Is free() zeroing out memory?

Question

Until today I lived in belief that calling free() on memory space releases it for further allocation without any other modifications. Especially, considering th

Answer 1

free() can actually return memory to the operating system and make the process smaller. Usually, all it can do is allow a later call to malloc to reuse the space. In the meantime, the space remains in your program as part of a free-list used internally by malloc.