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There are 32 keywords in C language. According to the function of keywords, they can be divided into four categories: data type keywords, control statement keywords, storage type keywords and other keywords. There are 12 data type keywords, including char, double, float, int, etc.; there are 12 control statement keywords, including for, break, if, else, do, etc.; there are 4 storage type keywords, including auto, static , extern, etc.; there are 4 other keywords, including const, sizeof, etc.
The operating environment of this tutorial: windows7 system, c99 version, Dell G3 computer.
C language is concise, compact, easy to use and flexible. C language has a total of 32 keywords and 9 control statements. The program can be written in a free form and is case-sensitive. Combine the basic structures and statements of high-level languages with the practicality of low-level languages. C language can operate on bits, bytes and addresses just like assembly language, and these three are the most basic working units of computers.
C language has a total of 32 keywords, as shown in the following table:
Keyword | Description |
---|---|
auto | Declare automatic variables |
short | Declare short integer variables or functions |
int | Declare an integer variable or function |
long | Declare a long integer variable or function |
float | Declare a floating-point variable or function |
double | Declare a double-precision variable or function |
char | Declare character variables or functions |
struct | Declare structure variables or functions |
union | Declaration of shared data types |
enum | Declaration of enumeration types |
typedef | Used to alias the data type |
const | Declare read-only variables |
unsigned | Declare unsigned type variables or functions |
signed | Declare signed type variables or functions |
extern | Declared variables are declared in other files |
register | Declared register variables |
static | Declare static variables |
volatile | Indicates that variables can be changed implicitly during program execution |
void | Declare a function with no return value or parameters, declare an untyped pointer |
if | Conditional statement |
else | Conditional statement negation branch (used with if) |
switch | Use On switch statement |
case | Switch statement branch |
for | A kind of loop statement |
do | The loop body of the loop statement |
while | The loop condition of the loop statement |
goto | Unconditional jump statement |
continue | End the current loop and start the next cycle |
break | Jump out of the current loop |
default | The "other" branch in the switch statement |
sizeof | Calculate data type length |
return | Subroutine return statement (can be with or without parameters Parameters) Loop condition |
C language keyword types
According to the function of keywords, they can be divided into four categories: data type keywords, control statement keywords, storage type keywords and other keywords. .
1. Data type keywords (12):
(1) char: declare a character variable or function
(2) double: declare a double precision variable or function Function
(3) enum: declares an enumeration type
(4) float: declares a floating-point variable or function
(5) int: declares an integer variable or function
(6) long: Declare a long integer variable or function
(7) short: declare a short integer variable or function
(8) signed: declare a signed type variable or function
(9) struct: declare a structure variable or Function
(10) union: declare a union (union) data type
(11) unsigned: declare an unsigned type variable or function
(12) void: declare a function with no return value or parameters, declare Untyped pointer (basically these three functions)
2. Control statement keywords (12):
A loop statement
(1) for: a kind of loop statement (can be understood but not expressed in words)
(2) do: the loop body of the loop statement
(3) while: the loop condition of the loop statement
(4) break: jump out of the current loop
(5) continue: End the current loop and start the next cycle
B conditional statement
(1)if: conditional statement
(2)else: Conditional statement negation branch (used with if)
(3)goto: unconditional jump statement
C switch statement
(1)switch: used for switch statement
(2)case: switch statement branch
(3)default: "other" branch in the switch statement
D return statement
return: subroutine return statement ( Parameters can be taken or not)
3. Storage type keywords (4)
(1)auto: Generally not used to declare automatic variables
(2)extern: Declaring variables is declared in other files (can also be regarded as reference variables)
(3)register: Declaring register variables
(4)static: Declaring static variables
4. Other keywords (4):
(1)const: declare read-only variables
(2)sizeof: calculate the length of the data type
(3)typedef: used to give Aliasing data types (of course there are other functions
(4)volatile: Indicates that variables can be changed implicitly during program execution
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