What do these code snippets print? Can you explain its behaviour?

Question

#include <stdio.h>

void proc(void);

int main(){
printf("First start:\n");
proc();
printf("Second start:\n");
proc();
printf("Third start:\n");
proc();
return 0;
}

void proc(void){

static int a;
printf("Variable a = %d\n", a);
a++;
}

Answer 1

You could run this code in Code Playground.

Answer 2

First start:
Variable a = 0
Second start:
Variable a = 1
Third start:
Variable a = 2

static variables only need to be declared once and when declared multiple times, they just refer back to the original one.

So initially you created a with a default value of 0.
Then you post incremented 3 times.

Therefore, your output is 0, followed by a plus one to 1, followed by a plus one to 2, followed by a plus one.