1.2.2 - Applications Generation

Question 1

What is applications software?

Answer 1

Applications software is designed to be used by the end-user to perform one specific task.
Application software requires systems software in order to run.

Question 2

What is systems software?

Answer 2

Systems software is low-level software that is responsible for running the computer system
smoothly, interacting with hardware and generally providing a platform for applications
software to run.
The user does not directly interact with systems software but it ensures
high performance for the user.

Question 3

What are utilities?

Answer 3

Utilities are a key piece of system software integral to ensuring the consistent, high
performance of the operating system.
Each utility program has a specific function linked to
the maintenance of the operating system.

Question 4

What is the compression utility?

Answer 4

Operating systems provide utilities that
enable files to be compressed and
decompressed.
This is used when
compressing large files to be
transmitted across the Internet and is
commonly used to compress scanned
files.

Question 5

What is the disk defragmentation utility?

Answer 5

As the hard disk becomes full, read/write times slow down.
This is because files become fragmented as they are stored in different parts of memory.
The disk defragmenter utility rearranges the contents of the hard drive so they can be accessed faster, thus improving performance.

Question 6

What is the antivirus utility?

Answer 6

Antivirus is responsible for detecting potential threats to the computer,
alerting the user and removing these threats.

Question 7

What is the updating utility?

Answer 7

This utility ensures the operating system is kept up to date, with any updates being automatically installed when the computer is restarted.
Updates tackle bugs or security flaws so this ensures the system is less vulnerable to malware and hacking threats.

Question 8

What is the backup utility?

Answer 8

The backup utility automatically creates routine copies of specific files selected by the user.
How often files are backed up is also specified by the
user.
This means that in the event of a power failure, malicious attack or other accident, files can be recovered.

Question 9

What is open source code?

Answer 9

Open source code can be used
by anyone without a license and
is distributed with the source
code.

Question 10

What is source code?

Answer 10

Object code before it has been compiled.

Question 11

What is closed source code?

Answer 11

Closed source code requires the
user to hold an appropriate
license to use it. Users cannot
access the source code as the
company owns the copyright license.

Question 12

What are the advantages of open source code?

Answer 12

• Can be modified and improved
  by anyone
• Technical support from online
  community
• Can be modified and sold on

Question 13

What are the disadvantages of open source code?

Answer 13

• Support available online may be
  insufficient or incorrect. No user
  manuals.
• Lower security as may not be
  developed in a controlled
  environment

Question 14

What are the advantages of closed source code?

Answer 14

• Thorough, regular and
  well-tested updates
• Company owning software
  provides expert support and user
  manuals.
• High levels of security as
  developed professionally.

Question 15

What are the disadvantages of closed source code?

Answer 15

• License restricts how many
  people can use the software at
  once
• Users cannot modify and
  improve software themselves

Question 16

What must a user consider when choosing open/closed source software?

Answer 16

The suitability of the software to the task they will be using it for:
- Costs (implementation, maintenance, training, license)
- Functionality (features available, ease of use)

Question 17

What is a translator?

Answer 17

A program that converts high-level source
code into low-level object code, which is then ready to be executed by a computer.

Question 18

What do compilers do?

Answer 18

Compilers translate high-level code into machine code all at
once, after carrying out a number of checks and reporting
back any errors.

Question 19

What are the 3 disadvantages of a compiler?

Answer 19

• Initial compilation process is longer than
  using an interpreter or an assembler.
• If changes need to be
  made, the whole program must be recompiled.
• Compiled code is specific to a particular processor type and operating system.

Question 20

What is the advantage of a compiler?

Answer 20

Code can be run without a translator being present.

Question 21

What is an interpreter?

Answer 21

Interpreters translate and execute code line-by-line. They
stop and produce an error if a line contains an error.

Question 22

Describe the speed of an interpreter.

Answer 22

They
may initially appear faster than compilers as code is instantly executed, but are slower
than running compiled code as code must be translated each time it is executed with an
interpreter.

Question 23

When are interpreters useful?

Answer 23

Interpreters useful for testing sections of code and pinpointing errors,
as time is not wasted compiling the entire program before it has been fully debugged.

Question 24

Describe the devices an interpreter can be run on.

Answer 24

Interpreted code requires an interpreter in order to run on different devices. However, code
can be executed on a range of platforms as long as the right interpreter is available, thus
making interpreted code more portable.

Question 25

What is assembly code?

Answer 25

Assembly code is considered to be a low-level language
as it is the ‘next level up’ from machine code. Assembly
code is platform specific, as the instructions used are
dependent on the instruction set of the processor.

Question 26

What does an assembler do?

Answer 26

Assemblers translate assembly code into machine code.
Each line of assembly code is equivalent to almost one line of machine code so code is
translated on almost a one-to-one basis.

Question 27

What happens in lexical analysis?

Answer 27

Whitespace and comments removed
Code analysed for keywords/variables/contents
These replaced with tokens and information about the token associated with each keyword or identifier is stored in a symbol table.

Question 28

What happens in syntax analysis?

Answer 28

In this stage, tokens are analysed against the grammar
and rules of the programming language.
Any tokens that break the rules of the programming language are flagged up as syntax errors and added to a list of errors.

Question 29

What is an abstract syntax tree?

Answer 29

A representation of the source code in the
form of a tree.

Question 30

What is semantic analysis?

Answer 30

When logic mistakes within the program are detected.

Question 31

What happens in code generation?

Answer 31

The abstract syntax tree produced in the syntax analysis stage is used to produce
machine code.

Question 32

What is the aim of optimisation?

Answer 32

To make the code faster to execute, although this stage
can significantly add to the overall time taken for compilation.

Question 33

What happens in code optimisation?

Answer 33

This stage of compilation searches through the code for areas it could be made more
efficient.
Insignificant, redundant parts of code are detected and removed.
Repeated sections of
code may be grouped and replaced with a more efficient piece of code which produces the
same result.

Question 34

What is the danger with code optimisation?

Answer 34

Excessive optimisation may alter the way in
which the program behaves.

Question 35

What is a linker?

Answer 35

This is a piece of software that is responsible for linking external modules and libraries
included within the code.

Question 36

How does a static linker work?

Answer 36

Modules and libraries are added directly into the main file.
This increases the size of the
file. Any updates to modules and libraries externally will not affect the program. This
means a specific version of a library can be used

Question 37

How does a dynamic linker work?

Answer 37

Addresses of modules and libraries are included in the file where they are referenced.
When the program is run, the loader retrieves the program at the specified address so it
can be executed.
The advantage here is that files remain small and external updates feed
through to the main file; there is no need to rewrite the code.

Question 38

What are loaders?

Answer 38

Loaders are programs provided by the operating system. When a file is executed, the
loader retrieves the library or subroutine from the given memory location.

Question 39

What are libraries?

Answer 39

Libraries are pre-compiled programs which can be incorporated within other programs
using either static or dynamic linking.
Popular libraries provide mathematical and graphical functions.

Question 40

What are the advantages of libraries?

Answer 40

Ready-to-use and error free, so they save time developing the modules.
Can be reused within multiple programs.

Question 41

What does “reinventing the wheel” mean in context of a library?

Answer 41

Libraries are often used to provide a specialised range of functions which would otherwise
require a lot of time and effort to develop, so save programmers from having to ‘reinvent
the wheel’ and instead make use of others’ expertise.