the communication between an information processing system ( such as a system ), and the outside world. Inputs are the signals or data sent to the system, and outputs are the signals or data sent by the system to the outside.

Examples of output devices: Speakers, Headphones, Screen ( Monitor), Printer

In computer hardware, a ' port ' serves as an interface between the computer and the other computers or peripheral devices. Physically, a port is a specialized outlet on a piece of equipment to which a plug or cable connects. Electronically, the several conductors making up the outlet provide a signal transfer between devices.

Fifth Generation ( Present and Beyond ) Artificial Intelligence

Fifth generation computing devices, based on artificial intelligence, are still in development, though there are some applications, such as voice recognition, that are being used today. The use of parallel processing and superconductors is helping to make artificial intelligence a reality. Quantum computation and molecular and nanotechnology will radically change the face computers in years to come. The goal of fifth-generation computing is to develo[p devices that respond to natural language input and are capable of learning and self-organization.

Fourth Generation ( 1971-Present ) Microprocessors

The microprocessor brought the fourth generation of computers, as thousands of intergrated circuits were built onto a single silicon chip. What in the first generation filled an entire room could now fit in the palm of the hand. The Intel 4004 chip, developed in 1971, located all the components if the computer-from the central processing unit and memory to input/ouput controls-on a single chip.

In 1981 IBM introduced its first computer for the home user, and in 1984 Apple introduced the Macintosh. Microprocessors also moved out of the realm of desktop computers and into many areas of life as more and more everyday products began to use microprocessors.

As these small computers became more powerful, they could be linked together to form networks, which eventually led to the development of the internet. Fourth generation computers also saw the development of GUIS, the mouse and handheld devices.

Third Generation ( 1964-1971 ) Intergrated Circuits

The development of the intergrated circuit was the hallmark of the third generation of computers. Transistors were miniaturized and placed on silicon chips, called semiconductors, which drastically increased the speed and efficiency of computers.

Instead of punched cards and printouts, users interacted with third generation computers through keyboards and monitors and interfaced with an operating system, which allowed the device to run many different applications at one time with a central program that monitored the memory. Computers for the first time became accessible to a mass audience because they were smaller and cheaper than their predecessors.

Second Generation ( 1956-1963 ) Transistors

Transistors replaced vacuum tubes and ushered in the second generation of computers. The transistors was invented in 1947 but did not see widespread use in computers until the late 1950s. The transistors was far superior to the vacuum tube, allowing computers to become smaller, faster, cheaper, more energy-efficient and more reliable than their first-generation prodecessosrs. Though the transistor still generated a great deal of heat that subjected the computer to damage, it was a vast improvement over the vacuum tube. Second-generation computers still relied on punched cards for input and printouts for output.

Second-generation computers moved from cryptic binary machine language to symbolic, or assembly, languages, which allowed programmers to specify instructions in words. High-level programming languages were also being developed at this time, such as early versions of COBOL and FORTAN. These were also the first computers that stored their instructions in their memory, which moved from a magnetic drum to magnetic core technology.

The first generation computers of this generation were developed for the atomic energy industry.

Computer History

First Generation ( 1940-1956 ) Vacuum Tubes

The first computers used vacuum tubes for circuitry and magnetic drums for memory, and were often enormous taking up entire rooms. They were very expensive to operate and in addition to using a great deal of electricity , generated a lot of heat , which was often the cause of malfunctions.

First generation computers relied on machine language , the lowest-level programming language understood by computers , to perform operations , and they could only solve one problem at a time. Input was based on punched cards and paper tape , and output was displayed on printouts.

The UNIVAC and ENIAC computers are examples of first-generation computing devices. The UNIVAC was the first commercial computer delivered to a buisness client , the U.S. Census Bureau in 1951.

Exam over!!!!!!!!!!

(5/3/2010)Cheers,exam finally over!!What a happy day.The whole exam week was so boring,just eat,bath,study,eat,bath,study............haiz,don noe wat to say about this boring life.Don't know what to write already.Before that, i wanted to wish good luck to those who haven't started their exam yet.Wish u all can get a good result. Work hard......................

an unlucky day

This morning when i am on the journey to school,my mom's car broke down. One of the tyres punctured. So mum stopped her car side road. We waited for father to come rescue us. Late to school but so lucky, the prefects din record our name as late-comers.(1/3/2010).

hate exam

i'm having exam on monday(1/3).hav to study,so boring........n it lasts for five days.Haiz hav to work hard to get good results.Waiting for the the holidays to come.....

happy birthday

Happy belated birthday to thurga,may u will be healthier n eat more a bit.So that u won't be so skinny.

hope i have a suprised birthday

(16/1)my birthday is on tomorrow, i'm getting so excited.wish tomorrow i will have a suprised and happy 'bithday'!i have nothing to write edy,i gotta go

alyssa is here

This is my first time to write blog,i'm so excited.it's kinda fun.Wish someone will know me.By the way,my birthday is on this sunday(17/1)hope someone will give me presents or maybe greetings..................

A boring day

Today is quite boring at school.Especially sejarah lessons, i felt so sleepy. i saw some of my classmates did geography homework when teacher was teaching.at that time, i was worrying for my art work. I forgot to bring colour paper to do the front page of the sketch book.I so scared that the teacher will scold me.Luckily, she didn't notice.Haiz, the whole day for me is so boring and i always felt sleepy............that's all!