User defined atoi()

Userdefined atoi( ) function explained with example:

Program:Sum of Digits of a Number 

#include<stdio.h>

int main(int argc,char *argv[])

{

       int num,sum=0,rem;

      if(argc!=2)

         exit(1);

      for(i=0;argv[1][i]!='\0';i++)// This is your own atoi function

      {

          num=num*10+(argv[1][i]-'0');

       }

printf("The entered Number is %d",num);
// This will display your entered number.

while(num!=0)// Code for determing sum of digits of number

{

    rem=num%10;

    num=num/10;

    sum=sum+rem;

}

printf("Sum of digits of your entered number is %d",sum);

return 0;

}