As a special mobile operating system, iOS was developed and firstly launched on January 9, 2007 by Apple Inc. Although iOS was originally designed to be used in iPhone, it has been also successively applied to iPod touch, iPad, Apple TV, and so on Apple products. Similar to Mac OS X, iOS is based on Darwin, so it also belongs to the Unix-like commercial operating system. As an outstanding operating system, iOS has many merits, such as simple and easy interfaces, amazing functions and excellent stability. Because of that, iOS has become a strong foundation for iPhone, iPad and iPod touch. The numerous built-in technologies and functions of iOS make Apple devices always maintain the lead position that other operating systems can’t compete with. What makes iOS so wonderful? In fact, one of the biggest differences between iOS and other mobile operating systems lies in development language.
The development language of iOS: Objective-C C language is a general and procedural programming language. Therefore, C language compiler exists in a variety of different operating systems. Although C language is widely used in the development of systems and applications, it is not the development language of iOS. As a computer programming language, C + + has also been used widely in the development process, but it is still not the development language of iOS. Objective-C, also known as ObjC, Objective C or Obj-C, is an object-oriented programming language used as the extension of C. Now, we’d like to give readers a brief introduction to the development process of Objective-C – the development language of iOS.
In the early 1980s, Brad Cox and Tom Love invented Objective-C, which is based on a language called SmallTalk-80 in their company StepStone. Created on the basis of C language, Objective-C is a new programming language which has the ability to create and manipulate objects. In 1988, Objective-C language was authorized to NEXT Computer Company who has developed the Objective-C language library and a development environment named NEXTSTEP afterwards. In 1992, the Free Software Foundation’s GNU development environment added support
for Objective-C. In 1994, NeXT Computer Company and Sun Microsystem jointly issued a standard model for NEXTSTEP system and it has been called OPENSTEP, whose implementation name in Free Software Foundation is GNUstep. On December 20, 1996, Apple announced the acquisition of NeXT Software Company. Then, NEXTSTEP/OPENSTEP environment becomes the basis of OS X, which is a major release of Apple’s operating systems. Apple calls the version of this development environment Cocoa.
As the development language of iOS, Objective-C is a very “practical” language. It uses a very small run-time library which is written by C to achieve small increase in applications. In Smalltalk system, even just the opening of a window needs a lot of capacity. But luckily, the procedures written by Objective-C are usually not bigger than their source codes and libraries. Due to its dynamic characteristics, Objective-C doesn’t allow inlining optimization for method, making Objective-C applications generally similar than C or C + + applications.