if (expression)
it_is_true;
else
it_is_not_true;
Mind the semicolons!
it_is_true and it_is_not_true are two commands, not more or less. Of course, you can leave out else and it_is_not_true; if you have no purpose for them.
expression is an mathematic equation. If the result is not zero, it_is_true will be executed, else it_is_not_true.
The following operators can be used for comparisons: (they will return the right number, zero or not zero)
== | equal |
< | less than |
> | greater than |
<= | less than or equal |
>= | greater than or equal |
!= | not equal |
&& | and |
|| | or |
|
IMPORTANT: NOT ONE '=' BUT TWO!!!!! You won't get an error message if you write only '=' instead, but you program won't work!! (In fact, it's an legal expression, but more on that later) |
Example:
if (a==45)
printf("a is 45.");
else
printf("a is not 45.");
(I know that that isn't meaningful... :-)
If you want more commands in comparisons, you must write them into { and }'s. Example:
if (a!=99)
{
printf("a is not 99.");
e=77;
}
(Note that you must not add a semicolon after the })
OK, that's it for now, I'm working on it... :-)