I don't even know what generation of PDAs we are in. I believe it is the fourth. Regardless, they have come a long way. Sporting features, such as lithium-ion batteries, expansion slots, and GPS navigational systems, PDAs will eventually become as popular and widespread as cellular phones. This week, we're taking a look at Handspring's Visor Pro PDA. Although it is not a color unit, it has enough memory and expandability to make it worthy of the spotlight.