Initialize the variable

Question

I'm wondering why example one of the code doesn't work and example two does. The only change is the repetition of 'float'. The error I get are: unused variable and uninitialized variable. Would just like an explanation so I can fully grasp why it is so. Thank you.

Example one:

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

int main(void)
{
    float c;

    do
    {
        printf("Hi! How much change is owed?\n");
        float c = get_float();
    }

    while (float c < 0); 
}

Example two:

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

int main(void)
{
    float c;

    do
    {
        printf("Hi! How much change is owed?\n");
        c = get_float();
    }

    while (c < 0); 
}

Answer 1

It's pretty straightforward. In the second one, the code uses a single variable called c. No problems.

In the first one, by including float in the while statement, the code is redeclaring the variable c. The first c gets replaced by the second c. At that point, the while statement tries to use the new, second var c. Unfortunately, the value previously assigned no longer exist, generating the uninitialized var error. Since this second c var is not used after this, it also generates the unused var error.

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