Computer and Machine Cycle

1. C H A P T E R 1
O V E R V I E W O F C O M P U T E R S A N D L O G I C
PROG0101
FUNDAMENTALS OF
PROGRAMMING
PROG0101
FUNDAMENTALS OF PROGRAMMING
CHAPTER 1
COMPUTER AND MACHINE CYCLE

2. 2
Definition of Computer
 Computer can be define as a computer is a programmable
machine.
 A computer program is a collection of instructions that
performs a specific task when executed by a computer.
 A computer requires programs to function.
 A computer program is usually written by a computer
programmer in a programming language.

3. 3
Definition of Computer
 What computers can do?
 Office works (documents, letters, memos etc …)
 Entertainment
 Access information
 Education
 Online shopping
 Video conferencing
 Desktop publishing
 Etc …

4. 4
Definition of Computer
Computer Parts
 Computer can be divided into two parts:
 Hardware
System Unit
Input devices
Output devices
 Software
System software
Programming software
Application software

5. 5
Basic Computer Operations
Basic Computer Operations
DATA
(INPUT)
PROCESS DATA
INFORMATION
(OUTPUT)
STORE
DATA, INFORMATION & INSTRUCTION

6. 6
Basic Computer Operations
Basic Computer Operations
The computer performs four basic operations:
 Receive input data
 Process data
 Produce output information
 Store data, information and instructions.

7. 7
Machine Cycle
Machine Cycle
 Machine cycle is the basic operation cycle of a computer
processor.
 It is the process by which a computer processor retrieves a
program instruction from its memory, determines what
actions the instruction requires, and carries out those
actions.
 This cycle is repeated continuously from bootup to when
the computer is shut down.

8. 8
Machine Cycle
Machine Cycle
 There are four steps in machine cycle:
 Instruction Phase:
Fetch - get an instruction from Main Memory
Decode - translate it into computer commands
 Execution Phase
Execute - actually process the command
Store - write the result to Main Memory

9. 9
Machine Cycle
Machine Cycle

10. 10
Machine Cycle
Machine Cycle
For example, to add the numbers 5 and 6 and display the answer on the
screen requires the following steps:
1. Fetch instruction: "Get number at address 123456"
2. Decode instruction.
3. Execute: ALU finds the number. (which happens to be 5)
4. Store: The number 5 is stored in a temporary spot in Main Memory.
5 - 8 Repeat steps for another number (= 6)
9. Fetch instruction: "Add those two numbers"
10. Decode instruction.
11. Execute: ALU adds the numbers.
12. Store: The answer is stored in a temporary spot.
13. Fetch instruction: "Display answer on screen."
14. Decode instruction.
15. Execute: Display answer on screen.