MEMSET function and MEMCPY function and FLUSH function

MEMSET - It fill the memory with a constant byte
#include <string.h>
void *memset (void *s , int c , size_t n);

The memset () function fills the first n bytes of the memory area pointed to by s with the constant byte c.

--It return a pinter to the memory area s.
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MEMCPY-- copy memory area

#include <string.h>
void *memcpy( void *dest, const void *src , size_t n);

The memcpy() function copies n bytes from memory area src to memory area dest. the memory areas shoul not overlap. Use memmove if memory areas do overlap.
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SYNC-- flush file system buffers
sync();

Force changed blocks to disk, update the super block.

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FFLUSH-- flush a stream

#include <stdio.h>
int fflush (FILE *stream );

Description: It forces a write of all user-space buffered data for the given output or update stream via the stream's underlying write function.