Square wave input to PC

I have a circuit which outputs a square wave signal upon entering a given state. I am looking for the simplest method of inputting this signal to my computer for access in a BASIC, VB or C program, or other existing software interface. The final goal will be to count the number of times the circuit was in the activated state over a given period.

Not totally new to electronics at the component level, but dealing with computer I/O is a bit new.. definitely appreciate any help!

hi,
Does your computer have a parallel and/or serial port?

What's the squarewave frequency? You can use built-in serial/parallel ports as [I believe] Eric is alluding to. You can also use a cheap USB-serial converter cable, with the squarewave going to the RX pin. Alternately, you could connect it into the microphone/line-in audio port on your soundcard (with a few interfacing components).