Components of computer system

Computer Systems are made up of many different parts, for example, hardware, software, processor, memory etc. It is important that you have a basic understanding of some of the main parts of a computer.

Hardware is any physical component of the computer that you can touch, see and pickup.
Examples of hardware include monitor, keyboard, mouse, disk drives, printer, scanner and speakers, etc.

Software is the applications and programming instructions needed to make the computer hardware do useful work.

There are two types of software:

• System Software
• Application software

System software:- These are the software essential for the system to work.
Eg: Operating system, drivers, utilities, compilers, etc.

Application software: These are software required for the user to do some useful tasks.
Eg: Photoshop, Flash, MS Word, Media player, Games, etc.

Operating System
An operating system is system software that manages all the resources of a computer.
Example for the operating system are:

• Windows
• Linux
• Mac
• Solaris

The two main interfaces provided by operating systems are:

GUI – Graphical User Interface
Command-line interface
(Interface defines the way the user is going to interact with the hardware.)

A GUI operating system contains windows, icons menus, pointers (WIMP) for the user to interact with the computer. GUI operating systems are user very friendly.
Windows, Linux, Mac are examples for GUI operating system.

In a command-line interface to do any task, the user has to type commands in correct syntax. So it is usually used by computer experts.
DOS and UNIX are examples foe command line operating system

A peripheral is any device which connects to the computer and exchanges data with the CPU. Peripherals include all of the computer's input and output devices.

Monitor, keyboard, mouse, printer, scanner, speakers, external hard drives, etc.

Components of CPU
You need to have a basic understanding of the three main parts of a CPU.
They are:

1. Control Unit
2. Immediate Access Store
3. Arithmetic and Logic Unit (ALU)

1. The Control Unit
Control Unit has three main jobs:
• It controls and monitors the hardware attached to the system to make sure that the commands given to it by the application software are executed.

• It controls the input and output of data so that the signals go to the right place at the right time

• It controls the flow of data within the CPU

2. The Immediate Access Store
This holds the data and programs needed at that instant by the Control Unit.
The CPU reads data and programs kept on the backing storage and stores them temporarily in the IAS's memory.
The CPU needs to do this because Backing Storage (e.g. the hard disk) is much to slow to be able to run the applications from it directly.

3. Arithmetic and Logic Unit
This is where the computer processes data either by manipulating it or acting upon it. It consists of two parts:

Arithmetic part - which does exactly what you think it, should be doing - it performs the calculations on the data e.g. 3 + 2 = 5
Logic part: This deals with logic and comparisons. For example, it works out if one value is greater, less than or equal to another.

The Motherboard is the central circuit board of your computer. All of the components and peripherals plug into it.

The motherboard houses the ROM chip, which stores the BIOS instructions, RAM chips, CPU, graphics card, sound card, network interface card, hard disk and various other external ports and peripherals all attach directly to it.

The job of the motherboard is to relay information between the components and peripherals.

Disk Drives
The purpose of a disk drive is to read data from a storage device. Common disk drives that you will come across in your studies are:

• Hard disk drive
• Removable hard disk drive
• Floppy disk drive
• zip disk drive
• CD drive
• DVD drive

The hard disk drive is installed inside your computer and it reads data stored on the hard disk.

The two main types of memory that you need to clearly understand are
Random Access Memory (RAM) and Read-Only Memory (ROM)

Read-Only Memory (ROM)
Data stored on ROM is not erased when the power is switched off - it is permanent. So ROM is called as 'non-volatile memory'.

The ROM chip is used to hold instructions that tell the computer how to load the operating system. This data is inscribed at the time of manufacturing the computer.

Random Access Memory (RAM)
RAM is used for holding data and programs which are currently running on the computer. RAM is also called a primary memory of the computer.
In contrast to ROM, RAM is volatile memory. The data is held on a chip, but only temporarily. The data disappears if the power is switched off. Have you ever forgotten to save your work before the computer crashed? When you log back on, your work has disappeared. This is because it was stored in RAM and was erased when the PC was switched off.

However, if you had saved your work, it would have been transferred from RAM to the hard disk where it would have been stored safely.

Cache Memory
Most data is stored on the hard disk. When we use that data, it is loaded into RAM because it is much faster to access the data from RAM than from the hard disk.
When we looked at the 'immediate access store' earlier, we found out that the CPU needs to access data very quickly. Although RAM is faster than the hard disk, it still isn't fast enough to cope with the speed that the CPU needs to deal with data.

The cache is a special type of computer memory which can be accessed much faster than RAM. The CPU looks first in the cache for the data it needs. If the data is there, it will retrieve it and process it. If the data is not there, then the CPU accesses the system memory and then puts a copy of the new data in the cache before processing it.

Cache memory is volatile i.e. when the computer is shut down; the data stored there is lost.

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