c - What happens to memory after free()?

Question

I know that on your hard drive, if you delete a file, the data is not (instantly) gone. The data is still there until it is overwritten. I was wondering if a similar concept existed in memory. Say I allocate 256 bytes for a string, is that string still floating in memory somewhere after I free() it until it is overwritten?

Answer 1

Your analogy is correct. The data in memory doesn't disappear or anything like that; the values may indeed still be there after a free(), though attempting to read from freed memory is undefined behaviour.