[C language] 32 keyword memory skills

The first category ： Data type key

A Basic data type （5 individual ）

1. void： Declare that the function has no return value or parameter , Declare no type pointer , Explicitly discard the result of the operation .
2. char： Character data type
3. int： Integer data type
4. float： Single precision floating point data （ A type of floating-point data , After the decimal point 6 position ）
5. double： Double precision floating point data （ A type of floating-point data , Than float High precision of type , After the decimal point 15/16 position ）

B Type modifier keyword （4 individual ）

1. short： modification int, Short integer data , Modified can be omitted int.
2. long： modification int, Long data , Modified can be omitted int.
3. signed： Modifying integer data , Signed data types .
4. unsigned： Modifying integer data , The unsigned data type .

C Complex type keywords （5 individual ）

1. struct： Structure declaration
2. union： Community statement
3. enum： Enum Declarations
4. typedef： Declare type aliases
5. sizeof： Get the size of bytes occupied by a specific type or a specific type variable

D Storage level keywords （6 individual ）

1. auto： Specified as an automatic variable , Automatically allocated and released by the compiler （ Usually allocated on the stack ）.
2. static： Specified as a static variable , Assigned in the static variable area . When modifying a function , Specifies that the function scope is inside the file .
3. register： Specified as a register variable , It is recommended that the compiler store variables in registers ; You can also modify function parameters , It is recommended that the compiler pass parameters through registers rather than stacks .
4. extern： Specifies that the corresponding variable is an external variable , That is, the definition in another object file , It can be said that the agreement is declared by another document .
5. const： And volatile combined term “ cv characteristic ” , The specified variable cannot be used by the current thread / The process changes （ But it could be by the system or other threads / The process changes ）.
6. volatile： And const combined term “ cv characteristic ” , The value of the specified variable may be changed by the system or other threads / The process changes , Force the compiler to get the value of the variable from memory at a time .

The second type of process control keywords

A Jump structure （4 individual ）

1. return： In the body of a function , Returns a specific value （ or void value , That is, no value is returned ）.
2. continue： End the current cycle , Start next cycle .
3. break： Jump out of the current loop or Switch structure
4. goto： Jump statements without conditions

B Branching structure （5 individual ）

1. if： Conditional statements
2. else： Conditional statement negates Branch （ And if Continuous use ）
3. switch： Switch statement （ Multiple branch statements ）
4. case： Branch markers in switch statements
5. default： In the switch statement “ other ” Branch （ Optional ）

C Loop structure （3 individual ）

1. for：for Loop structure for(①;②;③) ④ ; The execution order of is ①→②→④→③→②→④… loop , among ② Is the cyclic condition .
2. do：do Loop structure do ① while(②) ; The execution order of is ①→②→①→②→①… loop , among ② Is the cyclic condition .
3. while：while Loop structure while(①) ② ; The execution order of is ①→②→①→②→①… loop , among ① Is the cyclic condition .

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