What is a Computer?
An electronic device that stores, retrieves, and processes data, and can be programmed with instructions. A computer is composed of hardware and software, and can exist in a variety of sizes and configurations.
Hardware & Software
The term hardware refers to the physical components of your computer such as the system unit, mouse, keyboard, monitor etc. The software is the instructions that makes the computer work. Software is held either on your computers hard disk, CD-ROM, DVD or on a diskette (floppy disk) and is loaded (i.e. copied) from the disk into the computers RAM (Random Access Memory), as and when required.
Types of Computers
Mini and Mainframe Computers
Very powerful, used by large organisations such an banks to control the entire business operation. Very expensive!
Cheap and easy to use. Often used as stand-alone computers or in a network. May be connected to large mainframe computers within big companies.
Input Devices —
“How to tell it what to do“ – A keyboard and mouse are the standard way to interact with the computer. Other devices include joysticks and game pads used primarily for games.
Output Devices —
“How it shows you what it is doing” – The monitor (the screen) is how the computer sends information back to you. A printer is also an output device.
- The Mouse – Used to ‘drive’ Microsoft Windows
- The Keyboard – The keyboard is still the commonest way of entering information into a computer
- Tracker Balls – an alternative to the traditional mouse and often used by graphic designers
- Scanners -A scanner allows you to scan printed material and convert it into a file format that may be used within the PC
- Touch Pads – A device that lays on the desktop and responds to pressure
- Light Pens – Used to allow users to point to areas on a screen
- Joysticks – Many games require a joystick for the proper playing of the game
VDU – The computer screen is used for outputting information in an understandable format
Printers – There are many different types of printers. In large organizations laser printers are most commonly used due to the fact that they can print very fast and give a very high quality output.
Plotters – A plotter is an output device similar to a printer, but normally allows you to print larger images.
Speakers – Enhances the value of educational and presentation products.
Speech synthesisers – Gives you the ability to not only to display text on a monitor but also to read the text to you
Storage Devices — “How it saves data and programs“
Hard disk drives are an internal, higher capacity drive which also stores the operating system which runs when you power on the computer.
- Speed: Very fast! The speed of a hard disk is often quoted as “average access time” speed, measured in milliseconds. The smaller this number the faster the disk.
- Capacity: Enormous! Often 40/80 Gigabytes. A Gigabyte is equivalent to 1024 Megabytes.
- Cost: Hard disks costs are falling rapidly and normally represent the cheapest way of storing data.
- Speed: Much slower than hard disks. The original CD-ROM speciation is given a value of 1x
- speed, and later, faster CD-ROMs are quoted as a multiple of this value.
- Capacity: Around 650 Mbytes and more
- Speed: Much faster than CD-ROM drives but not as fast as hard disks.
- Capacity: Up to 17 Gbytes.
- Cost: Slightly higher than CD-ROM drives.
Main Parts of Computer
Memory — “How the processor stores and uses immediate data“
Random Access Memory The main ‘working’ memory used by the computer. When the operating system loads from disk when you first switch on the computer, it is copied into RAM. As a rough rule, a Microsoft Windows based computer will operate faster if you install more RAM. Data and programs stored in RAM are volatile (i.e. the information is lost when you switch off the computer).
ROM – Read Only Memory
Read Only Memory (ROM) as the name suggests is a special type of memory chip that holds software that can be read but not written to. A good example is the ROM-BIOS chip, which contains readonly software. Often network cards and video cards also contain ROM chips.
How Computer Memory Is Measured
- Bit – All computers work on a binary numbering system, i.e. they process data in one’s or zero’s. This 1 or 0 level of storage is called a bit.
- Byte – A byte consists of eight bits.
- Kilobyte – A kilobyte (KB) consists of 1024 bytes.
- Megabyte – A megabyte (MB) consists of 1024 kilobytes.
- Gigabyte – A gigabyte (GB) consists of 1024 megabytes.
Microprocessors — “The brain of the computer“
PCs primarily use microprocessors (sometimes called the chip). The older Intel versions include the 386, 486 and now the Pentium line. The CPU (Central Processing Unit) is normally an Intel Pentium (or equivalent) and it is one of the most important components within your computer.
- It determines how fast your computer will run and is measured by its MHz speed.
- Thus a 600 MHz Pentium is much faster than say a 400 MHz Pentium CPU.
- It is the CPU that performs all the calculations within the computer.
Some of the Factors That Impact on a Computer’s Performance
- CPU speed
- RAM size
- Hard disk speed and capacity
Operating systems software
The operating system is a special type of program that loads automatically when you start your computer. The operating system allows you to use the advanced features of a modern computer without having to learn all the details of how the hardware works. The link between the hardware and you, the user. Makes the computer easy to use without having to understand bits and bytes!
An application program is the type of program that you use once the operating system has been loaded. Examples include word-processing programs, spreadsheets and databases Software Component
Word processing applications
- Microsoft Word
- Lotus Word Pro
- Microsoft Excel
- Lotus 123
- Microsoft Access
- Lotus Approach
Software Component, Application Software
- Sage software
- Presentation tools
- Microsoft PowerPoint
- Lotus Freelance
- Desktop publishing
- Abode Photoshop
- Multimedia applications
- Microsoft’s Encarta CD-ROM based encyclopaedias
LAN – A LAN (Local Area Network) is a system whereby individual PCs are connected together within a company or organization
WAN – A WAN (Wide Area Network) as the name implies allows you to connect to other computers over a wider area (i.e. the whole world).
Uses of Network
- If ten people are working together within an office it makes sense for them all to be connected.
- In this way the office can have a single printerand all ten people can print to it.
- In a similar way other devices such as modems or scanners can be shared.
- Even more useful is the ability to share information when connected to a network.
Modem – Short for “MODulate/DEModulate”. The modem sends information from your computer across the telephone system. The modem at the other end of the phone line, converts the signal back into a format that can be used by the receiving computer.