I don't have an Apple computer, only iPad and Debian computer but I still would like to add a feature to iOS app here. Earlier I found out that I can download Xcode, more here, from Apple Store. Now I cannot find Xcode from Apple Store in iPad. I want to get this one here for iPad so how can I get Xcode for iPad?
You currently cannot install Xcode on an iPad or iPhone, or any device other than a mac running OSX. There have been discussions & questions asked about it before; basically you shouldn't hold your breath.
If you have a mac you can always consider VNC if you want to do work remotely on your iPad, but to me it sounds like you don't have a mac and were hoping the iPad could serve as your development environment.
Xcode is a Mac App, not an iOS App. As such, it doesn't run on the iPad. The program you linked to, http://itunes.apple.com/us/app/xcode/id497799835?mt=12, is in the Mac app store, not the iOS App store.
There might be some confusion because Xcode can be used to develop iOS apps, but it itself is a Mac app only.
As with the other answers, you can't directly because OS X and iOS are different platforms with different restrictions and apps (duh). You can however accomplish what you're attempting to do with an OS X machine running and connected to the Internet in order to compile the builds for your iPad.
This is exactly how the Dringend app works (http://dringend.cc/). It runs on your iPad as a slimmed-down 3rd-party Xcode replacement (it even understands
.xcodeproj files!), and uses Xcode via remote OS X host to do the dirty-work.
I thought I read something somewhere about another start-up working towards a product with the same premise, but provides the OS X build-machines as a paid service— I'll update this if I find their name. Until then, there's always OS X hosting.