I was looking back at some older class assignments and for one the user had to provide a text file which would be encoded according to an encryption key the user also gave. I essentially solved the problem by placing the content of the text file within a string, retrieving each letter from the string and encrypting it, and then printing the encrypted character back into the same text file. The problem is my professor docked 5% for storing the whole file content within a string, writing something like: "What if the file contents were very large?" I even recall the few people I talked to after the project was graded saying they lost points for the same reason.
At the time I thought he made sense and was too overburdened by my workload so didn't bother seeing if I could fix it because it seemed to be reasonable and simple enough. However now I can't understand how one would be able to edit the text file directly or write on the same file without storing the entire string (because one would otherwise lose its content). How would someone even go about this? Thank you!
Edit: whomever marked my thread as a duplicate to the one above clearly did not understand my question. I am asking how to manipulate the same file without using an absurd amount of memory as the solution I stated would. The other thread clearly asks what the quickest way to read from a file is, which is not at all the same thing. Joop had the right idea of what I meant so I'll try just that, thank you Joop.
