1.2.2. Applications Software: 1.2 Software and Software Developments: Computer Science A-Level OCR

What is the difference between applications and systems software?

Applications software is utilised directly by the end-user whereas systems software ensures the high performance of the computer.

Give 3 examples of utilities.

Three from:

- Compression

- Disk defragmentation

- Antivirus

- Automatic backup

- Automatic updating

Give one advantage of using closed source code.

- Thorough, regular and well-tested updates.

- Expert support and user manuals from company.

- High levels of security as it is developed in a professional, controlled environment.

State two features of open source code

- Does not require a license to be used.

- Distributed with the source code.

- Can be modified and sold on.

Give two advantages of using compiled code over interpreted code.

- Faster to execute.

- Does not require compiler to run.

Give two advantages of using interpreted code over compiled code

Two from:

- Is platform independent.

- Runs instantly without time waiting for compilation.

- Useful for debugging.

What is assembly language?

A low-level language that has almost a one-to-one relationship with machine code. It is platform specific.

What are the stages of compilation?

● Lexical analysis

● Syntax analysis

● Code generation

● Optimisation

What happens during syntax analysis?

- Tokens are compared to the rules of the programming language.

- Syntax errors are identified.

- Symbol table updated with more details.

- Semantic analysis (finding logic errors).

What are the similarities and differences

between static and dynamic linkers?

Similarities: Both link external modules and libraries to main program.

Static: Library code copied into the file. File size increased.

Dynamic: Addresses of libraries included within file. External updates automatically feed through to main program.

Give three advantages of using libraries.

- Error-free

- Save time

- Re-usable

- No need to ‘reinvent the wheel’

- Designed by experts

Describe the function of a loader.

Provided by the operating system, a loader retrieves the library or subroutine from the given memory location.

What is the purpose of the optimisation stage of compilation?

● Reduce execution time

● Reduce inefficient sections of code

● Remove redundant code