C++ Primitive Data Types

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

 

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.