Control Flow-For Loops

@Rodrigo, great explanation, but I doubt he can understand all the terminology you're using, considering he's having trouble with loops.

To begin, a for loop, while loop, and do-while loop all essentially do the same thing. They repeat the code within their "blocks" if the code passed into it evaluates to be true. Here's an example:

for(  int x = 0; x < 99; x++){
  printf("Hello, can you hear me now?");
}

The for loop goes though those parenthesis like so:

1. Alright, I see an integer, x, is equal to 0. Cool.
2. We want to check to see if x < 99
   • If x is less than 99, that expression will return what is called a boolean value. Boolean values return only two
     values: true, and false. If x checks out to be less than 99, then this value is true.
3. The printf statement is now ran since 0 is obviously less than 99

Now you're thinking, what about the third statement? Well, this isn't executed until after the code is run.

1. Now, the third statement is executed, x++. This is the same as saying x = x + 1. Just a shortcut. So now x is
   equal to the value 1.
2. The loop now kicks back to the top and evaluates the second statement. Now x is equal to one, so we're checking to see if 1 < 99. This is true, so the cycle goes through again.

Why isn't the first statement executed each time the loop runs, setting x = 0 continuously? Well, the for loop is actually a shorthand for the while loop. That first statement is technically treated as if it was declared outside the context of the loop. You can best see this through an example of a while loop:

int x =0;
while( x < 99){
  printf("Hello, can you hear me now?");
x++;
}

This does exactly the same thing as the for loop, but is a little less compact to write.

do-while loops differ in that the code will inside the loop will run at least once regardless of the condition being true or not.

Here's a good for loop syntax:

for( term1 /*variable declaration*/; term1 comparisonOperator term2; incrementOrDecrement){
  //Code to execute
}