const char *s1 = "ZBCDEF";
const char *s2 = "ABCDEFG";

/* strlen using compact pointer notation
*/
size_t MyStrlen(const char *s1)
{
    const char *ptr = 0;                        
    
    while(*s1)                                    
    {
        *s1++;                                    
        ++ptr;                                    
    }        
                
    return( (size_t)ptr );                     
}

/* String comparison using compact pointer notation
*/
int MyStrcmp(const char *s1, const char *s2)
{    
    while(*s1)                                     
    {
        if (*s1 == *s2)                         
        {
            *s2++;        
            *s1++;
                                                
            if (*s2 == 0 && *s1 == 0)         
                return(0);
            else if (*s2 == 0 && !*s1 == 0)     
                return(1);    
            else if (!*s2 == 0 && *s1 == 0)     
                return(-1);            
        }
        else if(*s1 > *s2)                        
        {
            return(1);
        }
        else if(*s2 > *s1)                        
        {
            return(-1);
        }        
    }
return(0);
}

char *GetSubString(const char source[], int start, int count, char result[])
{
    
    if ((unsigned int)start > strlen(source))         
    {                             
        *result = 0;                                
    }
    else
    {    
    
        if ( (unsigned int)start + count > strlen(source)) count = strlen(source) - start;

        while(start > 0)                        
        {
            source++;
            start--;                                
        }

        *(result + count) = 0;                        
    
        while ( count > 0 || *(source + count) != 0 )         
        {
             count--;             
            *(result + count) = *(source + count);    
        }
    }
    return(result);
}

#define RESULT_MAX 19

int main(void)
{
    char result[19];
    const char source[] = "JIBSON GLOMGOLDS";
        
    printf("nMyStrlen: %inn",(int)MyStrlen(s1));
    printf("MyStrcmp: %inn", MyStrcmp(s1,s2));    
    printf("GetSubString %snn", GetSubString(source,1,5,result));

    return(0);
}