c language applet - custom string copy function

#include

#include "stdlib.h"
#include "stdio.h"
#include "string.h"
//Custom: string copy function, complete string from, to to copy
void copy_str1(char *from, char *to )
{
for (; *from!='\0'; from++, to++)
{
*to = *from;
}
*to = '\0';
}

void copy_str2(char *from, char *to)
{
while(* from!='\0')
{
*to = *from;
from++;
to++;
}
*to = '\0';
}

//++ has high priority, dan is ++ is suffix ++
// so execute first *to = *from; then from++; to ++from++;
void copy_str3(char *from, char *to)
{
while(*from!='\0' )
{
*to ++ = *from ++;
}
*to = '\0';
}

void copy_str4_1(char *from, char *to)
{
while((*to = *from) !='\0')
{
to++;
from++;
}
}
void copy_str4_2(char *from, char *to)
{
while((*to++ = *from++) !='\0')
{
;
}
}

void copy_str5(char *from, char *to)
{
while((*to++ = *from++))
{
;
}
}

void main()
{
char *p = "abcdefg";
//char *p2 = NULL;
char p2[100] ;
copy_str5(p, p2);

//strcpy(p2, "abcdeeg");
printf("p2:%s\n", p2);

system("pause");
}