well here it is it checks to see if a number is odd or even:

CODE

#include <iostream>  /*you can have it iostream.h as normal but it will give you a non fatal "antiquated" header error*/ using namespace std; /*you need to use this if you dont include the h on the end of the header*/ long value;   /*makes a long variable which can store larger numbers than interger or int*/ int main() { cout<<"enter a number and i will tell you if it is odd or even"<<"\n"; /*prints instructions to the screen and makes a newline with the escape charachter \n*/ do{  /*starts DOing something (farily ovious isnt it?;) */  cin>>value;  /*reads some keyboard input into the long variable value*/  switch (value % 2){ /*takes the value read in and divides it by 2 then returns the "left overs"-- either a 1 or a 0  another name for % is modulous*/   case 0:  /*checks for a condition to be true */   cout<<"its a even number!"<<"\n"; /*outputs to the screen the results and makes a new line*/   break;  /*breaks the switch and goes to while*/   case 1: /*checks for a condition to be true */   cout<<"its an odd number!"<<"\n"; /*outputs to the screen the results and makes a new line*/   break;  /*breaks the switch and goes to while*/ } }while (1 != 2); /*does something while 1 is NOT EQUAL to 2 (this way it goes on forever) you can use a "sentinal value" to make the user be able to break the chain but i dident feel like including that*/ return 0; /*returns 0 to int main() i guess i dunno for sure :-/ */ }

hope this helps someone!

using namespace std; specifies to use the standard namespace. I don't think it has anything to do with leaving the ".h" on or not, as headers with ".h" are usually C headers. Correct me if I'm wrong.

the return 0; returns 0 to windows or whatever called it.

History of <iostream> and <iostream.h>

A correct C++ program should use <iostream>. The file <iostream.h> is provided for backwards compatability with programs written before the C++ standard was completely defined.

Originally namespace was not part of C++ and so the streams were defined in (what we now call) the global namespace. The C++ standard says that <iostream.h> must be provided for backward compatability with these old programs.


When you include <iostream> you place cin,cout etc into the standard namespace. As a consequence to access these values you need to let the compiler know where to look. This can be done in several ways:

1) Add the follwoing to the top of your source.

2) Prefix all objects in the standard namespace with std::.

3) Selectively use the using directive.

PS. It is extremly bad manners to add using directives into a header file. It is known as polluting the namespace.

why not use?

it works identicaly to

just runs a bit faster, i admit it's a bit harder to read but it is a great performance enhancer.

Tidied up your code and added comments. I hope you find them usefull.

A quick tip:
To make code look good on a web page remove all <tabs>.

Whitespace is your friend. Use it to help make your program more readable.

actualy it's the compiler / processor which supports the valibles not windows. 16 bit compilers have 2 byte ints, 32 bit compilers have 4 byte ints, and i'd guess that 64 bit compilers have 8 byte ints (havent tested this yet, i dont have a 64 bit processor to test on and even though i can convert my compielr to 64 bit i can't run 64 bit apps yet)

Actually, its the compiler that defines the size of integers.

The compiler usually defaults to the size that is most effeciently implemented by the underlying hardware. But most compiler will allow you to change the size of the integer types by specifing the correct flags.

Thus a processor that only supports 16 bit ints natively can be made to support 64 bit ints. The code generated by the compiler is just a lot more convoluted as it must generate the code to simulate 64 bit addition etc.

For most people (the windows users) (or pentium users) the sizes are:
short 2 bytes
int 4 bytes
long 4 bytes

Of course this will very with hardware.

I like this code. And when you put a number that is too large for the type of interger or a letter(Short, long... not sure which one) the return is (typing an odd or even number):