XI Information Technology - BIEK Chapter 4 - Micro Computers

Micro Computers
Introduction
Computers are the electronic devices that can follow instructions to accept input process that input and produce information. From capability point of view there are four types of computers as mentioned in the previous chapter.

1. Micro Computers

2. Mini Computers

3. Mainframe Computers

4. Super Computers


1. Micro Computers

The most widely used and fastest growing type of computer is the micro computer. There are two categories of micro computers desktop and portable. Desktop computers are small enough to fit along the side of a desk and yet are too big to carry around. Personal computer are the type of desktop. Portable computers are the micro computers that are small enough and light enough to move from one place to another. There are four categories of portable computers.

i. Laptops

ii. Notebooks

iii. Sub notebooks

iv. Personal Digital Assistants.




Components of Computer
The computer itself the hardware has many parts but each fall into one of four categories.

1. Processor

2. Memory

3. Input and Output Devices

4. Storage Devices.

Only first two categories will be discussed in this chapter, whereas next two categories will be studied in the subsequent chapter.




The CPU or Processor
The part of the computer that runs the program (executes processor) is known as the processor or central processing unit. The processor is like the brain of the computer the part that organizes and carries out the instructions that come from either user or software. The central processing unit has two components the control unit and the arithmetic logic unit.




Control Unit
The Control unit tells the rest of the computer system how to carry out a program's instruction. It directs the movement of the electronic signals between teh memory which temporarily holds data, instruction and processed information and the arithmetic logic unit. It also direct the signal between the CPU and the input and output devices.


Arithmetic-logic Unit
The arithmetic logic unit usually called ALU performs two types of operations arithmetic and logical. The arithmetic operations are the fundamental math operations addition, substraction, multiplication and division. Logical operations consists of comparisons. i.e. two pieces of data are compared to see whether one is equal to (=), less than (<) or greater than (>) the other.




Memory (RAM)
Computer has two types of memory random access memory (RAM) and read only memory. (ROM) In this chapter only RAM will be studied whereas ROM will be studied later. RAM also known as primary memory internal memory or main memory hold.

Data for processing
Instruction for processing the data that is the program
Information that is processed data waiting to be output and sent to secondary storage such as floppy disk in a disk drive.
One of the most important fact to know about memory is that part of its content is held only temporarily. In other words, it is stored only as long as computer is turned on. When the machine is turned off the contents immediately vanish.

The next important facts of know about memory is that its capacity varies in different computers.