================ Chapter one =================

C The advantages of : Design features , Efficiency , Portability , Powerful functionality and flexibility , For programmers

shortcoming : Freedom of expression increases the risk of procedure , The price of freedom is always vigilance

use C The seven steps of : Define program objectives , Design procedure , Write code , compile , Run the program , Testing and commissioning procedures , Maintenance and modification procedures , notes

C Programming mechanism of language : The compiler converts the source code into a target executable file ( Is an incomplete program that contains machine code ), The linker will precompile the library code , The standard startup code and object code of the system are combined together , Convert to executable , This file contains machine code that can be run .

C Language standards :ANSI/ISO C standard → C90 standard → C99 standard

================ Chapter two =================

C Interpretation of procedures


#include <stdio.h>

This is a preprocessor instruction   

stdio.h Represents the input and output header file standard input/output header

Another common pitfall of compilers is that the errors found are one line behind the real ones

Debugging code should be faithful to the actual code

================ Chapter three =================

C Data type graph of language


Integer type

include (unsigned)long long int ,(unsigned) long int, (unsigned) int,(unsigned)
short int,(unsigned) char

System processing int Type of data is the fastest , According to the size of the storage space, the processing speed of others slows down in turn

The content expressed in single quotation marks character , The content expressed in double quotation marks character string

In the same system :long long int (8 byte ) > long int (4 byte ) > int (2 ~ 4 byte ) > short (2 byte ) >
char (1 byte )

It can be used LL,L,LU,LLU As a suffix to a number, it identifies different data types `

The overflow of integer data type is a problem worth studying , It includes the following aspects :

1, Overflow of conversions between different data types

2, Overflow occurred in signed and unsigned data type conversion

Floating Point Types

float (4 byte , Significant number at least 6 position ) > double (8 byte , Significant number at least 10 position ) > long double ( at least 8 byte , Significant number at least 10 position )

The overflow and underflow of floating-point data type is worth studying , It includes the following aspects :

1, Data overflow

2, Data underflow

Complex and imaginary types complex.h

_Complex _Imaginary

Portable types :inttypes.h


_Bool type

1 representative true, 2 representative false

Escape sequence

================ Chapter four =================

Strings are stored in character arrays , Each unit is a character , In the end \0 ( Empty character ) end .
scanf() After reading input , In the first white space encountered (blank), Tab (tab) Or line breaks (newline) Stop reading at .
sizeof and strlen() The difference between

sizeof Gives the size of the data in bytes ,strlen() Function gives the length of a string in characters , Specific examples are as follows :

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