File streams have error flags: fail() for read/write errors, bad() for serious errors (like disk failure), eof() for end-of-file. Check these to diagnose problems instead of guessing.
After an error, the stream stops working until you call clear(). Example: file.clear(); resets error flags so you can retry or seek to a different position. Always check operations: if(!(file >> data)) { handle error; }.
Silent failures leave variables unchanged with garbage values from previous reads. Programs that skip checks produce mysterious bugs.