Can I make iPhone compatible apps on the ipad

Is it possible to make it compatible

Yes, I made an app for both iPad and iPhone entitled WileD MathFacts.

The main thing is that you need to code everything (and I mean everything even font size) with respect to the WIDTH or HEIGHT.

What is the width and hight

WIDTH is a constant that represents the width of the screen.
HEIGHT is a constant that represents the height of the screen.

So, if you want something to appear in the middle of the screen regardless of device or orientation, you want it a relative value like WIDTH/2, HEIGHT/2, not 512, 380 or whatever.

You want your sprites to be for example 10% of the screen width, so WIDTH/10, rather than 100 pixels wide.

No I was saying what is the width for the iPod screen and hight of it

iPad: 1024x768 pixels

iPhone 3GS (and original iPod Touch): 480x320 pixels

iPhone 4 and iPhone 4S: 960x640 pixels

iPhone 5 (and latest iPod Touch): 1136x640 pixels

But why do you want to know the width and height of the screen? If you want it to run universally, you have to use the WIDTH and HEIGHT constants.

Oh I thought the width was the width of the ipad only so if I made it for the iPhone it will take the width of the ipad and use those numbers

There is a tutorial on making a universal app for Codea here: http://codeatuts.blogspot.com.au/2012/10/tutorial-22-building-universal-app-in.html

It is also worth reading http://codeatuts.blogspot.com.au/2012/11/interlude-13-pixels-vs-points-in-ios.html to understand the difference between pixels and points in iOS.