First knowledge of the second bullet of C language

List of articles

• • One . Constant
  • Two . character string + Escape character + notes
  • 3、 ... and . Select statement
  • Four . Loop statement
  • 5、 ... and . function
  • 6、 ... and . Array

One . Constant

Constant ： Describe invariant quantities .C Constants in languages are divided into the following categories ： Literal constants const Modified constant variable #define Defined identifier constant Enumeration constants .
1. Literal constants ： 30; 3.14;‘w’ character ;“abc” character string ;
2.const Modified constant variable

const Embellished a No output 20, If there is no const Will output 20, Make variable a Properties with constants
3.#define Defined identifier constant

Output 100 100 define The identifier is defined MAX So you can output
4. Enumeration constants
Can't change

Two . character string + Escape character + notes

character string
int main()
{
//char Character type
//‘a’- character constants
char ch=‘w’; // Alphabet character w Put it in a character variable to define
//“abcdef”;- Called string

//C There is no string type in the language
return 0;
}

How to save strings ？
Put it in the character array
char arr[10] -- Put... In the array 10 Characters ; for example ：char arr[10]=“abcdef” This can store , The premise is that the space given in front is large enough perhaps char arr[]=“abcdef” -- This automatically determines the previous value according to the size of the subsequent string
A... Is hidden at the end of the string ’’
‘’ Flag for the end of the string

The initialization of the arr1 Occupied 7 Space , Initialization arr2 Account for the 6 Space

%s Print out characters

arr1 and arr2 There is memory space before and after the , The output only accounts for a small part
arr1 The output is that because ’’ and arr2 The output of does not ’’, therefore arr2 The output is as shown in the figure , Until I find ’’ Before printing

This is adding ’’ Then you can output the same

Want to run this program , Find the length of this string , If you use this function, you need to add a header file before it #include <string.h>

strlen Get the length of the string So it is 6
The above 7 Is the length of space occupied by this string （size of） Need to be 7

Escape character ： Changed the meaning of the original characters
C An escape character specified in a language

Escape character
// Three letter words ( Early parsers )
) -->]
( -->[

When the path is printed, it must be

For horizontal tabs , amount to tab

Convert octal numbers to decimal numbers , Find the decimal representation of ASCII Value instead of character This is a character in the figure

if C Nested annotations in a language can cause problems therefore C The annotation style of the language does not support nesting
//-C++ The annotation style of
Write comments for your own code when you write code in the future （ Comb your mind 、 Explain complex code ）

3、 ... and . Select statement

if The choice statement of

if…else if if（ Expression is true ） execute if If false, execute else

C The language implements the selected statement ：if…else Switch…

Four . Loop statement

5、 ... and . function

This is the corresponding function in mathematics . and C The corresponding functions in the language are as follows ：
First of all, define a add function , hold int x int y To assign separately to n1 n2

add- Function name x y For function parameters {} In is the function body int Is the return type The above definition can also be changed to

6、 ... and . Array

Originality is not easy. ; I also hope you guys can support ！