[C language _ study _ exam _ review lesson 3] overview of ASCII code and C language

 【C Language _ Study _ The test _ Review lesson 3 】ASCII Code and C Language Overview

ASCII Code and C Language Overview

Ask every day :10101111 Use octal 、 Decimal system 、 Hexadecimal indicates how much ?

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 【C Language _ Study _ The test _ Review lesson 2 】ASCII Code and C Language Overview

What is? ASCII code ？

C Language Overview

 C The structure of language : 

C Language features ：

C Language identifier

Colored eggs

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What is? ASCII code ？

ASCII ((American Standard Code for Information Interchange): American standard code for information exchange ） Is based on Latin alphabet A set of computers Programming System , Mainly used to show modern English And others Western Europe Language . It is the most versatile Information standard , It's the same as The international standard ISO/IEC 646.ASCII The first time it was published as a standard type was in 1967 year , The last update was in 1986 year , So far, we have defined 128 Characters

00000000B-11111111B 0-127 altogether 128 Encoding

In general, we just need to remember

A-Z 65-90

a-z 97-122

0-9 48-57

Space (space)32

common ASCII The size rule of the code :

1 Numbers are smaller than letters

2 Numbers 0 More than numbers 9 smaller

3 Letter A Than letters Z smaller , And press A To Z The order is increasing .

4 The upper case of the same letter is smaller than the lower case 32.

C Language Overview

C Language is a kind of computer programming language , It has the characteristics of high-level language and assembly language . It can be used as the system setting language , Write work system applications , It can also be used as an application design language , Write application systems that do not rely on computer hardware .

C The extension of the program written in language is .C, After compilation, the extension of the generated file is .obj( Engineering documents ), The extension of the linked file is .exe( Executable file ).

C Language belongs to compiled language .

 C The structure of language : 

1. A program consists of one or more source files
2. The function is c An important part of the program
3. A function consists of two parts Function radical The body of the function
4. The program always starts from main The function starts executing
5. The operation that the computer is required to complete in the program is performed by c Language accomplished .
6. Every data declaration and statement must have a semicolon at the end .
7. C The language itself does not provide input and output statements
8. The program should include comments

C Language features ：

The function is c programmatic Basic unit

The program always starts from main Function start execution ,main End of the function ,main The position of the function is arbitrary .

Statement plus ; End of the said

The sentence is c Linguistic The smallest constituent unit .

One line can write one or more statements , A statement can also be written as one or more lines .

C Language identifier

The composition of the identifier ：

Identifier by number 、 The character slide line is composed of . It can only start with letters and slide lines

Classification of identifiers ：

1. keyword (c99)

auto	break	case	char	const	continue	default	do
double	else	enum	extern	float	for	goto	if
int	long	register	return	short	signed	sizeof	static
struct	switch	typedef	union	unsigned	void	volatile	while

2. User defined identifier ( That is, name )

C Languages are case sensitive

1. Predefined identifiers

for example ：scanf( Input function )、printf( Output function )、include( File contains )、define( Macro definition ) etc. .

Be careful ：C Language keywords cannot be used for user identifiers

           C Language keywords are lowercase letters

             Identifiers are case sensitive

Colored eggs

Little knowledge :C Language used to be called B Language

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