Hi, I'm trying to write a program for homework in my 2nd semester computer science class. What I need to do is update a master file with information based on a transaction file ( both are already created). i.e. from the transaction file I read in Lena 10 and I find Lena 30 in the master file, then I would update the master file with Lena 40. I thought the easiest way to do this would be to read the master list into an array of structures, and compare the transaction entry to each element. Problem is, I don't know if this is possible / how to do it. Any help would be appreciated.

Problem is, I don't know if this is possible

It is possible.

how to do it

Depends on the language you use.
If using C search for examples on using fread, fopen
If using C++ search for examples in fstream, std::istream.