CHAPTER 2

COMPUTERSYSTEM

COMPUTER SYSTEM

A computer system is defined as combination of components designed to process data and store files. A computer system consists of four major hardware components; input devices, output devices, processor and storage devices. A computer system requires hardware, software and a user to fully function.

input

•Input is any data or instructions that we enter into the computer system for processing. There are four types of input: which are text, graphic, audio and video. Example of input devices are keyboard, light pen, joystick, microphone, mouse, video & digital camera.

process

•The processing unit controls all activities within the system. The CPU is an example of a processor. It has the same important as the brain to human being.

Storage

•Storage is a location which data, instruction and information are held for future use. It is the physical material that keeps keeps data, instruction and information. There are two types of storage. They are the primary storage and secondary storage. The example of storage devices are hardisk, Floppy Disk, diskette, RAM, CD ROM and DVD ROM.

output

•Output is data that has been processed into a useful form, called information. There are four types of output, which are texts, graphics, audio and video. Example of output devices are monitor, printer, speaker and plotter.

Describe the information processing cycle which includes input, process, output and storage.

input

•Users input data or instruction into the computer system to be process. Input could be either text, graphic, audio or video. Input devices are used by users to input data. Input devices are any electronic device connected to a computer and produces input signals.

process

•Data or instruction being input into the computer system is then processed by the CPU which controls all activities within the system. The results of the processed data are then sent to an output device as usable data.

•A CPU interprets the and carries out the instructions by processing data and controlling the rest of the computer’s components.

•A CPU consists of two subcomponents; the Control Unit (CU) and the Arithmetic Logic Unit (ALU). CU’s main function is to direct the CPU to process data by extracting instructions from memory and decodes and executes them. The CU manages a four-step basic operation which is called a machine cycle. The steps are Fetching, Decoding, Executing & Storing

storage

•Computer storage is important to help users store programs and data to be used at a later time.

•It is also useful to keep current data while being processed by the processor until the information is saved in a storage media such as a hard disk or a diskette. Computer storage also stores instructions from a computer program. There are two type of computer storage; primary storage and secondary storage.

Data Representation

Binary digit

Bit

Byte Character

Character codes

BINARY DIGIT

  Computers recognize only two discrete states: on and off. These states can be represented by two

digits, 0 and 1. Each 0 or 1 is called a bit in the binary system.

Bit is the smallest unit of data a computer can process. Bit is a short for binary digit. The binary system has a base of 2 with the two digits (0 and 1). Combinations of 0s and 1s represent larger numbers.

  BIT  A bit is the smallest unit of data that the computer can process. Bit is a short for binary digit. A bit

is represented by the numbers 1 and 0. These numbers represent the binary system. They correspond to the states of on and off, true and false, or yes and no.

All digital data use the binary system to process the information. This information include letters, digits or special character.

 BYTE  Byte is a unit of information built from bits. One byte is equals to 8 bits. Eight bits that are

grouped together as a unit. A byte provides enough different combinations of 0s and 1s to represent 256 individual characters.

One byte represents a single character such as the number 3, letter b or a $ symbol. Bits and bytes are the basis for representing all meaningful information and programs on computers.

 

CHARACTER  8 bits = 1 byte  One byte represents one character such as A, 7, 9 and +.Eight bits that are grouped

together as a unit. A byte provides enough different combinations of 0s and 1s to represent 256 individual characters.

For example, the capital letter F is represented by the binary code 01000110 that can be understood by the computer system. Eight bits grouped together as a unit are called a byte. A byte represents a single character in the computer.

   CHARACTER CODES  There are three character codes to represent characters which are ASCII, EBCDIC and

Unicode. Each byte contains eight bits. A byte provides enough different combination of 0s and 1s to represent 256 characters.

The combinations of 0s and 1s are defined by patterns. These patterns are called coding scheme. The 256-character capability of ASCII and EBCDIC is too small to handle the characters that are used by other languages such as Arabic, Japanese and Chinese. 

The Unicode coding scheme is designed to solve this problem. It uses two bytes (16 bits) to represent one character. Unicode will have more than 65,000 different characters. This can cover all the world’s languages.

ASCII code

ASCII pronounced as "ask-key" stands for the American Standard Code for Information Interchange and was proposed by ASA (American Standard Association) in 963 and was finalised in 1968.ASCII is a standard of 7-bit code used to represent characters, which include letters, numbers and punctuation marks.

7 bits allow the computer to encode a total of 128 characters for the numbers 0-9, uppercase and lowercase letters A-Z and a few punctuation symbols. However this 128 bit code only suitable for english language speaking users.

IBM and Apple expanded the amount of space reserved for the character codes to 8-bits, equivalent to 1 byte.

Functions of ASCII codes

ASCII was established to achieve compatibility

between various types of data processing equipment making it possible for the

components to communicate with each

other successfully.

ASCII enables manufacturers to produce

components that are assured to operate

correctly in a computer.

ASCII makes it possible for humans to interact with a computer. It also enables

users to purchase components that are compatible with their

computer configurations

How ASCII Codes works in computer system

When you press a key, for example the letter D on your

keyboard, the electronic signal is sent to the CPU for the computer to process and

store in memory.

Every character is converted to its corresponding binary

form.

The computer the processes the letter as a byte., which actually a series of on and off of

electrical states.

When the computer is finished processing the

byte, the software installed in the system convert the byte back

which is then displayed in the screen.

In this example, the letter D is converted to

01000100.

Input Device• You can enter data by pressing the keys on

the keyboardText• A digital camera allows you to take pictures

and store the photographed images digitallyGraphic • Input the speech, music and sound effects

entered into the computerAudio • Input of motion images captured into the

computer by special input devices.Video

Components of

motherboard

Central Processing Unit

(CPU)

Expansion Slot

Expansion CardsRAM Slot

Ports and Connectors

Information and document are stored in computer storage so

that it can be retrieved whenever they are needed later

on.

Computer storage is the holding of data in an electromagnetic form for access by a computer

processor.

Storage

Stores instructions from a computer programs

Help users store programs and data to be used at a later time

Function of Computer Storage

Definition of operating system Set of programs that schedule tasks,

allowcates storage and presents a default interface to the user between applications.

Function of the operating system are : Starting a computer Providing a user interface Managing data and programs Managing memory Configuring devices

End chapter 2…….