A hand held computer of a type used for such activities as taking inventory, recording signatures on delivery, keeping a route agenda, etc. has a large screen and preferably is without a built in keyboard. The tablet type computer is thin in profile, light in weight and is easily carried and used. Programming in the computer enables an operator to select from various forms available for display on the screen, enables character recognition for items printed on the screen using a conductive stylus, enables the recording in memory of signatures, graphics or any other material entered on the screen, and enables other convenient functions. Certain preferred features of the computer enable it easily to be converted into a full function desk top computer with a keyboard, expansion module and stand.