Why the output is different when we add 'int' tag twice in a program when using 'for' loop?

Question

I am a learner and new to C language. While I was creating a function which will give power of two numbers using for loop I encounter that using int declaration before loop

Answer 1

for (k = 1; k <= y; k++)
{
   int r = r * x;
}

int r inside of the for loop declares a separate and unique variable which only is visible in the scope of the for loop.

This r doesn't refer to the r outside of the for loop.

But inside of the initialization part of the loop's (inner) r, the inner r doesn't shadow the outer r because the declaration of the inner r isn't fulfilled at this moment of time.

So, the r in r * x refers to the outer r, not the inner one.

Had you wrote:

for (k = 1; k <= y; k++)
{
   int r = 2; 
   r = r * x;
}

then all r's would refer to the inner r and would completely shadow the outer one.

---

Thereafter, When you use

printf("Power is %d", r);

it prints the value for the outer r variable, which remains unchanged. This is proven with the output of

Power is 1

---

Side Note:

• It doesn't really much sense to declare variables inside of loop's body as you instruct to declare a new variable at each iteration. A compiler can optimize this to only one definition, but better place declarations inside of the initialization part of the for loop or declare them before the loop.