c++ for loop help

[boogieman063]

i'm writing a simple for loop for extra credit. it is supposed to print to the screen only the even numbers from 2 - 100. this is what i have and it is infinite looping. i'm using dev c++ version 4.0.

#include <iostream.h>
#include <stdlib.h>

int main()
{
int num;

for(num=2;num<=100;num+2)
{
cout << num <<"\n";
}

system("PAUSE");
return 0;
}
help is appreciated,
thanks
sirhc

[TechKnickle]

Try this:

#include <iostream.h>
#include <stdlib.h>

int main()
{
int num;

for(num=2;num<=100;num+=2)
{
cout << num <<"\n";
}

system("PAUSE");
return 0;
}

Did you want it to loop?

Remember in c++ you have to put the += together if you are adding numbers together (proper syntax).

[boogieman063]

no it was not supposed to loop, thanks that was perfect. let me ask you though, why does it have to be +=, it works, but how?

[TechKnickle]

Yeah, sure no problem.

In c++, the '+' (unary) by itself effectively does nothing. Same concept with the '-', but this does something, it doesn't subtract though. It negates your statement (the value entered or computed earlier).

+= is an assignment operator, telling the computer "this needs to be done, so do it now".

Basically.

[lost-and-found]

basically what you had was a temporary statement: add 2 to num and continue. += says: add 2 to num and store the result as num.

[elmers]

"num+=2" means "num=num+2"