Basic programming is also required core data type knowledge point, to be able to distinguish the different data types and data representation need to define data types. Different system or programming language, when you define data types may differ in the use of learning to distinguish, to avoid confusion, here I am a simple distinction between data and summary deepen the impression of it.
Java data types
Eight kinds of basic data types: byte, short, int, long, float, double, char, boolean.
| Types of | description | range |
|---|---|---|
| byte | 8, there is a symbol, a default value of 0 | -2^7 - 2^7 -1 |
| short | 16-bit, signed, a default value of 0 | -2^15-2^15 -1 |
| int | 32-bit, signed, a default value of 0 | -2^31-2^31 -1 |
| long | 64-bit, signed, Default 0L | -2^63-2^63 -1 |
| float | Single precision 32-bit, default values 0.0f | |
| double | 64-bit double precision, the default value 0.0d | |
| char | A single 16-bit Unicode characters | \u0000-\uffff |
| boolean | One bit, false / true | true/false |
Reference data types: arrays, classes, interfaces
C data types
C language has four types of data types
| Types of | Contained type |
|---|---|
| Basic data types ( Basic the Data Type ) | char,int, float, double |
| Derived Data Types ( Derived the Data Type ) | array, pointer, structure, union |
| Enumerated data type ( Enumeration the Data Type ) | enum |
| Void data type ( void the Data the Type ) | void |
C language basic data types: memory size may vary according to the 32-bit or 64-bit operating system; not marked in the unsigned case, most are signed by default.
| Types of | description | Value range |
|---|---|---|
| char | 1 byte / 8, character type | -128 to 127 |
| unsigned char | 1 byte / 8 bits, unsigned char | 0 to 255 |
| short | The 2-byte / 16-bit short integer | -32,768 to 32,767 |
| unsigned short | The 2-byte / 16-bit, unsigned short | 0 to 65,535 |
| int | 4-byte / 32-bit, integer | -2,147,483,648 to 2,147,483,647 |
| unsigned int | 4-byte / 32-bit, unsigned int | 0 to 4,294,967,295 |
| long | 4-byte / 32-bit long integer | -2,147,483,648 to 2,147,483,647 |
| unsigned long | 4-byte / 32-bit, unsigned long | 0 to 4,294,967,2957 |
| float | 4 bytes significant digits 6-7 | -3.4E-38 to 3.4E + 38 |
| double | 8 byte, 15 to 16 significant digits | -1.7E-308 to 1.7E + 308 |
| long double | 16 bytes, 18 to 19 significant digits | -1.2E-4932 to 1.2E + 4932 |
Note: C language itself is not bool type, generally with a substituted or custom int enumeration. However, inside the C99 standard, also defined bool type variable, as long as the introduction header <stdbool.h>, can be properly used in the C language type bool.
C ++ Data Types
Overall, the basic C ++ data types and C language almost.
| Types of | Keyword |
|---|---|
| Character | char |
| Integer | int |
| Float | float/double |
| Boolean | bool |
| Wide character | wchar_t |
| Untyped | void |
You may use one or more types of modified modifiers: signed, unsigned, short, long.
| Types of | description | range |
|---|---|---|
| char | 8/1 byte | -128 to 127 or 0 to 255 |
| unsigned char | 8/1 byte | 0 to 255 |
| int | 32-bit / byte 4 | -2147483648 to 2147483647 |
| unsigned int | 32-bit / byte 4 | 0-4294967295 |
| short int | 16/2 byte | -32768 to 32767 |
| unsigned short int | 16/2 byte | 0 to 65,535 |
| long int | 64/8 bytes | -/+9,223,372,036,854,775,808 |
| unsigned long int | 64/8 bytes | 0 to 18,446,744,073,709,551,615 |
| float | 4 bytes | +/- 3.4e +/- 38 (~ 7 digits) |
| double | 8 bytes | +/- 1.7e +/- 308 (~ 16 digits) |
| long double | 16 bytes | +/- 1.2e +/- 4932 (~19 个数字) |
| wchar_t | 2 或 4 字节 | 1 个宽字符 |
补充：在C/C++中可以使用sizeof()运算符返回数据类型所占的内存字节，32位系统和64位系统的结果可能是不同的。下面是一个简单的对比：
| 数据类型 | 32位编译器 | 64位编译器 |
|---|---|---|
| char | 1个字节 | 1个字节 |
| char*（即指针变量） | 4个字节 | 8个字节 |
| short int | 2个字节 | 2个字节 |
| int | 4个字节 | 4个字节 |
| unsigned int | 4个字节 | 4个字节 |
| float | 4个字节 | 4个字节 |
| double | 8个字节 | 8个字节 |
| long | 4个字节 | 8个字节 |
| long long | 8个字节 | 8个字节 |
| unsigned long | 4个字节 | 8个字节 |