Applications generation

Question 1

what is systems software

Answer 1

needed by the system to control hardware and run applications

Question 2

what is the purpose of the operating system?

Answer 2

provide a user interface
handle memory management
interrupt handling
processor schedhuling to provide ‘multi-tasking’

Question 3

what are utility programs?

Answer 3

utliyty programs optimise the performance of teh computer and peform useful background tasks
disk defragmenter
automatic backup
automatic updating
virus checker
compression software

Question 4

what is the disk defragmenter

Answer 4

large files stored on a magnetic hard drive may be split across severeal pyhsical disk locations
the defragmenter reoragnises teh hard drive so that the files are in sequential blocks where possible

Question 5

what is an automatic backup?

Answer 5

data in permanent storage needs to be regularly backed up

Question 6

what is automatic updating?

Answer 6

runs in the background detecting software update releases and automatically installing them
some add new software features
fix security issues(which could be exploited by hackers)

Question 7

what is virus checker?

Answer 7

scans permanent storage for viruses by comparing files known to virus definitions
may scan files ‘on access’ as they are opened
may be kept up to date with new viruses definitions

Question 8

what is compression software?

Answer 8

Compression software can reduce the size of the files

we may want to send files across the internet

Question 9

what is application software?

Answer 9

software that performs a task to benefit the user

Question 10

what is off the shelf software?

Answer 10

ready-made software available to anyone to use

Question 11

what is bespoke software?

Answer 11

software that is custom written for a specific user

bespoke software is mostly used by business rather than individuals

Question 12

what is open source software?

Answer 12

allows anyone to access its source code
open sourced licensed but free to use
anyone may modify and sell it(the condition the software is also open source)

Question 13

what is closed software(proprietary)?

Answer 13

does not allow access to its source code
must pay the owner of the copyright for the licence to use the software
may be restrictions on how the software is to be used

Question 14

Off the shelf software VS Bespoke software

Answer 14

Off the shelf software :
Less expensive since the cost is shared among all the other people buying the package
Bespoke software:
More costly and requires expertise to analyse document requirements

Question 15

Advantages and disadvantages of open source and closed source

Answer 15

Open source is free-Users are free to amend the source code of open software
Open source software has the advantage that anyone can help find security holes in it but this also includes those who may exploit such failures maliciously before they are fixed

Question 16

what is a translator?

Answer 16

Computers follwo insturctiosn that comprimise of opcode and an operand.We call this machine code.While computers only understand machine code,humans write programs in much easier to read programming languages.In order to convert these programming languages to machine code.computers can use translator programs

Question 17

What are assemblers and assembly code?

Answer 17

Machine code, being made up of just 1s and 0s is very diffcult for humans to follow.To get round this,coputer scientists started to use assembly code.In assembly code the opcode is represented by a mnemonic and teh operand is represented in denary or hexidecemal.A program called an assembler is then used to convert each line of assembly code into machine code

Question 18

Define interpreter

Answer 18

A translator program that reads and executes a program line by line

Question 19

Define compiler

Answer 19

A translator program converts high-level soure code into an exutable machine code file

Question 20

what happens in Lexcial analysis

Answer 20

Comments and whitespace is removed from the program
the remaining code is turned into a series of tokens
a symbol is created to keep track of variables and subroutines

Question 21

What is syntax analysis?

and what happens druing it?

Answer 21

An abstract syntax tree is built from the tokens produced during lexical analysis
If any tokens break the rules of the language, syntax errors are general
diagnostics may be given
accepts output form lexical analysis

Question 22

what is a linker?

Answer 22

A linker is used to combine compiled code with that from a library into a single executable file

Question 23

What is a loader?

Answer 23

A loader is part of th eoperating system and is reposbile for loading a program into memory

Question 24

Define a Library

Answer 24

A pre-written collection of code that allows programmers to import functionality into their own programs

Question 25

What are libraries

Answer 25

Often code to perform complex tasks has already been written and package as a library.This code can be reused by another programmer

Question 26

Advantages of libraries?

Answer 26

They save time, rather than rewriting code someone else has written
They can cover complex areas that require expertise in an area and would be tie consuming to code
A library coded in one language can be used in programs written in another language