i) Keyboard is the most common form of input devices. It was originally designed in the last century. Since then, only minor improvements have taken place in key board design.
ii) Pointing devices: These are used to indicate a point on a screen for example, to make a selection from a menu. They include: The light-pen (where the tip of the pen is touched on. the screen); The touch-screen (touched directly by finger, pen etc.), and the mouse (moved around the desk or other flat surface to move a cursor on the screen, with the required position marked by pressing a button on mouse). These devices will obviously work with appropriate interactive computer software.
iii) Voice input is now in a stage of development where commercial systems are becoming available. It may take some more time for these systems to be trained to recognise each user's voice and are presently limited to vocabularies of a few thousand words. In other words, voice input is only in experimental stage of development. It may take some years before it is made operational.
iv) Barcodes These incorporate information in a pattern of stripes, produced and read by special equipment. These are widely used in library issue systems and are slowly gaining wider use for general data transfer, particularly as a means of 'publishing' computer programs. To the extent they are used in library automation, they can be considered as data input devices.
v) Optical Character Recognition This method has now developed to a stage, when it can be used as a practical means for routine entry of large quantum of print on paper information into computer systems. Unless special steps are taken, error rates are very high in this technique. Hence, standardisation of input is highly necessary.