Personal Digital Assistants are hand-held personal computers that provide a host of personal information systems. PDAs are small, but versatile computers, slightly bigger in size than Palmtops and even Notebook computers. PDAs have their origin in British-made roaming device, Psion, a successor to Filofax, introduced in the 80s, for collecting POS (Position of Sales) data. Psion had several versions that define the device: a palmtop minicomputer with a small LCD display, tiny keyboard and some form of hand writing recognition.
The PDA in the present form with RISC-based microprocessor was first introduced with Apple Newton computers, a hand-held pen-input computer in1992. The outstanding feature of a PDA is its capability of taking small notes on-line through pen-inputs. This led to the development of character-recognition software like Graffiti (from 3COM), Jot (from Communication Intelligence Corporation) and Calligrapher (from ParaGraphs). Like any Pen computer, PDA can recognize free-form text graphics, which can be converted into editable digital information for subsequent storage and processing. It supports architectural sketching, CAD (Computer Aided Design), general sketching, etc.
A PDA can also be used as mobile calendar, telephone directory, and note pad for jotting down reminders. A modern PDA supports HotSynch feature for data downloading. Some products often support viewing of movies, listening to MP3 music, mobile telephone or Web-surfing and SMS (Short Messaging Systems.)
Most PDAs accept stylus-based input and few are with keyboards. Some supports both. The first category includes Apple MessagePad and Casio PDA (on GEOS), etc.
PDAs supporting keyboard include: HP200LX (on MS-DOS), Psion Palmtop (on Epoc), Sharp Zaurus (on Synergy), Motorola Marco (on Newton Intelligence), Casio PDA (on GEOS).
Systems supporting both pen-input and keyboard include: Fujitsu PoquetPad Plus (on MS-DOS), Motorola Envoy and Sony...