1.2.1 systems software (virtual machine exam q's)

Question 1

When translating computer languages, intermediate code may be produced.

Explain the need for intermediate code and its purpose in a virtual machine. (8 marks)

Answer 1

Intermediate code:
- simplified code that is between high level & machine code which is produced by compiler
- This code runs on any computer and allows portability between machines
- Allows sections of code to be written in different languages by different programmers
- suitable for specific tasks

Virtual machine:
- theoretical computer which provides an environment in which a translator is available
- Uses an interpreter to run the intermediate code
- A translator is used to convert code from one language to another (from source code to object code)

Question 2

Early computers were programmed in binary machine code. Today most programmers use high-level languages.

Explain why the programmer could use intermediate code for the final product. [3]

Answer 2

• Can be used in a virtual machine
• Portable / can be used on any machine
• Protects source code from being copied

Question 3

A software development company is building an operating system for a mobile phone that is in the process of being designed.

Explain how the developers could use virtual machines. [2]

Answer 3

• Developers can run their OS on a software implementation of the phone to test it until the physical machine is ready.

Question 4

Explain why the programmers of anti-virus software may make use of virtual machines when developing the updates. [3]

Answer 4

• Allows them to run the update on a number of different systems / OSs without needing multiple physical machines.
• They can put viruses on the VM to test if the update can catch them but protect the physical machine from virus / the VM can quickly be reset to its original state.

Question 5

In order to keep up to date with the latest virus threats, company is continually updating their software.

The programmers use an Extreme Programming approach when developing the updates.

Explain what is meant by Extreme Programming and why it is a suitable approach in this case.

Answer 5

– Extreme programming is a software development methodology (its an agile paradigm)
– Focus is on good quality code
– it is designed to allow development to respond to changing user requirements.
– Involves paired programming
– Program is regularly reviewed / iterative
process.

Suited to this scenario as…
– Types of virus/threat is continually changing / updating
– In order to detect virus effectively there needs to be an emphasis on code
quality.

Question 6

Describe what is meant by the term JavaScript.[2]

Answer 6

• A programming language that adds interactivity to a webpage and works alongside/can be embedded into HTML with

   tag. Also works with CSS. It runs in a web browser

Question 7

Explain why it is usually the case that JavaScript is interpreted rather than compiled. [2]

Answer 7

JavaScript is likely to be run on a variety of machines with different processors / architectures.
Compiled code is machine dependent whereas interpreters run on high level code which is machine independent.