Newbie problem :)

[skimask]

PortA.0 on the 16F877A (as well as many others) is an analog input by default and as such, will not work with 'digital commands'.
You must change it to a digital input.
This is also true of many PICs with built-in ADC's.

[paul borgmeier]

>>You must change it to a digital input. (from SkiMask)

He is correct - to do this add

ADCON1 = 6

before your TRIS commands and all should be well (see datasheet PORTA section for explanation)

[sokrad]

Thank you, it work's.