comparision of texts in a file

[saisankalpj]

I Have 2 files. Suppose file1.txt contains

name=ravi rollno=9987
name=sri rollno=9988

file2.txt contains

name=ravi rollno=9987 mobileno=9876543212

Now i want to compare the above 2 files and generate a 3rdfile(file3.txt),which contains entries not present in file2.
So file3 should contain

name=sri rollno=9988

The file3 should not contain 'name=ravi rollno=9987' as a part of it is present
How do i proceed?

[Larz60+]

Please try to write the code, when you get stuck, show what you've done, with any errors (complete and unaltered) and we will be glad to help.