A Command Line interface requires the user to type commands into the computer a line at a time. The interface is a cursor on the screen at which text commands can be typed in.
Several lines of commands can be written in a macro or script that can then be invoked or called in one command.
The language of the commands relate to functions of the operating system.
Command line interfaces can be very powerful in the hands of an expert, but very frustrating to a beginner or someone inexperienced with the command language.
A menu selection interface provides the user with a series of options - usually indicated by a numbered list - for the user to select from and then execute. Sometimes the user inputs the relevant key - a number - or selects by moving the cursor - by a mouse or cursor key press - to select the option they wish to execute.
A form interface or a forms dialogue interface that provides inputs and outputs as a series of fields. The user can enter data, read data and perform an execute command when the form has been completed.
The forms often imitate the look of printed paper forms.
Examples of a form interface are database record entry forms, query forms etc.
A Graphical User Interface (GUI) is - these days - the normal way to access a computer. The user is presented with a screen full of boxes, icons, images, links etc. and the user interfaces with these by inputting from the keyboard, the mouse, with voice or by touch.
Each element on the window enables discrete functions or actions to be called and executed. For example an icon will open a new program, or an icon will invoke a feature of the program, like save.
Most GUI's can be categorised as a "WIMP" (Windows, Icons, Menus and Pointers). Touch screens GUIs have just added a new pointer - the finger. A WIMP is based on a two dimensional display on a screen. There are prototypes dealing with 3D interfaces, sound based interfaces, eye tracking interfaces - wearable interfaces.
Sometimes know as "wearable computers", "body-borne computers" or "wearables". These are miniature electronic devices that are worn by the bearer under, with or on top of clothing.
Essentially the interface has not changed from the GUI or WIMP model, except that the pointing is done only by a touch screen and other movements - e.g. eye tracking, blinking - and also voice commands are a standard part of the interface. The display is sometimes a projected screen on special glasses or a miniature screen on a wrist watch.