Files (text or binary) do not support "insert" or "delete" operations.
It is recommended to instead open the file for reading, open a different file for writing, and to copy everything from the original until you get to the point of changes, make the changes in the output file, and then copy everything appropriate remaining in the input file. Close both files. If necessary, rename the output file to the name of the input file afterwards.
The same recommendation applies to making modifications of exactly the same length in text files: although it is technically possible, few people get it right.
In-place modification of binary files is common but requires experience.
