C++ Standard Library C++ STL Library

C++ <cstring> - memcpy() Function

The C++ <cstring> memcpy() function is used to copy num characters of memory block pointed to by source to the memory block pointed to by destination. The behavior of the function is undefined if:

  • destination and source overlaps.
  • either destination or source is a null pointer.


void * memcpy ( void * destination, const void * source, size_t num );


destination Specify pointer to the first block of memory where the content is to be copied.
source Specify pointer to the second block of memory to copy from.
num Specify number of characters to copy.
size_t is an unsigned integer type.

Return Value

Returns destination


The example below shows the usage of memcpy() function.

#include <iostream>
#include <cstring>
using namespace std;
int main (){
  char str[50] = "Hello World!";
  char new_str[50];
  //copying 5 characters of memory 
  //blocks str into memory block new_str
  memcpy(new_str, str, 5);

  //displaying the result
  cout<<"new_str contains: "<<new_str;

  return 0;

The output of the above code will be:

new_str contains: Hello

❮ C++ <cstring> Library