Error: use of undeclared identifier on an apparently declared variable [duplicate]-CodePudding

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

int main(void)
{
    long creditcardno;
    do
    {
        creditcardno = get_long("enter");
    }
    while (creditcardno<1000000000000 || 
           creditcardno > 9999999999999999);

}


int i = 0;
long cc = creditcardno;
while (cc>0);
{
    cc = creditcardno/10;
    i  ;
}

In the above program in C, I intend to have a variable named cc of long type which will initialize with the value of entered creditcardno by the user.

Getting error message:

credit.c:14:11: error: use of undeclared identifier 'creditcardno' By "undeclared identifier," clang means you've used a name creditcardno on line 14 of credit.c which hasn't been defined. If you mean to use creditcardno as a variable, make sure to declare it by specifying its type, and check that the variable name is spelled correctly.

To my understanding, I have defined variable creditcardno as this variable stores input value of credit card from the user.

CodePudding user response：

You write this part of code outside of main(). That's why it shows an error.

int i = 0;
long cc = creditcardno;
while (cc>0);
{
    cc = creditcardno/10;
    i  ;
}

creditcardno is a variable inside the main scoope. That's why it is only accessible from the main scoope.