I've seen some schematics and see some pins using Vcc, while others Vss. What's the difference between two?

 

its just different names for different transistor technologies.

Vcc is the conventional name for the collector supply of a bipolar transistor and Vss is the conventional name for the source supply of an field effect transistor.

 

so all 5 V rite?

 

if that is what the maximum voltage of the chip/part is, then yes

 

I think you'll find that Vss is usually 0V, Vdd is the 5V(3.3V/3.0V)

 

Personally I really hate these silly labels, and I never use them - I label +5V, GND (or 0V) and -5V, these are much more sensible than Vcc, Vdd and Vss.

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i agree with u Nigel but most of the things that are conventional are silly!!!

we are taught these things in college and we have to work with them everyday and thats why they never disappear. it looks like we will have to live with them!