Lecture 08

INTRODUCTION TO COMPUTER LECTURE 0 8

HOW A COMPUTER PROCESS DATA There are two components that handle processing in a computer. i) Central Processing Unit (CPU) ii) Memory i)

The CPU The CPU is the brain of the computer, the place where data is manipulated. In a microcomputer, the entire CPU is contained on a tiny chip called a Microprocessor. Every CPU has at least two basic parts. a) The Control Unit b) The Arithmetic and Logic Unit. a)

The Control Unit All the computers resources are managed from the control unit. Control unit works as a traffic cop, directing the flow of data. The CPU’s instructions for carrying out commands are built into the control unit. CPU Arithmetic And Logic unit

Input Devices

Control Unit

Output Devices

Memory (RAM)

Storage (Hard Disk)

1

INTRODUCTION TO COMPUTER LECTURE 0 8

b)

The Arithmetic And Logic Unit As we know that the computer can perform only two types of operations, namely arithmetic operation and logical operations. Arithmetic includes addition, subtraction, multiplication and division. Logical operations include comparison such as determining whether one number is equal to, greater than, or less than another number. Also every logical operation has an opposite e.g. in addition operation “equal to” has “not equal to”. Now when the control unit encounters an arithmetical or logical instruction, it passes that instruction to the second component of the CPU, the arithmetic and logic unit or ALU. The ALU includes a group of registers, high-speed memory locations built directly into the CPU, that are used to hold the data currently being processed. For example the control unit might load two numbers from memory into the registers in the ALU, then it might tell the ALU to divide the two numbers or to see whether the two numbers are equal.

ii)

Memory

Physically memory consists of chips either on the motherboard or on a small circuit board attached to the motherboard. This electronic memory allows the CPU to store and retrieve data very quickly. There are two types of built in memory permanent and non permanent. Some memory chips always retain the data they hold even when the computer is turned off. This type of memory is called non-volatile. Other chips in a microcomputer do lose their contents when the computer power is shut off, these chips have volatile memory. a) ROM The data in this memory cannot be changed. In fact, putting data permanently into this kind of memory is called burning in the data, and it is usually done at the factory at the time of manufacturing. The data in this chip can only be read it cannot be changed so the memory is called read only memory (ROM). ROM contains a set of instructions, which ensure that the rest of memory is functioning properly, check for hardware devices and check for an operating system on the computer’s disk drives. b) RAM The purpose of Random Access Memory (RAM) is to hold programs and data while they are in use. Physically RAM consists of some chips on a small circuit board. This memory has the capability to access each byte of data directly. This memory will be

2

INTRODUCTION TO COMPUTER LECTURE 0 8

• •

• •

available till our computer is on. If we shutdown our computer the data In this memory will be lost. RAM Technologies Many advancement in RAM technology have been made over the years. The following are the major types of RAM used in PC computers. First Page Mode (FPM) RAM FPM RAM is the oldest and least sophisticated type of RAM, Its still used in many PC’s available today. Extended Data Output (EDO) RAM EDO RAM is faster than FPM RAM and is commonly found in the fastest computers. Burst Extended Data Output (BEDO) RAM BEDO RAM is very fast RAM and is supported by a limited number of CPU’s manufactured by VIA. Synchronous Dynamic RAM (SDRAM) SDRAM delivers burst of data at very high speeds (up to 100 MHz), which provide more data to CPU at given time than older RAM technologies. SDRAM is supported by popular type of RAM on the market today.

3