Cprogramming 简明教程

Special Characters in C

C 语言识别一个包含英语字母（大写和小写（A 到 Z 以及 "a" 到 "z"）、数字 0 到 9 和某些称为“特殊字符”且带有特定含义的其他符号的字符集。

The C language identifies a character set that comprises English alphabets – upper and lowercase (A to Z as well as "a" to "z"), digits 0 to 9, and certain other symbols called "special characters" with a certain meaning attached to them.

虽然特殊符号类别中的许多字符被定义为运算符，但某些字符组合也具有特殊的含义。例如， "\n" 称为 newline character. 此类组合称为 escape sequences 。

While many of the characters in the special symbol category are defined as operators, certain combinations of characters also have a special meaning attached to them. For example, "\n" is known as the newline character. Such combinations are called escape sequences.

在 C 语言中，引号也具有特殊的含义。双引号用于字符串，而字符用单引号括起来。阅读此章节以详细了解在 C 程序中使用的其他特殊字符。

In C language, quotation marks too have a special meaning. Double quotes are used for strings, while characters are enclosed inside single quotes. Read this chapter to learn more about the other special characters used in C programs.

Parentheses ()

括号特别用于对表达式中一个或多个运算数进行分组，并控制语句中的运算顺序。

Parentheses are especially used to group one or more operands in an expression and control the order of operations in a statement.

括号内嵌入了部分表达式，其优先级更高。

A part of the expression embedded inside parentheses has a higher order of precedence.

Example

int a = 2, b = 3, c = 4;
int d = (a + b) * c;

Braces { }

大括号特别用于定义代码块，例如 function 正文和 loops 。它们还用于初始化 arrays 和 struct variables 。

Braces are especially used to define blocks of code, such as function bodies and loops. They are also used to initialize arrays and struct variables.

Examples

大括号在函数定义中 -

Braces in function definition −

int add(int a, int b){
   int sum = a + b;
   return sum;
}

大括号在数组初始化中 -

Braces in array initialization −

int arr[5] = {1, 2, 3, 4, 5};

大括号在结构变量中 -

Braces in struct variable −

struct book {
   char title[10];
   double price;
   int pages;
};
struct book b1;
struct book b1 = {"Learn C", 675.50, 325};

Square Brackets [ ]

方括号用于声明数组和使用下标索引访问数组元素。

Square brackets are used to declare arrays and access elements of an array with the subscript index.

Example

例如，要定义一个整数数组并访问其第三个元素，可以使用方括号 -

For example, to define an array of integers and access its third element, you would use square brackets −

int arr[5] = {1, 2, 3, 4, 5};
int third = arr[2];

Asterisk (*)

除了将其用作乘法运算符之外，星号 (*) 符号还用于声明 pointer variable 并 dereference 它以获得目标变量的值。

Apart from its use as a multiplication operator, the asterisk symbol (*) is also used to declare a pointer variable and dereference it to obtain the value of the target variable.

Example

例如，要定义一个指向整数的指针并访问它指向的值，可以使用星号 -

For example, to define a pointer to an integer and access the value it points to, you would use an asterisk −

int num = 10;
int *ptr = #
printf("*d", *ptr);

Ampersand (&)

"&" 符号用作 address-of operator 。它返回变量的地址。

The ampersand (&) symbol is used as the address-of operator. It returns the address of a variable.

Example

例如，要获取一个整型变量的地址，可以使用一个 & -

For example, to get the address of an integer variable, you would use an ampersand −

int num = 10;
int *ptr = #

Comma (,)

逗号用作语句或函数调用之间的分隔符。

The comma is used as a separator between a statement or a function call.

Example

int a = 1, b = 2, c = 3;

Semicolon (;)

作为 C 中的一个主要语法规则，分号指明 C program 中语句的结束。

As a primary syntax rule in C, the semicolon indicates the end of a statement in a C program.

Example

printf("Hello, world!");

Dot (.)

dot symbol (.) 用于访问结构或 union 的成员。

The dot symbol (.) is used to access the members of a structure or a union.

Example

struct book b1 = {"Learn C", 675.50, 325};

printf("Title: %s\n", b1.title);
printf("Price: %lf\n", b1.price);
printf("No of Pages: %d\n", b1.pages);

Arrow (→)

箭头符号 (→) 用于通过指针来访问结构或联合的成员。

The arrow symbol (→) is used to access the members of a structure or a union through a pointer.

Example

struct book b1 = {"Learn C", 675.50, 325};
struct book *strptr;
strptr = &b1;

printf("Title: %s\n", strptr->title);
printf("Price: %lf\n", strptr->price);
printf("No of Pages: %d\n", strptr->pages);