try yourself |run program

#include <stdio.h> 
#include <conio.h> 
void main(){ 
 int a; 
 int b; 
 clrscr(); 
 printf("Enter value of a: "); 
 scanf("%d",&a); 
 b = a--;
 printf("\n value of b = %d",b);
 printf("\n value of a = %d",a);
 getch();
}

Program Output

Enter value of a: 10
value of b = 10 
value of a = 9