Exam Board:
OCR A-Level
2.2 - Applications Generation
Specification:
Computer Science H446
Watch on YouTube:
Application software
Utilities
Open & closed source
Translators
Stages of compilation
This topic explores key types of software and how they support computer systems and users. It explains different kinds of applications, utilities, translators and compares open and closed source software. Another important concept is compilation, with knowledge required of its different stages, as well as linkers, loaders and software libraries.
Applications Software
Applications software allows users to carry out productive or creative activities such as document editing, data analysis, communication or media creation.
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Common examples include word processors (e.g. Microsoft Word or Google Docs), spreadsheets (e.g. Excel or Sheets), database management systems (e.g. Access), web browsers (e.g. Chrome or Safari) and graphics editors (e.g. Photoshop).
Applications can be general-purpose, serving many uses, or special-purpose, created for a specific function like payroll or medical record management.
Utilities
Utility software is system software designed to maintain, optimise and manage a computer’s performance, often running in the background to support the operating system.
Examples include security tools like an antivirus, backup, compressors, disk management utilities and defragmenters.
Defragmentation is the process of reorganising files on a hard drive so that parts of each file are stored together in contiguous blocks, improving access speed.
Open Source & Closed Source
Open source software has its source code (the actual code written by its developers) made publicly available, allowing users to view, modify and share it freely.
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An open source licence encourages collaboration, transparency and community-driven improvement. However, it may lack official technical support or guaranteed updates.
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Closed source software has its source code private, restricting modification and redistribution. It is usually sold commercially with paid licences, regular updates and dedicated technical support.
Bug fixes and quality assurance are out of the user's control, being managed by the developer. Support may end without warning.
Translators
Translators are programs that convert source code written in one programming language into another form that the computer's CPU can understand - typically machine code (binary).
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An assembler translates assembly language into machine code that the CPU can execute directly.​​​
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An interpreter translates and executes high-level code in a line-by-line method, stopping when an error occurs.
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A compiler translates the entire high-level program into machine code before execution, producing an executable file.
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Stages of Compilation
Compilation is a complicated process to convert high-level program code into machine code. It consists of four key stages:
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Lexical analysis breaks the source code into tokens, such as keywords, identifiers and symbols. In this stage unnecessary characters like spaces or comments are removed.​​
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Syntax analysis checks that the token sequence follows the grammatical rules of the programming language, building an abstract syntax tree.
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Code generation converts the syntax tree or intermediate code into machine code the CPU can understand.
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Code optimisation improves the efficiency of the generated code, for example by reducing redundant instructions or improving execution speed.
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Compilation also requires additional programs such as a linker and loader and the use of libraries.
Questo's Key Terms
Applications: database, word processor, web browser, graphics manipulation, spreadsheet software, presentation software
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Utilities: defragmentation, system cleanup, file manager, device driver, security tools
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Open & Closed Source: source code, open source, closed source
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Translators: assembler, interpreters, compiler, machine code
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Stages of Compilation: lexical analysis, token, syntax analysis, abstract syntax tree, code generation, code optimisation, library, linker, static linking, dynamic linking, loader
Did You Know?
Grace Hopper, a US Navy rear admiral, is credited with creating one of the first compilers in 1952 and coining the term 'compiler'. She also helped develop the languages FLOW-MATIC and later COBOL, which is still used today.
