In order for an application to be successful, developers always try to make their product easy to use and attractive to the user. They spend a lot of time working on how the interface looks and feels to the user and they will take into consideration things such as how the end user interacts with the software. 

The end user wants an application that will complete a task quickly and easily. There are a variety of approaches taken to the development of a user interface and the interface type chosen will often depend on a variety of factors such as:– 

• User ability 

• Range of input and output devices available 

• Processor capability 

• Memory capacity 

The WIMP interface (shown in figure 1.1) will allow the user to communicate with the computer using:– 

• Windows – These represent an active area of the computer screen which is opened up to display some form of activity; perhaps in the form of processing in a program or perhaps presenting a range of files and folders. More than one window can be open on screen at any one time and it can be moved around or closed down. 

• Icons – These are small pictures used to provide a graphical representation of an application or activity. An icon can be selected by moving a selection tool over the top of the icon and an activity can be started through double clicking on the icon. 

• Menus – A menu is used to present an end user with a range of options. The menu system is used to group related options / actions together. A variety of menu types may be presented to the end user including pop-up menus (often used to present a series of shortcuts to the user when they right click on the computer screen) and pull-down menus (normally used to present a range of options / items in a submenu, linked to a menu title presented across the top of a screen). 

• Pointers – A pointer will move around a computer screen based on the movements instigated by the end users manipulation of a peripheral device such as a tracker pad or a mouse. The pointer can be used to select an item on screen, (for example an icon or a menu option) it may change shape. The user can then initiate further action to indicate their desire to select said item; perhaps a left button click or double click 

A command line interface, such as the one shown in figure 1.2 above, allows the user to type commands which the computer will execute. Commands are usually fixed in structure (syntax) and limited to one line. Users require an intricate knowledge of the internal operation of the computer in order to use a command line interface and they must be well versed in the range of acceptable commands made available to them using the interface. Instructions can be combined to carry out more complex tasks. 

A form dialogue interface will output prompts and response fields to the user on screen. The user must then provide input via each of the empty fields, which must be completed. A forms dialogue interface will use the following methods to secure the required input from the end user:– 

• Response field – a position on the forms dialogue box where the end user will enter a response. The may move the cursor from field to field, e.g. with a mouse click or perhaps using the tab key on a keyboard. 

• Prompt – a prompt may appear for the end user at the position where data entry is required. The prompt may be in the form of a flashing cursor in a response field. 

• Error messages – used to inform the end user there has been an error in the data entry process. The most user friendly error messages will include some form of diagnostic information for the end user. 

Text may be input to digital devices using a variety of methods; the most common being via a keyboard. The QWERTY keyboard is the most common keyboard format available on digital devices; it will incorporate letters, digits and a range of special characters. Some devices may however have a separate numeric keypad. The set of characters represented on a digital device at any one time is known as the character set of that device.

ASCII (American Standard Code for Information Interchange) is a common character set on digital devices. The ASCII code uses 7 bits which gives 32 control codes and 96 displayable characters or symbols. The eighth bit can be used for error checking. The depression / selection of a key on any device will generate a digital signal representing the character code. When a symbol representing a particular character is to be printed or displayed on the screen of a particular device the character code is converted into the appropriate symbol .

Sound input – most digital devices are now supplied with simple microphones for recording sound. Since sound is produced by the vibration of air it can be said to be analogue in format (i.e. it is a continually varying signal).

The electrical output from a microphone also consists of a continually varying signal in the form of voltage. Devices such as personal computers, laptops, tablets or smartphones all store data in digital format so conversion of the analogue signal and the digital data is needed. 

This is achieved through the process of sound sampling where special hardware (Microphone) measures the level of the sound many times per second and then records this as a numerical value . These numbers are played back via the speakers to recreate the sound digitally.

The more samples we capture per second the better the file quality and the larger the file size.

It is common place now for digital devices to have a camera incorporated for the recording of digital still and digital video images. Digital video cameras have two main components; the camera, which is the image capturing component, and the recorder which is the component of the video camera that stores the captured video images. The image is recorded using the digital camera. The captured image is then transmitted into computer pixels which is then stored in whatever media storage is available to the digital video camera.