Cplusplus 简明教程

C++ Modifier Types

C++ 允许 char, int, * and *double 数据类型在其前面有修饰符。修饰符用于更改基类型的含义，使其更精确地适应各种情况的需求。

C++ allows the char, int, * and *double data types to have modifiers preceding them. A modifier is used to alter the meaning of the base type so that it more precisely fits the needs of various situations.

数据类型修饰符在此列出 -

The data type modifiers are listed here −

  1. signed

  2. unsigned

  3. long

  4. short

修饰符 signed, unsigned, long, 和 short 可以应用于整数基类型。此外， signed 和 unsigned 可以应用于 char，并且 long 可以应用于 double。

The modifiers signed, unsigned, long, and short can be applied to integer base types. In addition, signed and unsigned can be applied to char, and long can be applied to double.

修饰符 signed 和 unsigned 也可以用作 long 或 short 修饰符的前缀。例如， unsigned long int 。

The modifiers signed and unsigned can also be used as prefix to long or short modifiers. For example, unsigned long int.

C++ 允许使用一种简写表示法来声明 unsigned, short, 或 long 整数。您只需使用单词 unsigned, short, 或 long, ，而无需 int 。它会自动暗示 int 。例如，以下两个语句都声明无符号整数变量。

C++ allows a shorthand notation for declaring unsigned, short, or long integers. You can simply use the word unsigned, short, or long, without int. It automatically implies int. For example, the following two statements both declare unsigned integer variables.

unsigned x;
unsigned int y;

要理解有符号和无符号整数修饰符在 C++ 中的解析方式之间的差异，您应该运行以下简短程序 -

To understand the difference between the way signed and unsigned integer modifiers are interpreted by C++, you should run the following short program −

#include <iostream>
using namespace std;

/* This program shows the difference between
   * signed and unsigned integers.
*/
int main() {
   short int i;           // a signed short integer
   short unsigned int j;  // an unsigned short integer

   j = 50000;

   i = j;
   cout << i << " " << j;

   return 0;
}

当运行此程序时，以下为输出 -

When this program is run, following is the output −

-15536 50000

以上结果是因为表示短无符号整数 50,000 的位模式被短整数解析为 -15,536。

The above result is because the bit pattern that represents 50,000 as a short unsigned integer is interpreted as -15,536 by a short.

Type Qualifiers in C++

类型限定符提供有关其前面的变量的附加信息。

The type qualifiers provide additional information about the variables they precede.

Sr.No

Qualifier & Meaning

1

const Objects of type const cannot be changed by your program during execution.

2

volatile The modifier volatile tells the compiler that a variable’s value may be changed in ways not explicitly specified by the program.

3

restrict A pointer qualified by restrict is initially the only means by which the object it points to can be accessed. Only C99 adds a new type qualifier called restrict.