C language knowledge summary

C language outline

The first chapter is an overview.

1 and basic knowledge of c language

1. 1, C language execution steps

Edit-program code input, generate source program *. c

Compile-syntax analysis for error detection, and translation of the generated object program *.obj.

Grammatical or logical errors, change from the first one, variable definition, statement format, expression format, etc. )

Link and assemble with other target programs or libraries to generate an executable program *.exe.

carry out

Basic knowledge and main functions of 1.2

Location of the main () function

C programs always start with the main () function.

A C program can contain a main function, namely the main () function; You can also include a main () function and several other functions.

Structure and C Program of 1.3

Functions and main functions

A program consists of one or more functions.

There must be one and only one main function, main ()

Program execution starts from main and ends at main, and other functions are executed by nested calls.

Program statement

C program consists of statements.

Use ";" As a statement terminator

To annotate ...

/* */is a comment and cannot be nested.

Do not generate compiled code.

1.4, C programming rules

Used to use lowercase letters, case-sensitive.

There is no line number, and there is no concept of program line: usually one statement takes up one line.

You can use blank lines and spaces.

Commonly used zigzag writing format; Statements in the same hierarchy are aligned up and down.

Chapter 2, Basic Data Types and Operations

2. 1, data type of C program

Pay attention to the different meanings of types and variables (types are fixed names and variables are named by themselves)

Storage space occupied by variables

data type

Basic types: integer type, character type and floating-point type (single precision type and double precision type)

Structure type: array type, structure type.

Pointer type

Empty type

Pay attention to the way of assigning initial values to basic types.

Representation of basic data types

Shaping data

Decimal system: start with a non-zero number, such as: 123, -9, 0.

Octal; Start with the number 0, such as 0 123067.

Hexadecimal: starts with 0x, such as 0x 123, 0xff.

Real data

Decimal: Decimal point must be entered, such as: 123.0, -9.0.

Exponential form; Such as: 1.23E3, 0.9e-2, 5e2.

character data

Ordinary characters: such as' a',' 2',' h',' #'

Escape characters: such as' \ n',' \ 167',' \ XLF', \ \

(To align several columns: specify the width. E.g.% 100 \' \ t' tab stop)

(String length. " ABC \ n \ t \ \ " strlen 6； Size 7)

Storage length of basic data type

integer

Int byte number 2 digits 16 digits expression range -32768-32767.

Short 216-32768-32767

Long 432-2147483648-2147483647

Real type

Floating 4 32 3.4e-38-3.4e38

Shuang 8 641.7e-308-1.7e308

Character; Role; letter

char 1 8- 128- 127

2.2, identifier naming rules

Naming rules of C language identifiers

Identifiers consist of numbers, letters and underscores.

The first character of the identifier must be a letter and an underscore.

In C language, identifiers cannot be reserved words (keywords).

For example, the automatic external size of floating-point static case of structural char goto switch continues in typedef const if union default long unsigned do register void double return else short while enumsigned.

Arithmetic operator+-*/%

Relational operator >; & lt= = & gt= & lt= ! =

Logical operator! & amp& amp||

positional operator

Assignment operator = and its extended assignment operator

Conditional operator? ：

Comma operator,

Pointer operator *&;

Byte number operator sizeof

Forced type conversion operator (type)

Component operator. -& gt；

Subscript operator []

Others such as function call operator ()

Operator priority

From high to low: monocular operator, arithmetic operator, relational operator and assignment operator.

Description: Monocular operators: self-increasing operator, self-decreasing operator, type substitution operator. Combination direction: from right to left

For example+++-i first-i.

The combination direction of arithmetic operation is from left to right.

2.3 Basic operations and expressions

Relational expressions and logical expressions

(a>b) and amp&(x>y) (a = = b) || (x = = y)! = a | |(a & gt； b)

A & b.a is 0. B not implemented.

A||b a is 1. B not implemented.

The logical operation result in C: 1 stands for "true" and 0 stands for "false";

Judging whether an expression is true or not: 0 means "false" and non-0 means "true"

Conditional expression comma expression

For example, k=5, k++

The comma value is 5; K is 6.

The expression 1? Expression 2: Expression 3

K = 5 & gt6 ? 1 : 0

2.4. Data type conversion of mixed operation

2/3+0.5 double precision floating-point type

Chapter 3, Sequence Structure Programming.

3. 1, C sentence classification

simple statement

Expression statement expression+semicolon

An empty statement with only semicolons.

Compound statements enclose several statements in curly braces.

Process control statement

Select statement if, switch

Loop statements while, do while, for

Transfer statement break, continue, return goto

3.2. Format input function scanf

Universal format: scanf ("format control string", address list);

When using the scanf function, you need to pay attention to:

The number of format characters must be the same as the number of input items, the data type must be one-to-one, and the unformatted string (descriptive) should be completely input.

When entering execution data, you can enter integer data without decimal point.

When numeric data is mixed with characters or strings, you need to pay attention to the input method.

3.3. Format output function printf

Printf ("format control string", output list);

Specifies the output format, which consists of format string and unformatted string, and the unformatted string is output as it is.

%[Flag] [minimum output width] [. Accuracy] [Length] type

Logo:-Left alignment; +right alignment;

%f，%d，%c，%s

3.4. Other input and output functions

Putchar getchar puts gets

Chapter four, select structure programming.

If selection structure

Single branch

If (expression)

sentence

Double branch

If (expression)

Statement 1

other

Statement 2

Multi-branch

If (expression 1)

Statement 1

Else if (expression 2)

Statement 2

. . .

Else if (expression m)

Statement m

other

Statement n

Switch (expression)

{

Case constant expression 1: statement1; Break;

Case constant expression 2: statement 2; Break;

. . .

Case constant expression m: statement m; Break;

Default value: statement n; Break;

}

Pay attention to break

Chapter five, the program design of circular structure.

Three elements of circulation

Initial conditions; Termination conditions; Do something repeatedly between the initial condition and the termination condition (loop body)

While (emoticon)

sentence

While (emoticon);

For (the initial value assigned to the loop variable; Cyclic conditions; Cyclic variable increment)

(for()； // ; Execution time delay. Used for information exchange and so on. For example, for (I = 0, I

Break statement: it cannot be used for any other statement except loop statement and switch statement; Jump out of the loop.

Continue statement: skip the remaining statements in the loop body and force the next loop; Jump out of this cycle.

Chapter 6, Functions and Compilation Pretreatment

6. Definition and Call of1.Function

Type Identifier Function Name (Parameter Table)

Statement part

sentence

}

Example:

Int max (int x，int y)

{ int z； & ltbr & gtZ = x & gty？ x:y； & ltbr & gt returns (z); }

6.2, local variables and global variables

Pay attention to the definition and use of static variables in functions.

6.3, variable storage type

Storage type of local variables

Automatic variable (automatic) dynamic storage

Static storage of local static variables

Static storage of register variables.

Storage type of global variables

Automatic variable (automatic) dynamic storage

Static storage of external variables

Global static static storage

External external reference

Static cannot be referenced externally.

Chapter 7, Array

7. 1, the definition and use of one-dimensional array

Special attention should be paid to the initial value and termination conditions of the circulating body.

Example:

Master ()

{

Int I，a[ 10]；

for(I = 0； I < = 9; i++)

a = I；

for(I = 9； I & gt=0; I-)

Printf("%d "，a)；

}

Pay attention to the subscript problem

7.2, the definition and use of two-dimensional array

Initialization of two-dimensional array

For example:

Int a[3][4]={{ 1，2，3，4}，{5，6，7，8}，{9， 10， 1 1， 12 } }；

Int a[3][4]={ 1，2，3，4，5，6，7，8，9， 10， 1 1， 12 }；

Int a[ ][4]={ 1，2，3，4，5，6，7，8，9， 10， 1 1， 12 }；

Int a[ ][4]={{ 1，2，3，4}，{5}，{9， 10， 1 1， 12 } }；

For example: int a[3][3]={{ 1}, {2}, {3}};

Is to assign values to the elements in the first column of each row, and the unassigned elements take 0.

7.3. Character arrays and strings

Process a string with a character array and use the closing tag' \ 0'.

Such as: char c [] = {"I am very happy"};

Initializes a character array with string constants.

Char c[ ]={'I '，' '，' a '，' m '，' '，h '，' a '，' p '，' p '，' y '，' \ 0 ' }；

Chapter 8, Pointer

8. 1, the concept of address and pointer

int I；

Int * i _ point

8.2. Pointer variables and variable addresses

Operator: *&;

8.3, pointer and one-dimensional array

If there is a definition.

int a[ 10]；

int * p = a；

Analyze the meaning of the following expressions:

One,&one,

*(a+i)，a+i，

*(p+i)，p+i

A=*(a+i)=*(P+i)

& ampa=a+i=p+i

8.4. Pointers and strings

Master ()

{

Char string[ ]= "I love China!" ;

Printf("%s\n "，string)；

}

Master ()

{char *string= "I love China!" ;

Printf("%s\n "，string)；

}

8.5, pointer variables as function parameters

Definition of formal parameters; The form of true argument; How parameters are passed.

Chapter 9, Structure

9. 1, Definition of Structure Types and Variables

Structure name

{Member list};

Structural students

{ char stno[8]； & ltbr & gtchar name[20]； & ltbr & gt charming sex; & ltbr & gtInt age& ltbr & gt floating score; & ltbr & gtchar addr[30]； & ltbr & gt};

student

{ char stno[8]； & ltbr & gtchar name[20]； & ltbr & gt charming sex; & ltbr & gtInt age& ltbr & gt floating score; & ltbr & gtchar addr[30]； & ltbr & gt};

Stu 1, stu2, structural students

9.2. References to structural variables

The general form is:

Structure variable name. Member name

9.3. Structure array

Structure array structure array elements. Member name

Pointer variable to structure

(*p)。 Member name

p->； Member name

other

Strcpy (character array 1, string 2)

Strcat (character array 1, character array 2)