C + + Primer NOTE 2 Basic built-in types

2-1 Note:

1, C + + only specifies the minimum size of each type of memory, while the number of bytes at least long long >=long>=int>=short;

2, the character type is divided into Char, signed char and unsigned char. The type char actually behaves as the above type, specifically determined by the compiler; VS2013, char = = signed char;

Suggestions:

1, clearly know that the value can not be negative, the use of unsigned type;

2, char only for storing characters, need a small integer, with signed char or unsinged char (clearly indicated);

3, the execution of floating point number with double (double with 2 words (64 bits) to represent precision);

2-2 Note:

1, non-bool->bool,0->false, non-0->true;

2, bool-> non-bool,false->0,true->1;

3. When assigning an unsigned type to a value that exceeds the range it represents, the result is that the initial value represents the remainder of the total number of numeric values for the unsigned type;

unsigned char =-1; (0~255);

Actual for -1%256 = 255; The remainder after modulo! 72235878

4. When we assign a symbol type to a value that exceeds the range it represents, the result is undefined!

Signed char c2 = 256; Assuming that Char occupies 8 bits, the value of C2 is undefined.

C + + Primer NOTE 2 Basic built-in types