iOS Development Learning Record the 3rd day of C language learning

(a), Learning iOS Development, we need to be inquisitive, if learning, from where to learn, first iOS is developed by Apple mobile operating system [1]. Apple first unveiled the system at the Macworld Conference on January 9, 2007, originally designed for the iphone, and later applied to products such as ipod Touch, ipad and Apple TV. iOS, like Apple's Mac OS X operating system, belongs to the Unix-like commercial operating system. Unix systems are mostly written in C, so we start with the C language.

1. The history of C language:

The C language was invented in the early 70. In 1978, the C language was formally published by the American Telephone and Telegraph Company (T) Bell Laboratory. At the same time by B.w.kernighan and D.m.ritchit co-authored the famous "The C programming LANGUAGE" a book. Usually referred to as "K&r", some people call it "K&r" standard. However, a complete standard C language was not defined in the K&r, which was later developed by the National Standards Institute (AMERICAN) (standards Institute) on the basis of a C language standard published in 1983. Usually called ANSI C.

2, C language features:

C language Concise, compact, flexible, easy to use. A total of 32 key words

Auto : declaring automatic variables  

Break: Jump out of the current loop

Case: Switch Statement Branch

Char: Declares a character type variable or function return value type

Const: Declaring read-only variables

Continue: End the current loop and start the next cycle

Default: "Other" branch in a switch statement

Do: loop body of a looping statement

Double: declaring a dual-precision floating-point variable or function return value type

ELSE: Conditional statement Negation branch (with IF)

Enum: declaring enum type

extern: Declaring a variable or function is defined in another file or elsewhere in this file  

Float: Declares a floating-point variable or function return value type

For: A looping statement

Goto: Unconditional Jump Statement  

if: Conditional statement  

int: Declaring an integer variable or function

Long: Declares a length integer variable or function return value type

Register: declaring register variable

Return: Subroutine return statement (can take parameters or without parameters)

Short: Declaring a variable or function with a shorter integer

Signed: Declaring a signed type variable or function

sizeof: Calculates the data type or variable length (that is, the number of bytes)

Static: Declaring a static variable

struct: Declaring struct-body type

SWITCH: For switching statements

typedef: Used to alias data types

Unsigned: Declaring an unsigned type variable or function

Union: Declaring a shared body type

void: Declares a function with no return value or no argument, declares an untyped pointer

Volatile: Explanatory variables can be implicitly changed in program execution

While: loop condition of a looping statement

3, C program simple understanding and introduction          

Main ()
{
printf ("The World, Hello! \ n ");
}

Main is the function name of the main function, which means that this is a main function.

Each C source program must have, and only have one main function (main function).
Function call statement, the function of the printf function is to send the contents of the output to the display to display.
The printf function is a system-defined standard function that can be called directly in a program.

iOS Development Learning Record the 3rd day of C language learning