User Interface

User Interface

1. Command driven (Textual)

   • Teletypewriters (TTYs)
   • Video Display Terminals (VDTs)
   • Advantages
     • They may be implemented using cheap, alphanumeric displays.
     • More experienced users prefer to have direct control over the operations of the computer.
     • It is faster to issue a command sequence directly rather than searching through a menu.
     • Commands of almost arbitrary complexity can be created by combining individual commands. This allows command macros and command language programs to be written.
   • Disadvantages
     • Commands across different operating systems are seldom the same. Users must become familiar with different command languages.
     • For a novice it can be quite daunting and difficult to get even the simplest of operations performed.
     • Users always make mistakes in typing. This requires error handling and message generation facilities to be included in the command language processor. Systems interaction is through a keyboard. The interface cannot make use of pointing devices.
     • Users have to learn a command language which is sometimes complex. In some cases few users ever learn the complete language. The learning time for this type of interface is also greater than that for menu systems and GUIs. New users spend more time learning the interface than getting work done on the computer.

2. Menu driven

   • Menu driven interfaces present the user with a list of options from which to select. The user may make this selection via a keyboard or a pointing device such as a mouse.
   • Categories
     • Full Menu Screen
       • These menus usually present the options to the user as a sequential list which occupies the entire screen. This is usually followed by a message prompting the user to select one of the options.
     • Bar and Pull-down Menu
       • The main options available to the user are presented as pads on a horizontal bar across the screen. When the user selects one of the pads on this menu, the second-level options are displayed in a pull-down menu.
     • Pop Up Menu
       • These menus usually appear as a box with one of the options already selected. When the user points to the box with a mouse and presses the mouse button, the other options are displayed in a list. The user can then select the required option with the mouse.
   • Advantages
     • The user is presented with a choice and so does not need to remember any commands. This interface is suitable for beginners and knowledgeable intermittent users.
     • The opportunities for making serious errors are reduced since the user does not have to type in any commands.
     • Menus can utilise special pointing devices such as mice, trackballs and light pens. Thus the typing effort required can be kept to a minimum.
     • Context-dependent help can be provided since it is possible to keep track of the user's position in the menu system and link this to a help system.
   • Disadvantages
     • They are not as concise as command-driven interfaces. Accomplishing a task in a menu driven interface generally involves more steps than is required for doing the same task in a command-driven interface.
     • If there are a large number of options available, it may difficult to structure the menu system so that the user is not presented with an unacceptably large menu.
     • Tasks which involve logical operators (such as 'and', 'or') may be awkward to express in a menu system.

3. Graphical user interfaces (GUI)

   • Windows
   • Icon
   • Pointer
   • Alerts and Warnings
   • Dialogue Boxes
   • Menu
   • Advantages
     • Typical user learning time is short.
     • Users feel in control of the computer and are not intimidated by it.
     • Users get immediate feedback on their actions so mistakes can be detected and corrected quickly.
     • Icons help users to recognise what objects are meant to represent.
   • Disadvantages

4. Special purpose

   • Touchscreens
     • Also foundAllows users to navigate menu system of art works, etc. by touching screen with finger.
     • Customers can now produce their own prints by navigating the menu and sub-menu printing system.
     • Museums
     • Travel Centre
     • Photographic outlets.
   • Speech
     • Visually and physically disabled users
     • Users can get audible sounds and words from the computer.
   • Natural language
     • Speech input systems
     • The most natural interaction style. Speech recognition software is improving greatly but is still not perfect.
   • Disadvantages
     • Only has one purpose