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C language 2022 Shanxi upgraded C language knowledge points

2022-07-21 21:10:00 【Guo Guo's learning journey】

Catalog

One 、 The basic definition

Two 、 Sequential programming

3、 ... and 、 Selection structure

Four 、 Three circulation structures

5、 ... and 、 Array

6、 ... and 、 function

7、 ... and 、 The pointer

8、 ... and 、 Structure 、 Shared body 、 enumeration

Nine 、 file

Ten 、 Preprocessing

One 、 The basic definition

One 、 Concept

1. machine language （ The computer can directly compile and recognize ） link --> Semiotic language （ assembly language ） compile --> High-level language （ compile ）;

2. compiler ： After a compilation, there is no need to recompile [c Language 、c++、java];

3. Interpreter ： Every time, it needs to be reinterpreted [pyhton];

4. Program structure ： Sequential structure 、 Selection structure 、 Loop structure ;

5. The procedures are all based on main（） The function starts executing , There is and only one main function , Then proceed from top to bottom （ When encountering a cycle, do a cycle , When you meet a choice, make a choice , When you encounter a function, do a function ）;

6. The data of the computer is stored in binary form in the computer ;

7.C Keywords of language (auto break case char const continue default do)

①. Data type key : char double enum float int long short signed struct union unsigned void

②. Control statement keywords : for do while break continue return if else goto switch case default

③. Storage type key : auto extern register static

④. Other keywords : const// Declare read-only variable sizeof typedef volatile// Variables can be changed implicitly in the execution program

Two 、 Often test concepts

1. Preprocessing #define PI 3.14 No c Part of the language , No running time , Without a semicolon ,c A program compiled in a language is called a source program , It uses ASCII The code is stored in a text file ;//#define PI 3.14; This writing is wrong , Semicolons should not appear in preprocessing

2. Every c In language programs main There is and only one function ;

3. Functions can be called nested, but not defined nested ;

4. The implicit storage type for variables is auto;

5. The implicit storage type of the function is extern： Expand the scope ;

6. The main function can be divided into two parts ： Function description part and main function body ;

Any non main function can call any other non main function ;

（ A function that directly or indirectly calls the function itself is called a recursive call of a function ）

7.c The steps and methods of language execution ：.c[ Source program ]--- compile --->.obj[ Target file ]--- Connect --->.exe[ Executable file ];

（.c--->.obj--->.exe）//.c and .obj Files can't run ,.exe Before running, compile , Back connection , Last run ;

8.c A program written in is called a source file , Also known as compilation unit ;

9. If a statement has only one semicolon ; This statement is empty ;

10. identifier ：

（1） Must consist of alphanumeric underscores , The beginning can only be letters or underscores ;

（2） Identifiers are divided into keywords 、 Predefined identifiers 、 User identifier ;

（3） Keywords cannot be used as user identifiers （ Identifiers defined by users themselves are called user identifiers ）;

（4）main、define、scanf、printf None of them are keywords （！！！）;

（5） Confuse If Can be used as an identifier （ because if The initials are capitalized , So it's not keywords ）;

（6） Predefined identifiers are define、scanf 、printf、include;

（7） Predefined identifiers can be used as user identifiers ;

11. The difference between a statement and an expression is whether there is a semicolon , Statements have semicolons , The expression doesn't have ;

12. The operand of an expression can be a constant 、 Function call 、 Variable ;

13.c The basic unit of a program is a function ;

3、 ... and 、 Algorithm

1. Characteristics of the algorithm ： Fineness 、 deterministic 、 effectiveness 、 There is one or more outputs , Zero or more inputs ;

2. How to describe an algorithm ？

Express the algorithm in natural language 、

Use the program flow chart to represent the algorithm 、

S The flowchart represents the algorithm 、

Using pseudocode to represent algorithm 、

Express algorithm in computer language ;

3. Algorithm ： No input , But there must be output ;

Four 、 Hexadecimal conversion

1. All hexadecimal conversions are converted to binary and then to other hexadecimal ;

2. Octal to binary according to 3 Bit calculation , 16 bits to binary according to 4 Bit calculation ;

3.c There are only eight in the language 、 Ten 、 Hexadecimal , No binary . But when it's running , All the bases must be converted to binary for processing .

4. Regulations

A.c The language stipulates that octal should start with 0 start .018 It's illegal. , Octal No Yes 8 Meet 8 Into the 1;

B .c The language stipulates that hexadecimal should start with 0x start , Output lowercase %x, Output uppercase %X;

Two 、 Sequential programming

One 、 Constant

1. Integer constant ：

134（ Decimal number ）、 034（ Octal number ）、 0XA2（ Hexadecimal number ）、

45L（ Long plastic surgery ）、 7UL（ Unsigned long shaping ）、8U（ Unsigned shaping ）

U representative unsigned L representative long

Real constant ：

1.3（double type ）、 1.5f、1.5F（float type ）、

1.4e3（ The index means ）、1.4E-3（ Capitalizable ）;

float Effective precision 6 position double Effective precision 15 position ;

a. 2.333e-1 It's legal , And the data is 2.333*10 Primary

b. Test formula ：e front e There must be a few in the future ,e Must be an integer after

3. character constants ：‘a’（ character a）、 ‘\n’（ Escape character ）、 ‘\101’（\ Followed by octal numbers ）、 ‘\x46’（\x Followed by hexadecimal ） example ：‘\n’ ‘\t’ ‘\\’ ‘\’ ‘\0’;

Possible mistakes in the exam ：

a. The wrong form of a single character ：‘65’“1”;

B. Characters can be used for arithmetic operators ：‘0’- 0 = 48;

c. How to convert upper and lower case letters ：‘a’- 32 = ‘A’;

d.‘a’ Of ASCII Code for 97,‘A’ Of ASCII Code for 65,‘0’ Of ASCII Code for 48‘ ’（ Space ） Of ASCII Code for 32‘\0’ Of ASCII Code for 0;

e.‘z’-‘a’= 25;// The difference between letters 25 position ;

4. String constant ：

“abcde” Hide a behind ‘\0’;

example ：strlen(“abcde”)=5;

sizeof(“abcde”)=6;

strlen(“abcde\0abcde”)=5 //strlen encounter \0 end

sizeof(“abcde\0abcde”)=12;

strlen(“a\nb\t\101dc”)=7 a \n b \t \101 d c =7;

5. Symbolic constant #define PI 3.14 // Remember that there is no semicolon after pretreatment

（1） The definition of constants can also be used const Definition for example ：const int a;// Defined a constant a Constant a Will open up space ;

（2） The value of a constant cannot be changed ;

Two 、 Variable ：

Define before use .// The purpose of defining variables ： Make room for variables in memory .

（1）int (4Byte) short=(short int)(2Byte) long(long int)(4Byte)

char(1Byte) float(4Byte) double (8Byte)

1.. Reference type （ Derived type ）

Array ：（ An array type * Number for example int a[10]=int *10=（40Byte））

The pointer ：（ stay 64 In a bit computer 8Byte,32 Bit computers account for 4Byte）

Structure ：（struct） Separate space for each byte ;

Shared body ：（union） Shared memory space , Total memory opened by the largest member ;

2.. Function type

（1） Enumeration type （enum）： Limited plastic surgery

（2）void Empty type

（3） Unsigned type ：unsigned

example ：

（1）unsiged long int a=10;// Unsigned long

（2）unsiged b=10;// Unsigned shaping

（3）unsiged int c=10;// Unsigned shaping

（4）unsiged long d=10;// Unsigned long shaping

3. Assignment operator 、 Arithmetic operator 、 Relational operator 、 Logical operators

The remainder operator %

Be careful ：% The left and right sides must be integers , The divisor is negative Whether the divisor is positive or negative , The results are all negative

example ： -17%3=-2 17%3 =2 17%-3=2 -17%-3=-2

357%10=7 357/10=35 357/10%10=5

Arithmetic expressions ：+ 、 - 、* 、/

Be sure to pay attention during the exam 3/2=1;
3.0/2=1.5

Assignment compound expression

int a=2;

a*=2+3// Equivalence and a=a*(2+3)

Be sure to pay attention to , In the first 2+3 Put parentheses on ,（2+3） recompute ;

++、- - expression （ Self adding and self subtracting expression ）

formula ：++ Add before use ,++ First use later +（ Subtraction is the same thing ）

Comma expression

‘ ,’ The lowest priority , Output the value after the last comma

example ：

printf（“%d”,1,2,3）;// The output is 3;

z=（2,3,4）// The whole assignment expression z The received value is 4;

z=2,3,4// The whole thing is a comma expression z The received value is 2;

Logical operators

Logical expression ：&&（ And ）、||（ or ）、！（ Not ）

！> && >||（ Priority level ）

c True use and non use in language 0 To express , False use 0 To express ;// Not 0 It can be expressed as an integer 、 decimal ;

For relational operators ： The result represented by logical operators ：1 It's true ,0 For false ;

stay c Execute expressions in language a&&b, If && False before ,&& Do not execute after , If && The former is the real talent, and the latter ;

stay c Execute expressions in language a||b, If || The former is true ,|| Do not execute after , If || The former is false before the latter ;

notes ： Empty statements cannot be executed at will , Will lead to logical errors ;

The note is not c Language , No running time , There's no semicolon , You can't nest ！

Conversion between different types

int+int=int char+int=int

As long as there are floating-point types involved in the operation , All for double type

Cast

example （int）（（double）（7/2）+3.5） The value of is 6

Calculate first 7/2=3 3+3.5=6.5 transformation int=6

4. Standard type input and output

printf（“a=%d\nb=%d”,1,2）;// The result is a=1

b=2

Standard input and output types ：（ Positive and negative can refer to the number axis , Left minus right positive ）

%d（ Shaping input and output decimal numbers ）、

%3d（ The input and output occupy three spaces on the right ）、

%-3d（ The input and output occupy three spaces on the left ）、

%c（ Input and output characters ）、

%s（ Input and output string Just need the first element address ）、

%e（ Input output exponential form ）、

%o（ Input output octal ）、

%x（ Input / output hex ）、

%u（ I / O unsigned form ）、

%f（ I / O floating point ）、

%lf（ Input double Type use ）、

%hd ( Output shaping ）、

%p （ Output address format ）、

%10.5f（ Proportion of output 10 grid The decimal point is one place Keep the precision of five decimal places Four Round to the right ）、

%-10.5f（ Proportion of output 10 grid The decimal point is one place Keep the precision of five decimal places Round to the left ）;

%%（ Output one %）、

%#o（ Octal with leading ）、

%#x（ Hexadecimal with leading ）;

Be careful ： At the time of input , Input in strict accordance with the input format

example ：scanf（“a=%d”,&a）;// When inputting, you need to input a=1;

In this way, we can assign a value to a;

When inputting real data ,float According to %f Input ,double According to %lf Input ;

When there is a definition int a,b;

scanf（“%3d%d,&a,&b）;// Input 12345 123 The received a=123,b=45;

scanf（“%d%3d,&a,&b）;// Input 12345 123 The received a=12345,b=123;

notes ：char s[30],s2[30];

Use scanf（“%s %s”,s,s1）;// Spaces must be used between , Do not use other characters ;

Common output functions ：

getchar()、// Receive input of one character ;

putchar( )、// Output a character ;

gets()、// Enter a string ;

puts();// Output a string ;

How to put two variables a,b The value of the swap ？a=t;a=b;b=t;

a=a^b;b=a^b;a=a^b; Bitwise XOR ;// To eight bit binary operation

How to put two variables a,b Sort from small to large or from small to large , This formula has generalization significance ！

3、 ... and 、 Selection structure

if...else...

1. about if...else if...else... Only the conditions that are satisfied first can be selected to execute , Others are not implemented ,else Always closest to him if Connected to a ;

notes ：if（a>5）;// This sentence is empty , There is only one semicolon ;

Pay attention to differences ：

if（a>b）t=a;a=b;b=t;
if（a>b）{t=a;a=b;b=t;}

These two sentences mean different things , Pay attention to distinguish ,if If there is no {}, Then his executive sentence can only be followed by his first sentence ; end

// therefore , In programming or problem solving , Be sure to see if The scope of the statement ;

Conditional expression （c The only ternary operator in the language ）

The general form is ：（ expression 1）？ expression 2： expression 3;

The execution direction is from right to left ;

formula ： Before the truth and after the falsehood ;

stay C In language , result 1 and result 2 Must be of the same type

example

switch sentence

First of all, we should clarify his format

The process of execution must be understood ;
Yes no break The difference between ：

No, ： As long as there is one case To satisfy the , From case Start and continue
Yes ： encounter break Just jumped out switch sentence ;

break stay c Language is breaking up , make a clean break with ;

switch Only with break Use it together ,continue Can not be ;
Since everyone knows switch The nature of , Then let's do a problem

Is this correct ？

The answer is right ,continue It's for the circulatory body , about switch No effect

And the output result is 1*3*5*

switch It is a compulsory exam every year , Be sure to use skilled

Four 、 Three circulation structures

while loop :while（ The loop condition ）{ The loop body ;}
do while loop ：do{ The loop body }while（ The loop condition ;）;// Remember that there is a semicolon at the end
for loop ：for（ initial value ; The loop condition ; Cycle increment ）{ The loop body ;}

The concept of circulation

1.while Circulation and do while Difference between cycles ：do while Will unconditionally cycle once and then judge ;

2.for There are two semicolons in the loop ;

3. When writing programs, you must pay attention to writing cycle conditions , Otherwise, it will become an endless cycle ;

3、 ... and 、break And continue The difference between

1.break：break It means to break , Destroy the whole cycle , So I met break Just jump out of this layer ;

2.continue：continue It means to continue , But to end this cycle , The remaining statements in the loop body are no longer executed , Jump to the beginning of the cycle , Then judge the conditions , Continue to cycle ;

5、 ... and 、 Array

One 、 The concept of array

1. Basic concept of array ： A continuously stored collection , All element types must be the same

[ Basic data type 、 Structure ];

give an example ：struct Stu{....};struct Stu a[10];

int a[10];

Only constants or expressions can be used to define the number of arrays , It can't be a variable ;

for example int a[10];

int a[5+5];

#define N 5 int a[N+4];

int n=10; int a[n];// Wrong definition of array method

Two 、 One dimensional array

1. Definition ： data type Array name [ Constant expression ];//auto int a[10];

2.struct Stu{....};struct Stu a[10];// Array a Every element is Stu Type of

a Is the address of the first element of the array ;10 Represents the number of array elements ; Every element in the array In memory They are stored continuously ;

Initialization of one-dimensional array and use of array ：4 In the form of .

int a[10]={...};// Initialize the value for each element of the array
int a[10]={0};// All elements of the array are initialized to 0
int a[10];a[0]=1;// Assign initial values to one or more elements of the array , The other elements are uncertain values
int a[10]={1,2};// Assign initial values to one or more elements of the array , The rest of the elements are 0

Be careful ：int a[5]={1,2,3,4,5,6}; It's wrong. , The subscript crossing the line ;

Two dimensional array

int a[3][4]; Altogether 3*4（12） Elements , Every element is int Type of , The array name is the address of the first element of the array ; This array has three rows and four columns ;
Each element of a two-dimensional array is stored continuously in memory by row ;
Initialization of 2D array ：

int a[3][4]={...};// Initialize the value for each element of the array
int a[3][4]={1,2};// Assign initial values to one or more elements of the array , The rest of the elements are 0
int a[3][4]={0};// All elements of the array are initialized to 0
int a[3][4];a[0][0]=1;// Assign initial values to one or more elements of the array , The other elements are uncertain values
int a[][4]={...};// Assign initial values to each element of the array , Omit the number of lines

A character array

Array of strings

（1） The way of string input and output ：

Input gets（）;// You can receive any string with a space in the middle

scanf（）;// Cannot receive strings with spaces in the middle. Use spaces as spacers

Output

puts（）;

printf（）;

2. Two dimensional array of strings

char a[4][10]={"aaaa","bbbb","cccc","dddd"};// Every line in the array is a string

Character array common functions

From header file #include<stdio.h>

a=getchar();// Receive a character on the keyboard and assign it to a

putchar(a);// Output a Stored characters

gets();// Receive a string

puts();// Output a string

#include<string.h>// Remember to add header before use

strcat( character string 1, character string 2);// take 2 Connect to 1 after

strcpy( character string 1, character string 2);// take 2 Copy to 1

strcmp( character string 1, character string 2);// Compare 1 and 2 Size ,

Such as a string 1> character string 2 Returns a positive integer ,

character string 1== character string 2 return 0,

character string 1< character string 2, Returns a negative integer ;

strlen(a);// A character array a The length of （ barring ‘\0’）;

sizeof(a);// Need header file #include<stdio.h>, Array a Occupied memory space ;

strlwr(a);// Turn all uppercase letters in the character array into lowercase ;

strupr(a);// Turn all lowercase letters in the character array into uppercase ;

6、 ... and 、 function

The concept of function

A function represents a function module , yes c The basic unit of language ;
One c A program is made up of one or more program modules , Each program module acts as a source file ; A source file is composed of one or more functions and other contents .
All functions are parallel , Mutually independent ;
Functions are divided into library functions （string.h or math.h） And user defined functions ;
The form of function is divided into nonparametric function and parametric function ;

Calling procedure of function

The formal parameter variable specified in the definition function , When there is no function call , They do not occupy storage , Only when a function call occurs , Only the formal parameters in the function are allocated to the memory unit ;

Argument and formal parameter passing ：

When all variables ： Single value transmission ;
When all are arrays ： One way address delivery ;

If the function has return sentence , You can use the return Bring the function value back to the main function ;
After call , The formal parameter unit will be released ;

notes ： When defining a function with a return value , We should avoid the following situation ：

！！！ When a<0 when , The return value of the function is uncontrollable ;

notes ： Arguments can be constant 、 Variable or expression , But they are required to have certain values 、 Assign the value of the argument to the formal parameter variable when calling , If the parameter is an array name , Then the address of the first element of the array is passed ;

Nesting of functions

You cannot define another function within a function , But you can call another function ;
Functions cannot be nested , Calls can be nested

Recursion of a function

In the process of calling a function, it occurs to call the function itself directly or indirectly , Become a recursive call to a function ;
A recursive function includes two necessary conditions ：1. Exit of function ;2. Recurrence of functions ;

Global variables and local variables （ Internal variables ）

Global variables are all valid in this source program from the definition ;
Local variables are only valid in the defined function body ;
In the same function, if there are global variables and local variables with the same name , Global variables are masked , Local variable priority > Global variables

Ingenious notes ： The smaller the scope ; The greater the power ;

example ： There are five classes in grade three , There are two people named Zhang San in junior high school , But in a class , There is only one Zhang San , So I went to a class , Zhang San is only effective for Zhang San in this class , So in local variables , Global variables are masked ;

All variables defined in a function are local variables （ Unless otherwise stated ）, No default ;
All variables defined outside the function are global variables , Default assignment 0;

example ： The integer global variable is assigned 0;

The floating-point global variable is assigned 0.0;

Assign a value of ‘\0’;

All array global variables are assigned 0;

How variables are stored

Automatic variable ：auto： Variables defined when not declared are automatic variables ;

At the end of the calling function , These variables are automatically released ; Keywords can be omitted when defining ;

Static variables ：static： Variables will not be released after use ; Continue saving values
Register variables ：register： Variables stored in registers , It can be used to improve the operation speed ;
External variables ：extern： The default type of the function

The examination site of this chapter ：

The declaration of function should pay attention to the type of function , Name of function , The parameter type of the function ;

Remember some library functions that you often use ：

Library functions in the contents of the array

#include<math.h>// Remember to add header

abs（）// Find the absolute value （ plastic ）;

fabs（）// Find the absolute value （ floating-point ）;

sqrt（）// Find the square root （ The return type is double）;

pow（ , ）//2 The three times of can be pow（2,3） To calculate ;

sin（）// Find the value corresponding to the degree of trigonometric function ;

7、 ... and 、 The pointer

The concept of pointer

1. A pointer is the address of a variable in memory ;

2. If there is a variable dedicated to the address of another variable , Called pointer variables ;

3. The pointer stores the address of another variable , The values of all pointer variables are Address ;

4. The general form of pointer variables

Type name * Pointer variable name ;

5. stay 64（32） The memory occupied by pointers in bit computers is 8（4） Bytes ;

6. A pointer variable can only point to variables of the same type ;

7. If you want to assign a value to a pointer variable , Then it must point to a variable ;

8. When the parameter of the function is pointer type , His role is to put a The address of the variable Pass to function ;

9. There are two ways to return the value of a function ： adopt return Return value or use pointer to return value ;

Two 、 Notes on using pointer variables

1. What type of pointer variable points to what type of data ;

2. When defining a pointer variable , The pointer variable must be given an initial value, otherwise the wild pointer will appear and cause memory leakage ;

3. If a pointer variable is defined without an initial value assigned to NULL;

4. Pointer variables only receive addresses ;

5. Pointer variables do not receive constants ;

6. Pointers can perform relational operations 、 Subtraction , You can't add ;

*p++ It means to take out p The value of the pointer address and then the address plus 1;

++*p It means to take out p The value of the pointer address is then added 1;

（*p）++ It means to take out p The value of the pointer address and then add the value of the address 1;

*++p It means to first p My address plus 1, Then take out the value

*（p++） It means to take out p The value of the pointer address and then the address plus 1;

3、 ... and 、 Reference a string with a pointer

char *p// You can't be right *p assignment

char p[10]// You can re assign values to the array

Address of two-dimensional array ： It will convert the row address into the address of the first element of the row, point to the pointer of the function and return the pointer value ;

Be proficient in using pointers to point to one-dimensional arrays and two-dimensional arrays ;

8、 ... and 、 Structure 、 Shared body 、 enumeration

There are three ways to define a structure

ps： When initializing structure variables , To assign values to structure members one by one , Cannot skip previous member variables , And directly assign initial values to the following members , But you can only assign the first few , For the following unassigned variables , If it's numerical , It will be automatically assigned to 0, For character type , The initial value will be automatically assigned to NULL, namely ‘\0’;

Array of structs

Every element in the array is a variable of the same custom type .

Structure pointer ： Defining a structure pointer can be used to point to each item of the structure array ;

Four 、 Type of community (union)

1. In some algorithms C In language programming , Several different types of variables need to be stored in the same memory unit . That is, using coverage technology , Several variables cover each other . This kind of several different variables occupy a memory structure , stay C In language , It's called “ Shared body ” Type structure , Abbreviation: common body , It's also called a consortium .

2. The general form of the common body ：

Key knowledge points

4. The active member in the common variable is the last member to be assigned , After assigning a value to a member in the community variable , The value in the original variable storage unit is replaced .

The common body at any moment , Only one member is meaningful . also , Assign values to common variables , Only one variable can be assigned at any one time .
The size of the community is the size of the widest basic member , But divide by the widest basic member size .

Enumeration type （enum）

Is a named set of integer constants
Enumeration is not a number , But constant aggregate , That is, it may be one or more integer constants .
3. integer ： Namely int , It means that he can't be float Other types .
constant ： It shows that several numbers in this set cannot be changed .

nickname （typedef）

1.C Language allows a new alias for a data type , It's like giving people “ nickname ” equally .

2. Use typedef The names that were nicknamed before are still valid ;

for example ： Xiao Ming was nicknamed alarm , that “ Alarm ” It can also represent Xiao Ming ,“ Xiao Ming ” It can also represent Xiao Ming ;

Nine 、 file

Concept of documents

According to how the data is stored , Files can be divided into Binary and text file ;
text file ：ASCII file , Each byte stores one ASCII code Characters are easy to operate on characters . Such documents are in the form of EOF end .
Binary ： The data is stored according to its storage form in memory, which is convenient for storing intermediate results .

The concept of flow

It is divided into character stream or byte stream

file name

1. The composition of the document

File path （2） File backbone （3） file extension

Use file name

stay c In language ‘\’ For escape characters , So when writing a program, it needs to be written as ‘\\’

for example D:\str.doc For the file address to be used , It needs to be written as “D:\\str.doc”;

The file pointer

The file pointer actually points to a Structure Pointer to type , This structure contains ： The address of the buffer 、 The position of the currently accessed character in the buffer 、 To the file is “ read ” still “ Write ”、 Is it wrong 、 Whether you have encountered the end of file information flag and other information .
The general form of defining file type pointer variables is ：FILE * Pointer variable name ;
The file pointer comes from the header file #include<stdio.h>

Open and close files

The keyword to open the file is ：fopen( file name ,“ How to open the file ”);

The keyword to close the file is fclose（ The file pointer ）;
buffer ： In order to improve the transmission efficiency ;

Ten 、 Preprocessing

Macro definition #define

Macro definition format

#define < Macro name / identifier > < character string >

3、 ... and 、 Description of simple macro definition

1. Macro names are usually capitalized ;

2. No points are added at the end of the macro definition Number ;

3. Macro definitions can be nested

4. Macro replacement is performed before compilation , Don't allocate memory , Variable definition allocate memory , Function calls are made when the compiled program runs , And allocate memory

5. Preprocessing is before compiling , One of the tasks of compiling is grammar checking , Preprocessing does not do grammar check check .

Four 、 Macro definition with parameters

1. There can't be spaces between the parentheses of macro name and parameter ;

2. Macro replacement does not calculate , No expression solving ;

3. There is no type in the combination of macros , There is no type conversion ;

4. Macro expansion does not take up running time , It only takes compile time , Function calls occupy running ;