Calculate the length of a string in C lang.

strlen.c

#include<stdio.h>
/*
Author:nacer salah eddine.
Description:Calculate the length of a string in C lang.
Compile:
gcc strlen.c -std=c99 -Wall -o strlength
*/
size_t size_of_string(const char* str){
    /*
    Put the @(address) of pointer str into the pointer p
    Example:
    str has,str:0040803c
    assign can be done in 2 ways
    1-
    register const char *p = str;
    2-
    register const char *p;
    p = str;
    
    p has,str:0040803c
    */
    register const char *p = str;
    /*
    loop until u reach the end of the string ('\0') 
    increase the value of pointer p during that.
    
    finally return the difference  between p and str
    Example:
    str at first has,str:0040803c
    p at end has,      p:0040804b

    p - str ==(equals) F (in hex)
    F == 15 (DECIMAL)

    Note:To print the value of any pointer here use 
    printf("%p \n",p);
    */
    while(*p){
        p++;
    }
   return (p-str);

}

int main(){

const char *string = "hello bad world\0";
int str_size = size_of_string(string);

printf("%d\n",str_size);

return 0;
}