Actually, I cannot understand.. Why the output is 12?

Question

int f=1,i=2
while(++i<5) {
f*=i;
}
cout<<f;

//output=12

Answer 1

so f=1,i=2
while(++i<5)//here i becomes 3
{
f*=i; //f=f*i; i.e f=1*3=3
}

Now in next iteration i becomes 4 and
f*=i;
So 4*3=12

Next iteration i becomes 5 and loop stops execution as condition is false

Answer 2

First iteration
i = 2, f = 1

while(++i < 5) -----> while(3 < 5) True
f *= i ---> 1 *= 3
f = 3

Second iteration
i = 3, f = 3

while(++i < 5) -----> while(4 < 5) True
f *= i ---> 3 *= 4
f = 12

Third iteration
i = 2, f = 1

while(++i < 5) -----> while(5 < 5) False

Loop terminates, final value of f = 12

Answer 3

You had a greater than symbol inside while and I tried to point it out, so atleast address it so that others would not think what I mentioned earlier is irrelevant.

Answer 4

Is your question right?
Is that "<" or ">"

Answer 5

first entry to the loop before f*=i,
because of ++i.
i = 3 and f =1
so f*=i ; is equivalent to f = 3 *1
f = 3
second iteration before f*=i,
i = 4 and f = 3
f*=i; is equivalent to f = 3 *4
f = 12
i < 5 becomes false and exists the loop. leaving f = 12.
when you don't understand something like that
plug in a "cout" to print the values and watch their changes.
i. e
add this before f*=i ;
cout << i << " * " << f << endl ;
it's a cheap way to debug but it works on small code 😄