Previously we learn Delegation : iOS Concept : Delegate  

The iOS software Development Kit (SDK) was released in 2008 and enables third-party developers to create and deploy applications to iPhone, iPad and iPod touch devices. The iOS SDK was designed so that it would not only allow application developers already familiar with the Mac OS X platform to migrate their code to run on iOS mobile devices but also provide low barrier for novice developers to create rich interactive applications. For iOS software applications development there are Tools provided to us Objective-C and XCODE to develop native apps for iOS devices, they are described below: 

Objective C:

Objective C is an object-oriented programming language, which is used for developing applications for iOS, it is essentially an additional object-oriented layer with Smalltalk-style messaging on top of the standard C language. Hence, regular C programs can be compiled using an Objective C compiler and many frameworks within iOS also provide C style interfaces. 

Objective C works on the models of message passing where instead of method calls, messages are passed to the target method. 

Objective C also provides run-time support for reflection which allows a program to query and modify its own internal structure and hence, behavior during execution.   An important thing to note about objective C especially for C++ programmers is that Objective C does not support operator overloading and also does not allow multiple inheritance.

XCODE:

Xcode is the Integrated Developer Environment (IDE) of Apple for writing applications for iOS and Mac OS X.Alcatraz is a package manager for Xcode, which allows you to install additional plugins right inside of your IDE.

Xcode comes with a suite of developer tools and comprehensive documentation. It utilizes a modified version of the GNU Compiler Collection (GCC) for compiling Objective C programs and uses the GNU Debugger (GDB) back-end for debugging

Xcode compiles iOS applications to run on ARM-based processors which are used in all the iOS devices.

One of the interesting features of Xcode is that it allows the distribution of compiling and building applications across multiple networked computers, a capability known as Dedicated Network Build.

Next, we will see about : Objective C - Overview