Hi Maria Hussain,
A good frequency counter can be found at
http://members.aol.com/cpu8052/wtlcdctr.gif.
It can measure up to 50 MHz. The results are displayed on
a LCD. The hex file can be found at this address
http://members.aol.com/cpu8052/wtlcdctr.hex.
The down side to this counter is it uses a PIC 16F84 IC.
Regards,
Charles Bannister