1. What is computer?
Computer is 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.
2. Hardware and 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.
3. Types of computer.
Mini and Mainframe Computers Very powerful, used by large organisations such an banks to control the entire business operation. Very expensive!
Personal Computers
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.
4.Hardware components
Input Devices --
- 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 --
- The monitor (the screen) is how the computer sends information back to you. A printer is also an output device.
5.INPUT DEVICES
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.
6.OUTPUT DEVICES
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.
7.Storage Devices
Storage Devices --
- Hard disk
drives are an internal, higher capacity drive which also stores the operating system which runs when you power on the computer.
- "Floppy"
disk drives allow you to save
work on small disks and take the data with
you.
Hard Disks
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.
8. Main part of computer.
RAM - 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 read-
only software. Often network cards and video cards also contain ROM chips.
9.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.
