C Language Summary

C language Composition

Variable statement function

Variable type: integer variable character variable floating-point variable (single-precision and double-precision floating-point type) void type

Char: one byte

Short:2 bytes

INT: Follow system 32-bit system 4 bytes

Float:4 bytes

Long:4 bytes

Double:8 bytes

A long double:10 bytes

type name	Number of bytes	Other Salutation	range of Values
Int	*	Signed, Signed int	Depends on operating system
unsigned int	*	Unsigned	Depends on operating system
__int8	1	Char Signed Char	-128 to 127
__int16	2	Short Short int, Signed Short int	-32,768 to 32,767
__int32	4	Signed, Signed int	-2,147,483,648 to 2,147,483,647
__int64	8	None	-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
Char	1	Signed Char	-128 to 127
unsigned char	1	None	0 to 255
Short	2	Short int, Signed Short int	-32,768 to 32,767
unsigned short	2	unsigned short int	0 to 65,535
Long	4	Long int, Signed Long int	-2,147,483,648 to 2,147,483,647
unsigned long	4	unsigned long int	0 to 4,294,967,295
Enum	*	None	Same as int
Float	4	None	3.4E +/-(7 digits)
Double	8	None	1.7E +/-308 (digits)
Long double	10	None	1.2E +/-4932 (digits)

sizeof can find bytes

Limit.h inside Int_max can find maximum value int_min can be minimized

Declaring the meaning of a variable can be reused, and variable names can be read as much as possible when declaring variables

Statement: Sequential statement Loop Statement selection Statement (branch statement)

Sequential statements

Looping statements: for And while Do......while

SELECT statement: Switch

Function

Pointer: A memory space where the address is stored, and the pointer type determines how the content pointed to by the pointer is read. The address of the pointer holds the accuracy of the data (a memory leak occurs when an int pointer is held in a char type pointer, and the char type pointer is placed in the int type to produce some garbage values)

A struct can return multiple values, and a pointer can return only one value in C, and multiple values may be returned in C + +

Use variables instead of pointers whenever possible

Call to function

The call to the function is backtracking through the stack, and the arguments are passed through the stack.

C-language parameter delivery pass is an alias copy

Local variables

Pass-through parameter return address stored in the stack

Local variables consume memory in use, and when the function life cycle ends, it frees the current stack (local variables are released at this time)

1. When the function is called, it encounters a return, and if the function returns the address of a local variable, the address is invalid because the stack copies a copy when the called function is in use. After it is finished, the address of this local variable will be invalid, and the copy will not return to the address of the local variable in the original calling function.

2. When passing parameters, the function copies a copy of the current parameters to the stack for parameter passing, so any changes you make to the parameters within the function are modified aliases, and the copy itself does not change anything, because the value he holds does not change.

If you want to change the action to itself, pass in the address of the local variable.

The program occupies a piece of memory, as long as we can access the current memory in the program

Heap Area

Special area, managed by programmer, malloc allocates space.

Scope of use: More than 1MB there is another way to not want the program to release the space variables you allocated

Stack area

Use range: Only one use can not exceed 1MB, otherwise it will cause stack overflow

Global zone (static variable)

Global variables

Global constants

Code Area

C Language Summary