Applications Generation

What Applications Generation covers

Applications Generation is examined on component 01 of OCR Computer Science, Computer systems. 64 recall questions across 5 subtopics.

The 5 subtopics

Each one has its own page.

• Applications and utilitiesRecall questions on application software and utility programs, common utilities, defragmentation on hard disks and solid state drives, lossy and lossless compression, generic and bespoke software, and justifying applications for a given purpose.Open →
• Open source and closed sourceRecall questions on open source and closed source software, the arguments for and drawbacks of each, whether open source means free, how companies profit from open source, security arguments, and choosing between them for a scenario.Open →
• Translators: interpreters, compilers and assemblersRecall questions on assemblers, compilers and interpreters, the differences between compiling and interpreting, debugging, speed and distribution, bytecode, one-to-one assembly translation, portability, and choosing a translation approach for a project.Open →
• The stages of compilationRecall questions on lexical analysis, tokens and the symbol table, syntax analysis and the abstract syntax tree, syntax and semantic errors, code generation, optimisation and its cost, and which errors are caught at compile time.Open →
• Linkers, loaders and librariesRecall questions on linkers and loaders and the difference between them, libraries and their advantages and disadvantages, static and dynamic linking compared, and patching a vulnerable library under each kind of linking.Open →

What you need to know

Answer each one before you reveal it.

Take Applications Generation further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• A compiler vs An interpreter

  A compiler: a translator that converts the whole of a source program before any of it runs. An interpreter: a translator that converts and runs a source program one statement at a time.

• An assembler vs A linker

  An assembler: a translator that turns mnemonic instructions into the machine code they stand for. A linker: a program that combines separately translated modules into one executable.

• Static linking vs Dynamic linking

  Static linking: copying library code into the executable when it is built. Dynamic linking: leaving library code out and locating it in shared form at run time.

Questions from this topic

Each one with the model answer underneath.

1. 1

   What is application software?

   Model answer

   Software that carries out a task the end user actually wants done, rather than running or maintaining the computer itself - for example a word processor, a spreadsheet, a web browser, a database front end, a photo editor or a game. It relies on system software to reach the hardware.

2. 2

   What is a utility program?

   Model answer

   A small piece of system software that performs a specific maintenance, optimisation or housekeeping task on the computer, usually supplied with the operating system or added to it. Utilities keep the machine working well rather than doing work the user set out to do.

3. 3

   Name five utilities and say what each does.

   Model answer

   Any five of: a compression utility, which reduces file size for storage or transmission and restores it afterwards; a disk defragmenter, which rearranges the blocks of each file so they are contiguous on a magnetic disk, reducing head movement; antivirus or anti-malware software, which scans files and running processes against known signatures and suspicious behaviour and quarantines threats; a backup utility, which copies data to another medium on a schedule and can restore it; a file manager, which lets the user view, move, rename, copy and delete files and folders; encryption software, which scrambles files so they are unreadable without the key; and a disk clean-up utility, which deletes temporary and redundant files to reclaim space.

4. 4

   Why does defragmentation improve performance on a magnetic hard disk but not on a solid state drive?

   Model answer

   On a magnetic disk the read-write head must physically move to each fragment, and a file scattered across the platter costs many seeks; putting the blocks back together removes that movement. A solid state drive has no moving parts and reaches any block in the same time, so there is nothing to gain. Worse, defragmenting one causes a large number of unnecessary writes, and flash cells have a limited number of write cycles, so it shortens the drive's life.

5. 5

   Distinguish between lossy and lossless compression, and say which a compression utility for program files must use.

   Model answer

   Lossless compression encodes the data so that the original can be reconstructed exactly, bit for bit. Lossy compression discards information judged unimportant, so the restored file is only an approximation of the original. A compression utility handling program files, documents or spreadsheets must be lossless, because a single altered bit would break the program or corrupt the data; lossy compression is only acceptable for media such as images, audio and video where small losses of detail are tolerable.

6. 6

   Distinguish between generic (off-the-shelf) and bespoke (custom-written) application software.

   Model answer

   Generic software is written to be sold to many customers, so it is cheap per copy, available immediately, well tested by a large user base, and supported with documentation and training - but it may not do exactly what one organisation needs and may carry features it will never use. Bespoke software is commissioned for one organisation, so it fits their process exactly and can be changed on request, but it is expensive, takes a long time to develop, and starts with no user community, no third-party support and only the testing its developers did.

What is inside Levo

Six ways to work the same material.

Applications Generation revision questions

What does Applications Generation cover in OCR A-Level Computer Science?

5 subtopics: applications and utilities, open source and closed source, translators: interpreters, compilers and assemblers, the stages of compilation and linkers, loaders and libraries. Each one has its own page with questions and model answers.

How is Applications Generation organised?

By the OCR H446 specification, subtopic by subtopic, so it matches the order you are taught it in.