Lesson Notes By Weeks and Term - Senior Secondary School 1

TERM: 2^nd Term

WEEK: 1

CLASS: S.S. 1

DATE:

SUBJECT: Computer Science
TOPIC: Computer system software

Understanding Computer System Software

This is in contrast to hardware; it is the invisible part of a computer system. These set of software are provided by the manufacturer to assist the computer operators/users to make the best use of their machine as distinct from the specific programs written to solve specific problems.

Software is generally categorised into two:

• System software
• Application software

1. System software: This software contributes to the control and performance of the computer system. The collective name of the programs is system software or utility software. System software can further be sub-divided into – a. operating system, b. translators, c. utilities. System software is a type of computer program that is designed to run a computer’s hardware and application programs. If we think of the computer system as a layered model, the system software is the interface between the hardware and user applications.The operating system (OS) is the best-known example of system software. The OS manages all the other programs in a computer.Other examples of system software and what each does:
   • The BIOS (basic input/output system) gets the computer system started after you turn it on and manages the data flow between the operating system and attached devices such as the hard disk, video adapter, keyboard, mouse, and printer.
   • The boot program loads the operating system into the computer’s main memory or random access memory (RAM).
   • An assembler takes basic computer instructions and converts them into a pattern of bits that the computer’s processor can use to perform its basic operations.
   • A device driver controls a particular type of device that is attached to your computer, such as a keyboard or a mouse. The driver program converts the more general input/output instructions of the operating system to messages that the device type can understand.
   • According to some definitions, system software also includes system utilities, such as the disk defragmenter and System Restore, and development tools such as compilersand debuggers.

• Operating system: A computer cannot understand instructions without the operating system. OS is a set of instruction (programs) designed to efficiently manage the resources of the computer system. Operating system supervises the input and output operation, communicating with the operator and allocating the computer resources to allow the operation of the computer to progress smoothly with minimum intervention.

An operating system performs these services for applications:

• In a multitasking operating system where multiple programs can be running at the same time, the operating system determines which applications should run in what order and how much time should be allowed for each application before giving another application a turn.
• It manages the sharing of internal memory among multiple applications.
• It handles input and output to and from attached hardware devices, such as hard disks, printers, and dial-up ports.
• It sends messages to each application or interactive user (or to a system operator) about the status of operation and any errors that may have occurred.
• It can offload the management of what are called batch jobs (for example, printing) so that the initiating application is freed from this work.
• On computers that can provide parallel processing, an operating system can manage how to divide the program so that it runs on more than one processor at a time.

Examples of Operating System

• Ms DOS: Microsoft Disk operating system commonly
• Noval: This is usually used in a network environment and linked together to share resources.
• UNDC: Usually used in a multiuser environment where many people can use one log computer at the same time.
• Windows Operating System: Can be defined in a single microcomputer or in a network environment.

Functions of the Operating System

All operating systems must be the same and can be divided into 3:

Allocating system resources: Operating system directs the traffic (movement) inside the computer deciding what resources will be used and for how long.

• Time: The CPU time is divided into time slices which are measured in milliseconds. When a task starts, a certain number of time slices is assigned. When the time expires, another task gets the turn to start; the first task must wait until it has another turn. Tasks are assigned so that the high priority task gets more time slices than the low priority task.
• Memory: The memory must be managed at all times. One way to help the traffic arm is to use virtual memory, which includes disk space as main memory. It is slower to put data on hard disk but it increases the amount of time. When the memory gets full, some of the data is paged out to the hard disk. This is called swapping.
• Input and output flow control: The OS reads data that are coming in data form from the disk and signals the printer to print and send data. To speed up the output to the printer, most OS allows print spading, where the data to be printed is first put in file, this helps to sped up the process.

Breakdown of Operating System Functions.

1. Boot process: When the computer is switched on the boot program that is resided in Rom initialize the setup of the computer, the then load the rest of the operating system from the banking storage (hard ware) in the RAM.
2. Operating system does the work of sharing and accounting of the computer resources
3. Operating system handles the input and output of data and information.
4. Operating system handles the management of memory.
5. Operating system handles the management of the hardware.
6. Operating system handles multitasking and multi programming.
7. Operating system handles protection and error trending.
8. Operating system acts as an interface between the user and the computer
9. Operating system controls interaction and program control

 ASSESSMENT

1.  Computer system software is the ___ part of the computer
   (a) visible
   (b) invisible
   (c) hard
   (d) soft
2. Software contributes to the ____ and ____ of the computer system
   (a) hard and soft
   (b) clean and unclean
   (c) straight and crooked
   (d) control and performance
3. The set of instructions designed to efficiently manage the resources of the computer system is known as
   (a) conducting system
   (b) producing system
   (c) software system
   (d) operating system
4. Examples of operating systems are the following except
   (a) MS DOS
   (b) Noval
   (c) Doors
   (d) Windows
5. RAM means
   (a) Routing Access Memory
   (b) Return Access Memory
   (c) Round Access Memory
   (d) Random Access Memory

ANSWERS

1. b
2. d
3. d
4. c
5. d