Thursday, March 02, 2006

SD work


1. Explain the functions of the operating system. Give examples of some operating systems in use today.

An operating system usually provides the link between the application program and i/o devices.
Its main tasks are in the management of resources and to isolate the user from the direct use of hardware items.


Custom software is specifically designed to meet a need that off the shelf software will not meet.

Dedicated software is purchased by the user to complete a specialised taks.

Custom software: Adobe Photoshop
Application software: Oasis
System software: Macintosh


The user wishes to perform an application task. When switched on, the computer runs a bootstrap program stored in ROM which automatically loads the operating system, stored on the disk drive, into RAM. This then allows selective access to the application programs, also stored on the disk drive. Once selected, the application programs is loaded into RAM and begins running. The user is then able to perform the task required. The instructions from the from the application programs work together with the instructions in the operating system to allow appropriate application input, processing of the data and production of the required outpot. When the user has finished the task, the application program is removed from the RAM.


a) The function of a bus is to carry electronic signals between cpu and other system devices
b)Ram-cpu-rom uses bus, outside hardware-inside is cable.


b) Cable connects externally, and bus is internal.


A buffer is temp stoarge.


Microprocessor chip and memory chip.


A peripheral is an external device attached via cable


The purpose of any computer system is to input data, process it, and output it.


System software controls the hardware of a computer system.


The bootstrap program is in ROM


When you start your computer you must turn on the power. Modern computers are electrical machines. They have a electrical power supple which moderates the normal electrical current and voltage to make them the correct values to be used in all the parts of the computer. All of the hardware devices which make up a modern computer use electrical power. If their electricity power supply fails no computer can operate for very long.

Exercise 2.11

1/ Hardware foolows the instructions provided by software. The CPU moves through the steps of the fetch-execute cycle as it executes the instructions one by one, The first stage in the fetch execute cycle is for the central processing unti to fetch the the instruction.This step is followed by the process of decode, where the central processing unti works out what to do. The last two steps are called the execute-store cycle. This cycle begins with the cpu carrying out the instructions, following which the central processing unit sends the result to primary storage.


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