C++ Primitive Data Types_C/C++_编程开发_程序员俱乐部

1. Numeric Data Types( 9 kinds )

? ? Name Synonymy Strorage Size

? ? short ? short int? 16-bit signed

? ? unsigned short? unsigned short int? 16-bit unsigned

? ? int --- 32-bit signed

? ? unsigned int? unsigned 32-bit unsigned

? ? long long int? 32-bit signed

? ? unsigned long? unsigned long int? 32-bit unsigned

? ? float --- 32-bit IEEE 754

? ? double --- 64-bit IEEE 754

? ? long double? --- 80-bit

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2. Numeric Type Convertions

• if one of the operands is long double, the other is converted into long double;
• Otherwise, if one of the operands is double, the other is converted into double;
• Otherwise, if one of the operands is float, the other is converted into float;
• Otherwise, if one of the operands is unsigned long, the other is converted into unsigned long;
• Otherwise, if one of the operands is long, the other is converted into long;
• Otherwise, if one of the operands is unsigned int, the other is converted into unsigned int;
• Otherwise, both operands are converted into int.

? ? ? Casting Operator : static_cast<type>(value)
3. ?Character Data Type ? ? ?Name StorageSize ? ? ?char? ? ? ? ? ? ? ? ? ? ? ? ?1 character?
4. Casting between char and Numeric Types

• char can be cast into any numberic type, and vice versa.
• When an integer is cast into a char, only its lower 8 bits of data are used.
• When a floating-point value is cast into a char, the floating-point vlaue is first cast into an int, which is then cast into a char.

5. bool Data Type ? ? Name StorageSize ? ? bool ? ? ? ? ? ? ? ? ? ? ? ?1 character? ? ? In C++, any nonzero value evaluates true and zero value evaluates false. ?

6. widening a type v.s. narrowing a type?

• widening a type : casting a variable of a type with a small range to a variable of a type with a larger range.
• narrowing a type : casting a variable of a type with a large range to a variable of a type with a smaller range.?
• Narrowing a type may lose precision.

7. switch ( switch-expression ) ? ? In C++, a char or bool value is treated as an integral. So, this type of value used in a switch statement as a switch expression or case value.

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