The earliest computers I ever used didn't have keyboards or video screens. I haven't seen a computer in years that reads JCL (Job Control Language) commands from punched cards, like most all the early computers used.
A few years later a new generation of computers appeared, and keyboards and video screens became the norm. Computer programs were re-written to accept keyboard input. We learned to type our commands.
Still a few years later, the computer mouse appeared. Software was re-written, and then entire operating systems were re-written to accept this new method of input. We no longer have to type archaic strings of letters and numbers in order to start a program or to switch to a different disk drive. Today, we click the mouse.
Still a newer revolution is now upon us.
The mouse is slowly being replaced by touch; now you can point at, tap, or drag an object on the screen with your finger, a handy device that you’ve used all your life. Anyone who has used an Apple iPhone or iPod Touch already understands this change. While not perfect in every way, touching a computer screen is generally more intuitive than using a mouse. I recently purchased a shirt-pocket sized computer that runs Windows XP. There's not enough room left in the shirt pocket for an external mouse so this tiny powerhouse of a computer uses a touchscreen. I find Windows XP to be very intuitive when used with touch.
The iPhone and the iPod Touch and a number of other handheld computers use touch input today. The newly-announced-but-not-yet-shipping Apple iPad will use the same. The iPad is expected to become very popular. Computer programs are being re-written to accept touch input.
Touch changes the way we use computers and especially the way we use the World Wide Web. We need to get used to it, and vendors need to design their applications assuming this reality.
I suppose the next revolution will be voice input. The technology isn't there yet; voice input is available today but doesn't work all that well. Like all the other data input changes in our recent past, voice input will improve and eventually become the preferred method of input. Remember Scotty trying to use the ancient computer in an episode of Star Trek?
Someday we will all talk to our computers. Until then, I'll settle for touch.