CHAPTER 4Computer System
What is a Computer
A electronic devices.
That received input.
Manipulated the input (process).
Produced an output.
What is ‘Computer System’
A complete, working computer.
Includes not only the computer but also any operating system, software and peripheral devices that are necessary to make the computer function.
Cycle of Processes
There are 3 process involve in a computer:
1. Input 2. Process 3. Output
Input-Process-Output Model (IPO)
Input: Keyboard, mouse, scanner
Processing: CPU executes the computer program
Output: Monitor, printer
Storage: Hard Drive, Optical Disk, Diskettes, Magnetic Tape
Input
What is an input device?
Hardware use to enter data and instructions.
Process
Components
CPU (Central Processing Unit):
ALU (Arithmetic Logic Unit)
Control Unit
Main Memory
Output
What is an output device?
Hardware that conveys information to one or more people
Data Representation
Most computers are digital.
Recognize only two discrete states: on or off.
Use a binary system to recognize two states.
Use number system with two unique digits: 0 and 1, called bits (short for binary digits).
Byte
Eight bits grouped together as a unit.
Provides enough different combinations of 0s and 1s to represent 256 individual characters.
Numbers
Uppercase and lowercase letters
Punctuation marks
Other
Three popular coding systems to represent data:
ASCII - American Standard Code for Information Interchange.
EBCDIC - Extended Binary Coded Decimal Interchange Code.
Unicode - coding scheme capable of representing all world’s languages.
ASCII used total of 7 bits to represent character (letters, numbers and punctuation marks).
7 bits – encoding total of 128 character (27 = 128).
EBCDIC used total of 8 bits to represent character (letters, numbers and punctuation marks).
8 bits – encoding total of 256 character (28 = 256).
EBCDIC primarily used on mainframe computer and high end servers.
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