4.1 Types of Software and Interrupts

Question 1

What is system software?

Answer 1

The programs that allow hardware to run properly and allow the user to communicate with the computer

Question 2

What is application software?

Answer 2

The programs that allow the user to perform a specific task

Question 3

State 3 features of system software

Answer 3

Set of programs to control and manage the operation of computer hardware
Provides a platform on which other software can run
Required to allow hardware and software to run without problems
Provides a human computer interface (HCI)
Controls the allocation and usage of hardware resources.

Question 4

State 3 features of Application software

Answer 4

Used to perform various applications (apps) on a computer
Allows a user to perform specific tasks using the computer’s resources
May be a single program (e.g. NotePad) or a suite of programs (e.g. Microsoft Office)
User can execute the software as and when they require.

Question 5

State 3 examples of application software and their use

Answer 5

Word Processor- Used to manipulate a text document, such as an essay or a report
Database - Used to organise, manipulate and analyse data. Typically made up of one or more tables.
Control and measuring- Used to allow a microprocessor to interface with sensors to measure and control processes
Spreadsheet - Used to organise and manipulate numerical data (in the form of integer, real, date …).
Video Editing - Used to manipulate moving images with titles, colour correction, altering sound etc…
Photo Editing Graphics Manipulation
Graphics Manipulation - Used to edit, create and manipulate bitmap and vector images.

Question 6

State 3 examples of system software and their use

Answer 6

Compilers - A program that translates a program written in a high-level language (HLL) into machine code
Linkers - A program that takes one or more object file produced by a compiler and combines them into a single program
Device Drivers - Software that enables one or more hardware devices to communicate with the computer’s operating system.
Operating Systems - Software running in the background of a computer system which manages many of the basic functions.
Utilities - Software that are designed to carry out specific tasks on a computer e.g. anti-virus

Question 7

State 2 types of utility software

Answer 7

Back up
Security
Anti-Virus
File Compression e.g. Winzip
Defragmentation
Screensavers

Question 8

What is utility software

Answer 8

A specific category of System software that support a computer system in operating as safely and efficiently as possible.

Question 9

Describe Back Up software (Utility)

Answer 9

It schedules creating copies of files when changes have been made to them.
Multiple versions means you can restore deleted or corrupted files.
For total security there should be three versions of a file:
* the current (working) version
* a locally backed up copy of the file
* a remote back-up version stored well away from the computer

Question 10

Describe Defragmentation software (Utility)

Answer 10

As a HDD becomes full, blocks used for files will become scattered all over the disk surface (in potentially different sectors and tracks as well as different surfaces).
Defragmentation software oves part of files around so all parts are stored together.
Free memory space is collected together to reduce HDD head movements

Question 11

Describe security software (Utility)

Answer 11

Manages access control and user accounts
Oversees the updating of software.
Also links into links into other utility software, such as virus checkers and firewalls

Question 12

State 5 functions of an operating system

Answer 12

• Provides a user interface for applications
• Opens, closes and installs software
• Manages the hardware and peripherals
• Manages memory e.g. loading programs into RAM
• Manages processor time allocation
• Manages interrupts and error handling
• Manages file handling e.g. organising, saving and deleting
• Manages security e.g. logging on and passwords
• Manages user accounts

Question 13

Why do we need an Operating System?

Answer 13

• Allows a user to communicate with the computer using hardware
• Provides the user with a user interface for interaction with the computer
• Allows for multitasking and handles interrupts

Question 14

What is Virtual Memory

Answer 14

• When RAM is full a section of the hard disk is used to allow more programs to be loaded.
• It is much slower than RAM.

Question 15

What is a device driver?

Answer 15

• A piece of software that allows peripheral devices to communicate with the OS
• Translates signals to/from peripherals to something the OS can understand

Question 16

What is spooling?

Answer 16

• Simultaneous Peripheral Operations On-Line
• Data are temporarily held in a buffer waiting for an output device to access it e.g. printer

Question 17

What is memory management?

Answer 17

Operating system assigns blocks of memory to programs running in a computer

Question 18

What is scheduling?

Answer 18

Operating system determines the order in which the programs should use the CPU and how much time is allocated to each one

Question 19

What is polling?

Answer 19

• Operating system regularly checks each peripheral device in turn to discover whether it needs the attention of the operating system.
• Less efficient CPU use than interrupts

Question 20

What is a buffer

Answer 20

Temporary memory which stores data until it is ready to be used.

Question 21

What is an interrupt?

Answer 21

Interrupts are signals sent to the CPU or operating system
They can be sent from hardware (e.g. printer - run out of paper) or software (e.g. email client, email arrived)
The signal is used to request processor time
Interrupts can have different priorities e.g. high/low
It enables multitasking to be carried out on a computer

Question 22

Explain how an interrupt is generated and handled when a key is pressed on a keyboard

Answer 22

• A key is pressed that presses a switch
• The key press completes a circuit
• The location of the keypress is calculated
• The location of the keypress is used to look up the binary ASCII value
• The binary ASCII value is then sent to a buffer to wait to be processed
• An interrupt is then sent to the processor to let it know there has been a key press
• The binary ASCII value is then processed by the CPU
• The CPU then returns to the previous process.

Question 23

What is multitasking?

Answer 23

When multiple tasks share the processor

Question 24

What is multiprogramming?

Answer 24

Running more than one program at a time

Question 25

State 2 types of HCI (Human Computer Interface)

Answer 25

GUI (Graphical User Interface)
CLI (Command Line Interface)

Question 26

What is a GUI?

Answer 26

Graphical User Interface
The user communicates with the operating system using windows, drop-down menus, icons and pointers (WIMP).

Question 27

What is a CLI?

Answer 27

Command Line Interface
The user communicates with the operating system by typing commands

Question 28

What are the advantages and disadvantages of a GUI?

Answer 28

A: Easy to use, especially for a beginner
A: You do not have to learn complicated commands

D: GUIs take up a much larger amount of hard disk space
D: They need significantly more memory (RAM) to run
D: They use more processing power than other types of interface

Question 29

What are the advantages and disadvantages of a CLI?

Answer 29

A: Can be much faster if the user knows the commands
A: Needs much less memory (RAM)
A: Does not use as much CPU processing time

D: it can be very confusing and slow for novices
D: Commands have to be typed precisely.
D: Large number of commands which need to be learned

Question 30

Describe how an interrupt works

Answer 30

A signal is sent to the CPU or operating system to request processor time
…. may be from a device or software
The processor stops to service/deal with the interrupt
Once the interrupt is serviced the previous process continues

Question 31

Describe how an Interrupt Service Routine works

Answer 31

• Whenever an interrupt is received it needs to be serviced.
• The status of the current task being run is saved so the contents of the Program Counter (PC) and other registers are saved.
• Then the interrupt service routine (ISR) is executed by loading the start address into the Program Counter (PC).
• Once the interrupt has been fully serviced, the status of the interrupted task is reinstated
• The contents of all the saved registers are then retrieved) and the process continues.

Question 32

What is the BIOS?

Answer 32

Basic Input Output System
Stores the boot up instructions
Handles the start up of a computers motherboard.
It tells the computer where the OS is located and loads and executes the needed parts of the OS.
Often referred to as firmware.

Question 33

What is an Interrupt Service Routine?

Answer 33

Software that handle requests for CPU time (for example, when the printer is out of paper) and it sends a request to the CPU for processing

Question 34

What is firmware?

Answer 34

A program that provides low level control for devices

Question 35

Give some examples of how an operating system performs security mannagement

Answer 35

• By carrying out operating system updates as and when they become available
• By ensuring that anti-virus software (and other security software) is always up to date
• By communicating with, for example, a firewall to check all traffic to and from the computer
• By setting up user accounts and making use of passwords and user IDs); this helps to ensure the privacy of data
• By maintaining access rights for all users
• By offering the ability for the recovery of data (and system restore) when it has been lost or corrupted

Question 36

Give some examples of how an operating system manages periperals/hardware?

Answer 36

• communicates with all input and output devices using device drivers
• uses a device driver to take data from a file (defined by the operating system) and translates it into a format that the input/output device can understand
• ensures each hardware resource has a priority so that they can be used and released as required
• manages input/output devices by controlling queues and buffers;

Question 37

Why