THE COMPUTER A computer system is the synthesis of

hardware and software. A typical computer system employs a computer that uses programmable devices to store, retrieve, and process data.

The personal computer or PC exemplifies one example of a computer system. An Automatic Teller Machine (ATM) is another example of a computer system.

The Internet does NOT exemplify a computer system per se, but rather a network of computer networks.

1. Hardware•Computer hardware is the physical part of a computer, including the digital circuitry, as distinguished from the computer software that executes within the hardware. •The hardware of a computer is infrequently changed, in comparison with software and data, which are "soft" in the sense that they are readily created, modified or erased on the computer. Firmware

• is a special type of software that rarely, if ever, needs to be changed and so is stored on hardware devices such as read-only memory (ROM) where it is not readily changed (and is therefore "firm" rather than just "soft").

2. Uses

•Personal computers are normally operated by one user at a time to perform such general purpose tasks as word processing, internet browsing, e-mail and other digital messaging, multimedia playback, video game play, computer programming, etc.

3. Categories of Personal computers as to size and portability:

a. Desktop Computer This is an independent personal computer that is made especially for use on a desk in an office or s used mainly to distinguish this type of personal computer from portable computers and laptops, but also to distinguish other types of computers like the PDA, server or mainframe.

All-in-one

• All-in-one computers are desktop computers that combine the monitor into the same case as the CPU.

•The term, "all-in-one" was initially associated with Digital Equipment Corporation's VAX "all-in-one" software which provided a common menu to choose: email, spreadsheet, database, file system, etc

b. Laptop

A laptop computer or simply laptop (also notebook computer or notebook) is a small mobile personal computer, usually weighing from one to three kilograms, depending on size, materials and other factors.

.Personal Digital Assistant

Personal digital assistants (usually abbreviated to PDAs) are handheld devices that were originally designed as personal organizers, but became much more versatile over the years. A basic PDA usually includes date book, address book, task list, memo pad, clock, and calculator software. Newer PDAs also have both color screens and audio capabilities, enabling them to be used as mobile phones (PDA Phone), web browsers or media players. Many PDAs can access the Internet, intranets or extranets via Wi-Fi, or Wireless Wide-Area Networks (WWANs).

d.Portable Computer

A Portable computer is a computer that is designed to be moved from one place to another (in other words, it is a computer that is portable). Portable computers, by their nature, are microcomputers.

Early portables were unkindly referred to as "luggables," referring to their great size and weight (owing partly to the need to include a full-blown CRT monitor, as LCD technology was not yet mature).

e. Tablet PC

A tablet PC is a notebook- or slate-shaped mobile computer.

Its touch screen or digitizing tablet technology allows the user to operate the computer with a stylus or digital pen instead of a keyboard or mouse.

A user can input text using the built-in handwriting recognition, on-screen (virtual) keyboard, speech recognition, or a physical

f. Wearable computer

A wearable computer is a small portable computer that is designed to be worn on the body during use. In this wearable computers differ from PDAs, which are designed for hand-held use, although the distinction can sometimes be a blurry one.

Wearable computers are usually either integrated into the user's clothing or can be attached to the body through some other means, like a wristband.

They may also be integrated into everyday objects that are constantly worn on the body, like a wrist watch or a hands-free cell phone.

4. Software

The software is the information that the computer uses to get the job done.

Software needs to be accessed before it can be used. There are many terms used for process of accessing software including running, executing, starting up, opening, and others.

The three basic types of software are:

commercial, shareware and open source software. Some software are also released into the public domain without a license.

•Commercial software comes prepackaged and is available from software stores and through the Internet.

• Shareware

is software developed by individual and small companies that cannot afford to market their software world wide or by a company that wants to release a demonstration version of their commercial product.

You will have an evaluation period in which you can decide whether to purchase the product or not. Shareware software often is disabled in some way and has a notice attached to explain the legal requirements for using the product.

•Open Source software

is created by generous programmers and released into the public domain for public use. There is usually a copyright notice that must remain with the software product.

Open Source software is not public domain in that the company or individual that develops the software retains ownership of the program but the software can be used freely.

Many popular Open Source applications are being developed and upgraded regularly by individuals and companies that believe in the Open Source concept.

Types of MemoryRAM - random access memory, also known as Read-Write memory, can have new data written into it as well as stored data read from it. A drawback of RAM is that it requires electrical power to maintain data storage. If the computer is turned off or looses power, all data stored in RAM is lost, unless if the data was saved to disk ROM - read-only memory, computer memory on which data has been prerecorded; once data has been written onto a ROM chip, it cannot be removed and can only be read

5. Disk and Storage

Disks are used to store information. Information on computers are stored in files. The size of a file is measured in bytes.

A byte is approximately one character (letter 'a', number '1', symbol '?' etc....).

•About a thousand bytes is a kilobyte (KB). •About a million bytes is a megabyte (MB). •About a billion bytes is a gigabyte (GB).

A byte is made up of 8 bits. A bit is simply an on or an off signal which passes through the computers circuitry. Every piece of software can be broken down into a series of on or off signals or its Binary Code.•Floppy disks are still a common way of transporting information (such as bringing files home from work) but compact disks (CDs) and Digital Video Devices (DVDs) are becoming more popular. Most software are sold on CDs. • Hard disks are the most common storage device.

Basic Computer Operations

How Computers Work Input: Information and programs are entered into the computer through Input devices such as the keyboard, disks, or through other computers via network connections or modems connected to the Internet. The input device also retrieves information off disks.

Output: Output Devices displays information on the screen (monitor) or the printer and sends information to other computers. They also display messages about what errors may have occurred and brings up message or dialog box asking for more information to be input. The output device also saves information on the disk for future use.

Processing: The CPU or central processing unit is sometimes called the Control Unit and directs the operation of the input and output devices.

he Coprocessor or the Arithmetic-Logic Unit does arithmetic and comparisons. The memory or RAM temporarily stores information (files and programs) while you are using or working on them. The BIOS or basic input/output system controls the dialogue between the various devices.