Everything is fine in this code but when I am choosing choice number 1 it is showing invalid choice I feel so irritate now

Question

#include<stdio.h>
int main(){
int choice,a,b,s;
printf("\n1.addition");
printf("\n2.odd-even");
printf("\n3.printing n numbers");
printf("\n\n enter your choice:");
scanf("%d",&choice);
switch(choice){
case1:
printf("enter two numbers:");
scanf("%d,%d",&a,&b);
s=a+b;
printf("\n sum is %d",s);
break;
case 2:
printf("enter a number:");
scanf("%d",&a);
if(a/2==0){
printf("even number:");
}
else{
printf("odd number:");
}
break;
case 3: printf("enter a number: ");
scanf("%d",&a);
for(b=1; b<=a;b++)
printf("%d",b);
break;
default:
printf("invalid choice:");
break;
}
return 0;
}

Answer 1

Label for case 1 was missing a space. It should be

case 1: // not case1:

To verify <N> is an even number, modulo <N> by 2, and ensure that the result was zero (no remainder from the division operation).

if( a % 2 == 0 ) // not a / 2

Answer 2

This code is hard to read cause it's just text with no indentation. Can you link the code from the Code Playground instead?

Answer 3

Thanx alot