User Interfaces – AS Computing Revision (F451 and F452)

Definitions and Types

User Interface comparison

User Interface comparison (Photo credit: phempsall)


  • UI – User Interface
  • HCI – Human-Computer Interface
  • An interface is what allows humans (users) to interact with computers
  • They let the user input information and also output information to the human
  • There are several types: GUIs, NLIs, Command Line, Menu-Driven, and Form-Based


  • Graphical User Interfaces (obviously)
  • They use windows, icons, menus and pointers (WIMP)
  • They’re easy to use and understand, and intuitive
  • Many advanced (or risky) functions are hidden, so the user can do their everyday tasks without being confused by the presence of experts-only features
  • They often have some kind of contex sensitive help feature
  • Windows are overlapping frames applications run in, that can be moved around on-screen, resized and displayed in groups
  • Icons are small images which represent applications – they’re easy to recognise and click, so the user doesn’t have to type commands to use the features
  • Menus allow users to select options from a list (in GUIs, the menus tend to be drop down boxes, for example)
  • Pointers are cursors / arrows on-screen, which respond to the mouse and allow the user to interact with the GUI

Menu-Driven Interfaces

  • These are interfaces that are made up entirely of menus
  • (Not to be confused with GUIs, which can have menus, but don’t use them all the time)
  • Screens with lists of options on them are connected in hierarchical layers
  • This type of interface severely limits what options the user has access to, so it’s useful for restricting users
  • They tend to be simple and intuitive to use, so they’re good for beginners

Form-Based Interfaces

  • ‘Forms’ are displayed on-screen, to mimic the appearance of a form on paper
  • There will be fields such as text boxes, radio buttons and check boxes
  • There will also be explanatory labels and maybe instructions
  • This type of interface is also helpful to beginners, and very restrictive
  • The presence of the empty fields on the screen makes it unlikely that the user will forget to enter something
  • These interfaces often make use of validation (and verification)


  • Natural Language Interfaces
  • They let users communicate with the computer in their own language
  • The interfaces are designed to understand human phrases and syntax
  • A lot of processing power is required to translate your instructions into something the computer can understand, so it may run slowly
  • They can be pretty inaccurate, too! (Slang, or accents can confuse them)
  • Speech-recognition software is an example, although typing requests in the same way you’d say them also counts
  • You may find them as part of knowledge-based/expert systems

Command Line Interfaces

  • You give the computer instructions by typing specific commands
  • This will involve learning the commands
  • They’re not very easy to use or intuitive at all
  • Only experts tend to use them
  • Once you know the commands, they’re fast to use (no navigating windows of menus of icons over and over again)
  • They place no restrictions on the user
  • As a result you could mess something up big time by typing the wrong commands
  • It doesn’t take loads of processing to understand what the user is telling it to do – the commands are very specific, and speak directly to the operating system

Worth Mentioning Here

  • Common interfaces are interfaces that several different programs implement, in an effort to be easier to use – the idea is that the user learns the interface in one program, and doesn’t have to learn different interfaces for the other programs (which is why Save and Save As are always found under File, in Microsoft Office programs (well… the old versions of them, anyway)
  • When a question asks for a “form of output”, it doesn’t want you to suggest some output devices – it’s asking for output formats such as light, sound, pictures, text, video, graphs, reports or animations (it’ll almost always want you to say why, as well)

About Matt

I like writing, filmmaking, programming and gaming, and prefer creating media to consuming it. On the topic of consumption, I'm also a big fan of eating.
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