Types and Components of Computer Systems

Topics: Computer, Application software, Computer software Pages: 6 (1355 words) Published: September 9, 2013

Types and components of computer systems
Memory There are two types of memory: • RAM (random access memory) • ROM (read only memory). Random access memory RAM is the computer’s ‘working memory’. RAM temporarily stores programs and data that are being used at a given time. The contents of RAM can be changed and are lost when the computer is turned off. This is known as ‘volatile memory’. Read only memory The main use of ROM is to store the program that runs when the computer is turned on which loads the operating system. The contents of ROM can’t be changed and aren’t lost when the computer is switched off. This is known as ‘non-volatile memory’. Bits and bytes Computers store and process data using binary numbers. A single unit in binary is called a bit which stands for binary digit. Computer memory is measured in bytes. One byte is made up of eight bits. 1 0 0 0 0 0 1 0

The eight-bit binary code in this byte represents the letter B. The size of a computer’s memory is normally measured in kilobytes (kB), megabytes (MB) or gigabytes (GB). The table below shows some of the main units of size that we use to measure computer memory.

Unit kilobyte megabyte gigabyte terabyte

Abbreviation kB MB GB TB

Size 1 kB = 1024 bytes 1 MB = 1024 kB 1 GB = 1024 MB 1 TB = 1024 GB

IGCSE ICT © Cambridge University Press 2010

Revision notes: Module 1 1

Main components
Hardware – all the parts of the physical equipment which makes the computer. Software – all the programs that allow the hardware to carry out the data processing.


Central processing unit (CPU)

Backing store


Why use computers? • Computers are extremely fast. • Computers are very accurate. • Computers can work 24 hours per day, 365 days per year. • Computers make some jobs possible. Disadvantages of using computers • Computers can replace people’s jobs. • Computers hold personal information which could be misused. • Computers can fail and without them the job may not get done. Processing data Computers can: • calculate • sort • search • store • draw.

IGCSE ICT © Cambridge University Press 2010

Revision notes: Module 1 2

Operating systems
An operating system (OS) is a set of programs that controls how the hardware and applications of a computer works. An OS is the way of communicating between the user and the computer. The OS loads and runs the other software application programs and other jobs. The operating system on a computer means that usually only certain applications will run on that computer.

Functions The operating system: • enables communication between the user and the computer; • loads and runs applications programs as well as other jobs; • will only run applications written for that particular type of OS; • handles input and output: – taking data from the input devices and sending it to RAM; – taking output and sending it to the correct output device; • handles the transfer of data from memory to and from the backing storage devices; • allocates memory space to programs and data; • loads and runs the applications software in memory; • handles any errors while the software is running; • manages system security, with user ID and passwords; • provides a human–computer interface, or HCI, for the user. Human–computer interface (HCI) This is the method by which the users communicates with the computer, sometimes called the user interface. Two type of HCI are: • command-line interface • graphical user interface or GUI. Command-line interface The user types in the instructions using command words.

The main advantage of command-driven interfaces is that, providing the user knows the commands, they can be quick to carry out, since they require less translation by the OS than GUIs. They can also be used in batch files to carry out repetitive administration tasks that would take a long time using a GUI. Graphical user interface The most widely used type of graphical user interfaces are WIMP (Windows...
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