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The first category: data type keywords

A basic data types (5)

Void declares that the function has no return value or arguments, declares no typed pointer, and explicitly discards the result of the operation.

Char character type data, which is a kind of integer data.

Int integer data, usually the machine word length specified by the compiler.

Float single-precision floating-point data is a kind of floating-point data. 6 digits are saved after the decimal point.

Double double-precision floating-point data is a kind of floating-point data, which is more accurate than float. It saves 15 seconds and 16 digits after the decimal point.

Type B modifier keywords (4)

Short modifies int, short integer data, and can omit the modified int.

Long modifies int, long × × data, but omits the modified int.

Signed decorates integer data with signed data types.

Unsigned decorates integer data, unsigned data types.

C complex type keywords (5)

Struct structure declaration.

Union common body declaration.

Enum enumeration declaration.

Typedef declares a type alias.

Sizeof gets the size of a specific type or type of variable.

D storage level keywords (6)

Auto is specified as an automatic variable, which is automatically assigned and released by the compiler. It is usually allocated on the stack.

Static is designated as a static variable, assigned in the static variable area, and when decorating a function, the scope of the function is specified within the file.

Register is specified as a register variable. It is recommended that the compiler store variables in registers, modify function parameters, and pass parameters through registers rather than stacks.

Extern specifies that the corresponding variable is an external variable, that is, defined in another object file, which can be considered to be declared by another file.

Const and volatile are collectively called "cv features" and specify that variables cannot be changed by the current thread / process (but may be changed by the system or other threads / processes).

Volatile and const are collectively called "cv features", and the value of a specified variable may be changed by the system or other process / thread, forcing the compiler to get the value of the variable from memory each time.

The second category: process control keywords

A jump structure (4)

Return is used in the function body to return a specific value (or a void value, that is, no value is returned).

Continue ends the current cycle and starts the next cycle.

Break jumps out of the current loop or switch structure.

Goto unconditional jump statement.

B branch structure (5)

If conditional statement

The else conditional statement negates the branch (used with if).

Switch switch statement (multiple branch statement).

The branch tag in the case switch statement.

The "other" divide and conquer in the default switch statement is optional.

C cycle structure (3)

For for loop structure, for (1 / 2 / 3) 4; the order of execution is 1-> 2-> 4-> 3-> 2. Loop, where 2 is the condition of the cycle.

Do do loop structure, do 1 while (2); the execution order is 1-> 2-> 1. Cycle, 2 is the condition of cycle.

The execution order of while while loop structure, while (1) 2; is 1-> 2-> 1. Loop, 1 is the loop condition, the above loop statement, when the loop condition expression is true, continue the loop, if false, jump out of the loop.

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