mohammad zamani asked:
"how can i send ascii code to 8051 with pc keyboard?"

Lots of people answered about connecting the keyboard's PS/2 interface direct to the 8051

loke mun seng wrote:
"use VB6 with componet mscomm"

which is about connecting the PC's RS232 COM port to the 8051.

So, mohammad, what do you actually want to do - do you just want to use a PC keyboard on its own (without the PC), or do you want an RS232 serial interface to a PC?