I’m trying to code a program that identifies whether a card is amex visa or mastercard (for harvards free online cs50 course full task here). The code works for amex and mastercard but everytime i test with a 16 digit visa card it prints
<code>VISA
INVALID
</code>
<code>VISA
INVALID
</code>
VISA
INVALID
When it should only print
<code>VISA
</code>
<code>VISA
</code>
VISA
Here is the section of code I presume the problem to be but I can’t see why it’s not working correctly.
<code>while (999999999999999 < card && card < 10000000000000000) // while card is 16 digits
{
card = card / 100000000000000;
if (39 < card && card < 50) // first digit is 4
{
printf("VISAn");
}
else
{
if (50 < card && card < 56) // first 2 digits are 51,52,53,54or55
{
printf("MASTERCARDn");
}
else
{
printf ("INVALIDn");
}
}
}
</code>
<code>while (999999999999999 < card && card < 10000000000000000) // while card is 16 digits
{
card = card / 100000000000000;
if (39 < card && card < 50) // first digit is 4
{
printf("VISAn");
}
else
{
if (50 < card && card < 56) // first 2 digits are 51,52,53,54or55
{
printf("MASTERCARDn");
}
else
{
printf ("INVALIDn");
}
}
}
</code>
while (999999999999999 < card && card < 10000000000000000) // while card is 16 digits
{
card = card / 100000000000000;
if (39 < card && card < 50) // first digit is 4
{
printf("VISAn");
}
else
{
if (50 < card && card < 56) // first 2 digits are 51,52,53,54or55
{
printf("MASTERCARDn");
}
else
{
printf ("INVALIDn");
}
}
}
Any help would be greatly appreciated.
I’ve tried coding individual functions for every major step in my main code so let me know if there is not enough information to go off.
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