why my code is not printing out desired output.

Question

I wrote this code in C as a problem set from CS50, problem needed to be solved was to write a programme that can check if a credit card is valid and then if the card is valid identify ether the card is VISA,AMERICAN EXPRESS OR MASTERCARD.
I wrote the algorithim to check if the card number is valid and is printing invalid if the card number is invialid. My problem is that my code doesn't wanna print out the name is card is card number is valid.

here is my code:

#include <cs50.h>
#include <stdio.h>

int main(void)
{
long card;
//prompt the user for card number
do
{
card = get_long("Card no: ");
}
while (card < 0); // card number must always be greater than zero

//count digit starting from second-last then multiply by two
int card1,card2,card3,card4,card5,card6,card7,card8;

card1 = ((card % 100)/10 * 2);
card2 = ((card % 10000)/1000 * 2);
card3 = ((card % 1000000)/100000 * 2);
card4 = ((card % 100000000)/10000000 * 2);
card5 = ((card % 10000000000)/1000000000 * 2);
card6 = ((card % 1000000000000)/100000000000 * 2);
card7 = ((card % 100000000000000)/10000000000000 * 2);
card8 = ((card % 10000000000000000)/1000000000000000 * 2);

card1 = (card1 % 100 / 10) + (card1 % 10);
card2 = (card2 % 100 / 10) + (card2 % 10);
card3 = (card3 % 100 / 10) + (card3 % 10);
card4 = (card4 % 100 / 10) + (card4 % 10);
card5 = (card5 % 100 / 10) + (card5 % 10);
card6 = (card6 % 100 / 10) + (card6 % 10);
card7 = (card7 % 100 / 10) + (card7 % 10);
card8 = (card8 % 100 / 10) + (card8 % 10);

int sum1 = card1 + card2 + card3 + card4 + card5 + card6 + card7 + card8;

//find digits that where not multiplyed by two
int card9,card10,card11,card12,card13,card14,card15,card16;

card9 = (card % 10);
card10 = ((card % 1000)/100);
card11 = ((card % 100000)/10000);
card12 = ((card % 10000000)/1000000);
card13 = ((card % 1000000000)/100000000);
card14 = ((card % 100000000000)/10000000000);
card15 = ((card % 10000000000000)/1000000000000);
card16 = ((card % 1000000000000000)/100000000000000);

int sum2 = card9 + card10 + card11 + card12 + card13

Answer 1

Khulyso Dev®
Please dont post raw code in the description.

Create a new C code in the playground, paste your code in there and then put the link to that code in the description instead. Then people can review the code much easier and help you faster.

Answer 2

Khulyso Dev®
exactly.
its more readable like that and there will also be syntax highlighting. It doesn't necessarily have to compile.

Answer 3

you mean I should first write code on sololearn playground and then share a link, the one I posted above I wrote it using VS code

Answer 4

Khulyso Dev® I think that you will have to revise either your method or else the data types. The maximum long int is 2147483647.

Answer 5

int sum2 = card9 + card10 + card11 + card12 + card13 + card14 + card15 + card16;
int sum3 = sum1 + sum2;

int length = 0;
long visa = card;
long amex = card;
long master = card;

if((sum3 % 10)!= 0)
{
printf("INVALID\n");
return 0;
}

//Differetiate between visa,master and Amex
while (card >0)
{
card = card / 10;
length++;
}

//Identify if its VISA
while (visa >= 0)
{
visa /= 10;
}
if (visa == 4 && (length == 13 || length == 16))
{
printf("VISA\n");
return 0;
}

//identify if its Amex
while (amex >= 10000000000000)
{
amex /= 10000000000000;
}
if (length == 15 && (amex == 34 || amex == 37))
{
printf("AMEX\n");
return 0;
}

//identify if its mastercard
while (master >= 100000000000000)
{
master /= 100000000000000;
}
if (length == 16 && (master == 51 || master == 52 || master == 53 || master == 54 || master == 55))
{
printf("MASTERCARD\n");
return 0;
}
else
printf("INVALID\n");
return 0;
}