just a serial port? surely u would need a/d converter to analyse the signal.
Oh well, if you know better, then don't listen to me.
What is it you wanna get from analyzing it?
my idea is to send signals from the light sensors to the computer which sends signals by analyzing that data to motors to decide whether to move left right forward.
If you want to decide whether you're over a white or black area, you only need to see if you have more than so-and-so-much light reflectance - using an A/D-C for that is bordering the downright silly and it adds a huge amount of overhead.