"Good Programmer's note sharing" the similarities and differences between OBJ-C and C + + from Hello World

<a href= "http://www.goodprogrammer.org/" target= "blank" >ios training </A>------My obj-c language notes, looking forward to communicating with you!  

#import <foundation/foundation.h>int Main (int argc,const char** argv) {  NSLog (@ "Hello obj-c");  return 0;  }

1. header file:

#import can guarantee that the header file is included only once, regardless of how many times the command actually appears in that file (equivalent to the #ifdef #define in C #endif)

　　#import <Foundation/Foundation.h> tell the compiler to view the Foundation.h header file in the Foundation framework

2. Obj-c Style string @:

@ "String" is one of the attributes added by obj-c on standard C, which means that the referenced string should be treated as a nsstring element of the cocoa. (nsstring element "NS" +string).

3, "NS" prefix:

"NS" originates from "NextSTEP" (later renamed to Cocoa); It shows that this function is from cocoa;

Adding a prefix can make the code clearer, readable, and prevent name collisions;

4. NSlog () function:

The printf () output function, similar to C, accepts a string as its first argument, which can contain the format specifier (%s);

"Good Programmer's note sharing" the similarities and differences between OBJ-C and C + + from Hello World