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A user interface is a program, or suite of programs, that allows a user to interact with a computer in many ways. User interfaces allow users to:

• copy, delete, move, sort, rename, and search for files or folders
• access system settings such as hardware preferences
• multitask by having more than one application open
• switch between tasks
• access error and help messages when necessary
• customise the interface, for example by changing the background colour or layout (not available with command line interfaces (CLIs))

There are two main types of interface:

• graphical user interface (GUI) - sometimes known as WIMP (Windows, Icons, Menus, Pointers) interface
• command line interface (CLI)

Graphical user interface

A GUI is familiar to most users of PCs and laptops. GUIs feature a desktop, where everything is displayed. Applications run in windows and all objects (apps, hardware and files) are represented by icons. Application features are accessible through the use of menus. Users interact with the interface by using a mouse and on-screen pointer.

GUIs are powerful and easy to use but require a lot of processing power.

Command line interfaces

CLIs are text-based. Users control the computer by typing in commands.

CLIs require little processing power and are extremely powerful, but it can take longer to learn how to use a CLI than a GUI. Originally, most interfaces were CLIs. They still exist within modern operating systems, for example the command prompt app in Windows, and Terminal in macOS.

This is an example of executing a command in Linux:

1. user@bash: pwd
2. /home/myCSdata
3. user@bash:

Line 1 accesses the shell, which is used to enter and run the commands. This shell is called ‘bash’. The command ‘pwd’ instructs the operating system to print the working directory.

Line 2 lists the contents of the working directory.

Line 3 stops the shell.

CLIs are typically used by system managers or other specialist users. Once you know the commands it is quicker to use a CLI to manage the operating system than to go through many menu levels.

Other interface examples

Mobile user interfaces are similar in many ways to GUIs except that they respond to touch. Fingers are used to open programs and interact with them. Gestures such as swiping are used to scroll within documents. Pinching and stretching are used to resize images.

Mobile UIs are found on smartphones and tablets.

Voice user interfaces are becoming increasingly popular as a natural way of interacting with technology. They are used by voice device assistants. Mobile UIs can also respond to voice commands.