Loops and file handling (edited)

Question

my prg creates a .dat file containing the roll no, names and marks of students then I proceed to display them individually based on the roll no the user wants to see. For example roll no:42 Mark
roll no:2 Steven roll no: 177 Lucy.( Entered in any order) The prg only works when the data the user wants is the first roll no. Since the roll nos are not continuous a basic loop doesn't seem to work for me.

Answer 1

I didn't understand your problem. Can you add code here?

Answer 2

Copy to your IDE and try it:
https://code.sololearn.com/clCLGAp5X99L

Answer 3

it's on my laptop. I can't really post it here. can't take pictures too

Answer 4

I'll edit the question