I am a newbie, while my teacher give me a big problem~

Find a string which is specified in a file. If it exists, print the first place where the string is in, or print there is no such a string.
For example: Find c;\1.txt MyGod!
It will find if there is a string "MyGod!" in the 1.txt, and you can modify this string.

Only use assembly language, and my teacher doesn't let me use win32 assembly language~

please help me~ thank you very much!!!