The key five differences between tablet PCs and PDAs centre on the following:

• Size – PDAs are almost all handheld devices, whereas tablets are larger can be held with one hand or across the forearm.
• User interface – Generally you cannot use your fingers with a PDA; instead a stylus should be used. In contrast tablet PCs are optimised for use of fingers rather than a mouse.
• Build – PDAs are lightweight (although Palm supplied a variety of high-end devices) whereas tablet devices can range from lightweight and flimsy (some cheaper Android tablets) to heavy and sturdy (some Windows tablet PCs).
• Operating system – A tablet PC version of Windows 7 is available for suitable devices, although the most common tablet operating systems currently are Android and iOS, the operating system used on the iPad.
• Purpose – You’re limited with what you can achieve with a PDA, whereas the various types of tablet PCs have software available to assist you in performing almost any task.

Note that within the tablet PC category you will find further differences when comparing Windows 7, Android and iOS devices.

So as you can see, there are considerable differences between PDAs and tablets, just as there are between tablets and desktops.

Source: author experience

PDA image: http://upload.wikimedia.org/wikipedia/commons/6/64/Pda.png

Tablet PC image: http://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/VIA_Tablet_PC_Reference_Design.jpg/573px-VIA_Tablet_PC_Reference_Design.jpg