cppreference.com > Standard C String and Character > memset memset Syntax:
      #include <string.h>
      void* memset( void* buffer, int ch, size_t count );
The function memset() copies ch into the first count characters of buffer, and returns buffer. memset() is useful for intializing a section of memory to some value. For example, this command:
       memset( the_array, '\0', sizeof(the_array) );
...is a very efficient way to set all values of the_array to zero. The table below compares two different methods for initializing an array of characters: a for-loop versus memset(). As the size of the data being initialized increases, memset() clearly gets the job done much more quickly:
Input size | Initialized with a for-loop | Initialized with memset()
--- | --- | ---
1000 | 0.016 | 0.017
10000 | 0.055 | 0.013
100000 | 0.443 | 0.029
1000000 | 4.337 | 0.291
Related topics: memcmp memcpy memmove