[C ++ Primer] Chapter 3 Study Notes (processing data)

Process Data
I. Classification

Basic Type + Composite Type
Basic types include integer and floating point

Composite types include: structure (struct)

Integer Classification
Integer: char short int long and unsigned
Float: float double long double
Boolean: boole is sometimes an integer.
Ii. Integer explanation

1. Expression

Short = short int
Long = long int
2. Function usage

Sizeof () // Length byte of the returned type
Sizeof variable // parentheses can be omitted

3. Use of infinite values

To obtain the extreme values of each type. You can add
# Include "limits. h"
INT_MAX, INT_MIN // represents the maximum and minimum integer values, respectively.

4. Differences between the number of unsigned characters and the number of signed characters
-128-127 0-255 short type; the highest bit of the unsigned number can be used as a value

5. Extreme Value addition and subtraction:
1> signed number: int max = INT_MAX;
Unsigned number: unsigned int un_max = INT_MAX;
Max ++
Un_max ++

Max =-2 ^ 31
Un_max = 2 ^ 32 + 1

2> signed number: short sam = 0;
Unsigned number: unsigned short un_sam = 0;
Sam --;
Un_sam --;

Sam =-1;
Un_sam = 255;

6, long; unsigned long: at least 64-bit
7. optimization considerations: If there are no large integers, use short (if possible)
Char can also
8, int a = 42; // decimal
Int B = 042; // hex
Int c = 0x42; // hexadecimal octal

 

Cout <"a =" <a <endl; // output in decimal format

Cout <"B =" <B <endl; // output in octal format
Cout Cout <"c =" <c <endl; // hexadecimal output
Cout <oct;

9. namespace
If cout is used like this
Std: cout <
Std: endl
Std: hex
Std: oct
The preceding keywords (cout, endl, hex, oct; such as int cout;) can be used as variable names.

Std: cout. put ('D'); // output function
10, const read-only

Const int;
A = 9;
// This is incorrect. After definition, the value cannot be changed.
Const is better than define
1> explicitly specify the type
2> you can use the scope to limit the range of variables defined by const to a file or function.
3. Floating Point Number
1. float 32-bit valid digits
Double 64-bit
Long double 80 96 128
Float can only represent the first six digits of a value

2. Forced type conversion does not change the value of the variable itself.

Int B = (int)
It does not change the value of a. It only changes the value of B.

From the column of ODA