Hi Srikanth,
for the AT89C51 the the chip erase is:
set RST to H
set PSEN to L
set P2.6 to H
set P2.7,P3.6,P3.7 to L
raise /EA to Vpp (Vpp 5 or 12V depending on the device)
pulse /PROG for 10ms to L
this is just an example how to erase a chip.
you can get the entire programming and verification algorithm on the datasheet of the atmel controllers.
Christian