Cureent Affairs BCS Bises Sonka. pdf

Lesson 3 : How the System Works 

3.1. Learning Objectives
On completion of this lesson you will be able to describe:
 What is system software
 An overview of the booting process
 Different types of boot (cold & warm).

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3.2. System Software 

System software is the program that controls different devices in the microcomputer. System software has the following components: 

 Monitor program or BIOS: The program used to control the basic functions of different devices. 

 Operating system: The software responsible for allocating system resources, including memory, processor times, disk space, and peripheral devices such as printers, modems, and the monitor. 

3.3. An Overview of the Booting Process 

Booting means loading operating system in the memory by the PC itself. Basically, a PC does three things when it boots. 

 First, the hardware must work. 

 Second, the processor starts up and runs a program in the BIOS called the ‘Power on Self Test.’ 

 Third, BIOS loads the operating system on the active partition. 

Then, assuming that the basic hardware can function, you'll recall that each PC has a set of software built into a ROM, called the Basic Input Output System, or BIOS. That BIOS is a collection of important programs, programs to control the video board, the disk controller, the keyboard, and the system clock, just to name a few, but perhaps the most important of those programs that starts up the PC. That program determines what hardware is in the system, does a basic checkout of that hardware, and senses the presence of BIOS-like programs associated with expansion boards in the PC. If those programs exist on the expansion boards, the BIOS will yield control to them so that they can do the initialization. Once the BIOS startup and checks work out all right, the BIOS then attempts to load the system software from the floppy or hard disk. Once the operating system gets loaded from disk into the computer's RAM, the BIOS passes control to the operating system, and the computer is ready to use.