concise of strlen&strcpy with pointer -K&R

#include <ctype.h>
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include <string.h>
#define OK 0
int mystrlen(char *);
void mystrcpy(char *,char *);
int bitcount(unsigned );
int main(int argc,char **){
char *s="this is for test of strlen and strcpy ";
int len=mystrlen(s);
char * d=(char *)malloc(sizeof(char)*(len+1));//notice here the space you need to allocate is the // length of string and the lastcharacter '\0'
memset(d,0,len*sizeof(char));
mystrcpy(d,s);
printf("the length of %s is%d\r\n",s,len-1);
printf("the source string is \r\n%s\r\n",s);
printf("the destination string is \r\n%s\r\n",d);
getchar();
return OK;
}
int mystrlen(char * s){
assert(s);
char *p = s;
while( *p != '\0'){
p++;
}
return p-s;
}
void mystrcpy(char *d,char *s){ //cryptic of pointer
assert(s);
while(*d++ = *s++)
;
}