if we use the diff command which finds differences in the two files specified at the command prompt for example take a file named "text"
which has the contents the following:->

" this is a test file"

and other file named "exam" which has the following contents:->

"this is a exam file"
then we execute the command at the shell prompt : diff test exam
then we have the following result on the screen
1c1
< this is a test file
---
> this is a exam file


i want to ask is that what does 1c1 stands for?

thanks in advance