A medium (plural media) is something which can be used for presentation of information. There are two basic ways to present some information.

1. Unimedium presentation - In this case, a single medium is used to present information. For example, a stereo system is a Unimedium device because it presents information by using only sound medium. Similarly, a book having only text (no diagrams) is also a unimedium device because it presents information by using only text medium.

2. Multimedia presentation - In this case, more than one medium is used to present information. For example, a TV system is a multimedia device, because it presents information by using sound and video media. Similarly, a book having both text an diagrams is also a multimedia device because it presents information by using text, graphics and images.

Obviously, multimedia presentation of any information greatly enhances the comprehension capability of the user, because it involves the use of more of our senses. For example, students in a class can understand a lecture better if the lecturer draws illustrative diagrams on the board while delivering his/her lectures.
In case of computer systems, the commonly used media for the purpose of storage, access and transmission of information are:

1. Text (alphanumeric characters)
2. Graphics (line drawings and images)
3. Animation (moving images)
4. Audio (sound)
5. Video (video graphed real-life events)

Hence, in the computer world multimedia refers to the use of more than one of the above listed media for information presentation to the computer users-such as text and sound.

MULTIMEDIA COMPUTER SYSTEM

A multimedia computer system is a computer system which has the capability to integrate two or more types of media (text, graphics, image, audio and video) for the purpose of generation, storage, representation, manipulation and access of multimedia information. In general, the data size for multimedia information is much larger than textual information, because representation of graphics, animation, audio or video media in digital form requires much larger number of bits than required for representation of plain text. Due to this, a multimedia computer system requires:

1. Faster CPU (for quicker processing of larger amount of data)
2. Larger storage devices (for storing large data files)
3. Larger main memory (for running programs with large data size)
4. Good graphics terminals (for displaying graphics, animation and video)
5. I/O devices required to play any audio associated with a multimedia application.

All multimedia computer systems need not have all the features listed above. For example a computer system, which does not have to handle audio and video media can still be called a multimedia computer system, because it can still handle multiple media (text and graphics). However a full—fledged multimedia computer system must be capable of handling all types of media discussed above, and hence, must have all the features listed above.

MULTIMEDIA COMPONENTS

Text - Alphanumeric characters are used to present information in text form. Computers are widely used for text processing. Text processing with the use of computers generally involves the following hardware devices.

1. Keyboards are most commonly used to input text data.
2. OCRS (Optical character Recognizers) are used for direct input of printed text to computers.
3. Computer screens are used to display text information.
4. Printers are most commonly used to output text in hard copy form.

SOFTWARE REQUIREMENTS FOR TEXT

The following text processing capabilities are highly desirable in a multimedia computer system for better presentation and use of textual information.

1. Text editing - Text editors and word processing packages are used to generate, edit and properly layout a text document.

2. Text style - Presentation of text information can be made more effective by using text of various sizes, fonts and styles (bold, italics, shadow etc). For example, newspapers use a good combination of all these styles to better highlight more important news than less important ones. Similarly, in a book a combination of various text styles are used to put more emphasis on certain words or phrases than the remaining text.

3. Text searching - Usage of text information can be greatly enhanced by text searching feature. This feature allows the user to enter a word or phrase and the computer quickly finds and displays that part of the text where the word or phrase appears in the textual information, with the word or phrase highlighted.

4. Hypertext - Both presentation and use of textual information can be greatly enhanced by using hypertext feature. This feature provides great flexibility of structuring and accessing computer-based text information. It generalizes the concepts of “footnote” and “cross reference” of traditional information (or document).
It allows users to obtain information by clicking on an anchor (a word or phrase linked to another document) within a document. An anchor is often called a “hot word”. This means if the user wants more information about a particular hot word, he/she can select that hot word (usually with a mouse pointer), and open a window with additional text explaining that word or phrase.

5. Text importing and exporting - The task of creating a textual document can often be greatly simplified, if the document preparation software has text-importing feature. This is because some of the text you want to incorporate in your document may already exist as a file created by a word processor or a database file. The file (partly or fully) can be simply imported into the new document at the desired location, instead of retyping the entire text again.
If the imported file is large, it will result in enormous saving of time and effort required to prepare the new document. Similarly, text exporting feature is very useful in allowing other packages to use an existing document partly or fully.

GRAPHICS
Computer graphics deals with the generation, representation, manipulation and display of pictures with the aid of a computer. Graphics is an important component of multimedia because a picture is a powerful way to illustrate information. For example, in a multimedia application meant for educating small children, displaying the photograph of a horse along with its textual description, makes the illustration much more effective. Without the photograph it will be very difficult to explain, using only text how a horse looks like. Similarly displaying the photograph of an employee along with her name, address, sex, age etc. from a company’s database of employees makes the employee information much more effective.