Символьные строки и функции над ними

Определение: int strncmp(s1,s2, n)
char *s1, *s2;
int n;

#include <string.h>
#include <stdio.h>
#include <conio.h>
int  main(void)
{
	char *buf1 = "aaabbb", *buf2 = "bbbccc", *buf3 = "ccc";
	int ptr;
	clrscr();
	ptr = strncmp(buf2,buf1,3);
	if (ptr > 0)
		printf("buffer 2 is greater than buffer 1\n");
	else
		printf("buffer 2 is less than buffer 1\n");

	ptr = strncmp(buf2,buf3,3);
	if (ptr > 0)
		printf("buffer 2 is greater than buffer 3\n");
	else
		printf("buffer 2 is less than buffer 3\n");
	getch();
	return(0);
}

Определение: char *strcpy(s1,s2)
char *s1, *s2;

#include <stdio.h>
#include <string.h>
#include <conio.h>
int main(void)
{
clrscr();
	char string[10];
	char *str1 = "abcdefghi";

	strcpy(string, str1);
	printf("%s\n", string);
	getch();
	return 0;
}

Определение: char *strncpy(s1,s2,n)
char *s1, *s2;
int   n;

#include <stdio.h>
#include <string.h>
#include <conio.h>
int main(void)
{
	clrscr();
	char string[10];
	char *str1 = "abcdefghi";
	strncpy(string, str1, 3);
	string[3] = '\0';
	printf("%s\n", string);
	getch();
	return 0;
}

Определение: int strlen(s)
char *s;

#include <stdio.h>
#include <string.h>
#include <conio.h>
int main(void)
{
	clrscr();
	char *string = "Borland International";
	printf("%d\n", strlen(string));
	getch();
	return 0;
}

Определение:
char *strchr(s,n)
char *s;
int n;

#include <string.h>
#include <stdio.h>
#include <conio.h>
int main(void)
{
clrscr();
	char string[20];
	char *ptr, c = 'r';
	strcpy(string, "This is a string");
	ptr = strchr(string, c);
	if (ptr)
 	 printf("The character %c is at position: %d\n", c, ptr);
	else
	 printf("The character was not found\n");
	 getch();
	return 0;
}