How is free implemented in C language?

In C, the free function is used to deallocate memory that was previously allocated with functions like malloc, calloc, or realloc. It takes a pointer as an argument and releases the associated memory block back to the system, making it available for future allocations. After calling free, the pointer is no longer valid, and using it can lead to undefined behavior. It's important to ensure that you only free pointers that were previously allocated and not pointers that are NULL or pointing to stack memory.