Question

C Programming

Can someone please explain me while the following (c) code prints out 6?

for (i=1; x<=5; i++);

printf ("%d",i);

i=1 initializes the the loop, it is being tested whether it is <= 5 or not. This statement is true, so it goes into the loop and prints 1.

After that, i++, means 1+1=2, i=2. This statement is being tested and it is true, we go into the loop and print 2.

Then i=3, true, loop prints 3 --> i=4, true, loop prints 4 --> i=5, true, loop prints 5 ---> i=6, false, no loop, don't print 6??!!

I have tried and changed the testing condition into i==0, and it still prints 1. Why would it do that? The Expression i=1 is not true?

Thanks

Answer 1

Please notice the semicolon ';' after the for loop.

This means that the statement "printf ("%d",i);" is not a part of the body of the for loop.

Instead this statement is executed when the for loop execution is over.

Let us see how the for loop executes.

Iteration 1: i = 1. Clearly, 1 <= 5 is true, hence increment i to 2

Iteration 1: i = 2. Clearly, 2 <= 5 is true, hence increment i to 3

Iteration 1: i = 3. Clearly, 3 <= 5 is true, hence increment i to 4

Iteration 1: i = 4. Clearly, 4 <= 5 is true, hence increment i to 5

Iteration 1: i = 5. Clearly, 5 <= 5 is true, hence increment i to 6

Iteration 1: i = 6. Clearly, 6 <= 5 is false, hence exit the loop

Hence, after the loop exits, the value of i is 6.

Therefore, printf ("%d",i) outputs 6.