C Evaluation Order Questions

1.void main(){

  int i=4,x;

  x=++i + ++i + ++i;

  printf("%d",x);

}

In ++a, ++ is pre increment operator. In any mathematical expression pre increment operator first increment the variable up to break point then starts assigning the final value to all variable.

Step 1: Increment the variable I up to break point.

Step 2: Start assigning final value 7 to all variable i in the expression.

So, i=7+7+7=21

2.void main(){

  int a=10;

  printf("%d %d %d",a,a++,++a);

} 

In c printf function follows cdecl parameter passing scheme. In this scheme parameter is passed from right to left direction.

So first ++a will pass and value of variable will be a=10 then a++ will pass now value variable will be a=10 and at the end a will pass and value of a will be a=12.