Memory management of C

#include<stdio.h>
#include<stdlib.h>
#include <string.h>

typedef struct 
{
    
	int x;
	int y;
}FTest;

int main() {
    

#if 0



	char p[128];

	strcpy(p,"tom");

	printf("%s \n",p);

	char* ptr = malloc(128*sizeof(char));// Allocate a space on the stack 
	FTest*pName=calloc(10, sizeof(FTest));// Allocate ten memories and all for 0
	printf("%d \n\r", pName[4].x);
	pName=realloc(pName,10+2*sizeof(FTest));// Reassign add two after FTest Size of memory 
	pName[12].x = 10;
	printf("%d \n\r", pName[12].x);
	if (ptr == NULL)
	{
    
		fprintf(strerror," Out of memory ");
		exit(EXIT_FAILURE);
	}
	else
	{
    
		strcpy(ptr,p);
	}
	free(ptr);
#endif // 0

	//memset  and memcpy
	char str[] = "IIII";
	memset(str,'k', strlen(str));// Parameters ： Array of settings , Replace character , Replace the first few 
	printf("%s \r\n", str);

	// Chinese characters one Chinese character takes up two bytes, so copy 3 One can only be copied to half of the second 
	char dest[20] = " Autumn water stretches to the sky ";
	char dest1[20] = {
    0};
	memcpy(dest1, dest,3);// autumn ？
	printf("%s \r\n", dest1);


	system("pause");

}