Why is "number" undeclared when I declared it in the function?-CodePudding

#include <stdio.h>

void numberisone()
{
    int number = 1;
}

int main()
{
    numberisone();
    
    printf("%d", number);

    return 0;
}

I'm fairly new to programming so make the explanation as simple as possible :) Thanks in advance!

CodePudding user response：

The scope of the declaration of the variable number is the outermost block of the function numberisone

void numberisone()
{
    int number = 1;
}

Outside the function the variable is not alive and visible.

So the used identifier number in main is undeclared

printf("%d", number);

To make your program more or less meaningful declare the function like

int numberisone( void )
{
    return 1;
}

and in main write

int number = numberisone();

CodePudding user response：

#include <stdio.h>

int numberisone()
{
    int number = 1;
    return number;
}

int main()
{
    int num_1 = 0;
    num_1 = numberisone();

    printf("%d", num_1);

    return 0;
}

CodePudding user response：

Variables declare inside a function have a scope inside that function only that is the variable can be use only inside the function. If you nee you can return the value from the function as like,

 #include <stdio.h>
    
    int numberisone()
    {
        int number = 1;
        return number;
    }
    
    int main()
    {
        printf("%d", numberisone());
        return 0;
    }