c ++ types of data each occupied by a byte length

c ++ in the various types of data type byte length occupied

First, a list of what data types in C ++ what are:

1, plastic: int, long

2, character: char, wchar_t

3, Boolean: bool

4, float: float, double

5, the pointer

 

First, plastic

　　int occupied by a memory cell size of the operating system. with the same long int

　　A previous 16-bit operating system is a 16-bit memory cell, it is 2 bytes; 32-bit system is a 32-bit memory cell, it is 4 bytes; 64-bit operating system is a 16-bit memory cell, so the accounting 8 bytes.

 

Second, character

　　char type generally occupies one byte, is used for the extended character set type wchar_t required to occupy two bytes.

 

Third, Boolean

　　occupies one byte bool

 

Fourth, the float

　　occupies 4 bytes float, double double float is 8 bytes

 

V. pointer

　　Pointer byte int length calculation principles are now almost digits to the operating system, and a pointer are equal, i.e., 32-bit system should be four bytes, 64-bit system should be 8 bytes.

 

code show as below

1 #include<iostream>                                                     
 2 
 3 using namespace std;
 4 
 5 int main()
 6 {
 7     int a;
 8     long b;
 9     char c;
10     wchar_t d;
11     bool e;
12     float f;
13     double g;
14     int*p= &a;
15 
16     cout << sizeof(a) << endl;
17     cout << sizeof(b) << endl;
18     cout << sizeof(c) << endl;
19     cout << sizeof(d) << endl;
20     cout << sizeof(e) << endl;
21     cout << sizeof(f) << endl;
22     cout << sizeof(g) << endl;
23     cout << sizeof(p) << endl;
24 }

The results are as follows

qqtsj@qqtsj-Nitro-AN515-51:~/cpp$ g++ -o size1 size1.cpp
qqtsj@qqtsj-Nitro-AN515-51:~/cpp$ ./size1
4
8
1
4
1
4
8
４

 

Its byte

 1 #include<iostream>
 2 
 3 using namespace std;
 4 
 5 struct A
 6 {
 7     int a;
 8     char b;
 9     short c;
10 };
11 
12 struct B
13 {
14     char a;
15     int b;
16     short c;
17 };
18 
19 #pragma pack(2)
20 struct C
21 {
22     char a;
23     int b;
24     short c;
25 };
26 
27 #pragma pack(1)
28 struct D
29 {
30     int a;
31     char b;
32     short c;
33 };
34 
35 int main(int argc, char ** argv)
36 {
37 
38     cout << sizeof(A) << "   "<< sizeof (B) << "   "<< sizeof (C) << "      "<< sizeof (D) <<endl;                                               
39     return 0;
40 }
~