- Five structures
1, definitions and concepts
struct structure type name
{
Member list
};
You can be redefined first described, and then they may be defined before the semicolon
Definition of the structure before the semicolon variable, while omitting the structure type name , it is no longer defined after such a structure variable is defined in this case only, the use of a limited number of commonly used global variables
typedef struct (structure type name optional)
{
Member list
} Type name ; semicolon before the variable is no longer defined
To define a variable simply type the name plus the variable name
Variable name assignment points plus Member Name
When the structure explained that the list of members can make another structure, can be used when the multi-level references
The same type of structure variables can be directly assigned to one another
2, array of structures
Array is an array of structures, a collection of a plurality of the same type of structure variable composition
struct structure type name array name [element number];
3, a structure pointer
Pointers to structures and methods for defined variables and the general assignment as
The overall structure and also references the same as ordinary variables
But when referring to members of different structures, need to add brackets. Higher priority than *, (* ps) .num
Bracketed trouble, can be used to point the operator (->) in place, ps-> num
When nested, the members inside the reference structure, the first layer a second layer with the operator pointing the dot operator
4, the structure memory allocation
Value at the specified alignment value #pragma pack (value).
value only: 1248, etc.
Byte alignment, the current value is an integer multiple of the members remains unchanged; value is less than the current member, but after adding a member happens to be an integral multiple of the same value; value is less than the current member, together with the latter member is also smaller than the integer value times the value of the integral multiples up.
Sizeof can be used to measure the space occupied
5, bit field (bit field)
struct packed_data
{
unsigned int a:2;
unsigned int b:6;
unsigned int c:3;
unsigned int :1; // 无意义的位段
unsigned int d:4;
unsigned int i;
} data;Colon behind the numbers that make up a few, can not take the address of a bit segment members
Do not exceed the range defined by the assignment bit segment, will range assignments interception operation
You can define meaningless bit segment, simple space, in order to ensure that members needed to occupy the back
The same structure, the member may include a variable bit segment and common member variables simultaneously
- Six, union
Similar structures and union, also a type of data structure configuration
The method defined in common body also defines a method and structure very similar to the struct into a union, as another method of use, but does not allow the bit segments
When performing certain algorithms, several different types of variables need to be stored in the same memory cell section, a space of several variables used in overlap
Body size of the common memory is that it accounts for the size of the maximum length of the member
Members of a union at the same time only an effective, commonly used in the process of sending the network protocol
- Seven, enumerated types
The value of the variable within a range of eleven enumerated value of the variable is limited to the enumerated value
enum enumeration type name
{
Enum values list (separated by commas members)
};
Typedef can also be used
With a local enumeration can be used instead of the macro definition, not vice versa
Enum members can be any content, the actual value is an integer incremented from zero by default, it may be changed by an integer value corresponding member to the member assignment
The definition of enumeration: enum enumeration type enum name names
