The number of bytes, range size, and overflow handling of C++ basic data types

C++ has several basic data types: char, int, float, double. The number of bytes and range of these data types vary depending on the operating system and compiler.

Figure (1) The number of bytes of C++ basic data types

On Windows, the same basic data type has the same number of bytes in win32 and win64 ; for example, int has 4 bytes in both win32 and win64.
On Linux, most basic data types have the same number of bytes in 32-bit and 64-bit; only the long type is different (except for long long, of course, long long is available on both 32-bit and 64-bit Linux) is 8 bytes). For example, float is 4 bytes on 32-bit and 64-bit Linux; double is 8 bytes on 32-bit and 64-bit Linux.

Currently, in Windows, some compound data types have different byte counts in different bits. For example, for compound data types such as string and size_t, string occupies 28 bytes on win32 and 40 bytes on win64. size_t occupies 4 bytes on win32 and 8 bytes on win64.

1. Windows system

1.1 32-bit compiler

32位 Windows上的数据类型与范围
type:           ************size**************
bool:           所占字节数：1   最大值：1               最小值：0
char:           所占字节数：1   最大值：127             最小值：-128
signed char:    所占字节数：1   最大值：127             最小值：-128
unsigned char:  所占字节数：1   最大值：255             最小值：0
wchar_t:        所占字节数：2   最大值：65535           最小值：0
short:          所占字节数：2   最大值：32767           最小值：-32768
int:            所占字节数：4   最大值：2147483647      最小值：-2147483648
unsigned:       所占字节数：4   最大值：4294967295      最小值：0
long:           所占字节数：4   最大值：2147483647      最小值：-2147483648
unsigned long:  所占字节数：4   最大值：4294967295      最小值：0
double:         所占字节数：8   最大值：1.79769e+308    最小值：2.22507e-308
long double:    所占字节数：8   最大值：1.79769e+308    最小值：2.22507e-308
float:          所占字节数：4   最大值：3.40282e+38     最小值：1.17549e-38
size_t:         所占字节数：4   最大值：4294967295      最小值：0
string:         所占字节数：28
type:           ************size**************

1.2 64-bit compiler

64位 Windows上的数据类型与范围

type:           ************size**************
bool:           所占字节数：1   最大值：1                       最小值：0
char:           所占字节数：1   最大值：127                     最小值：-128
signed char:    所占字节数：1   最大值：127                     最小值：-128
unsigned char:  所占字节数：1   最大值：255                     最小值：0
wchar_t:        所占字节数：2   最大值：65535                   最小值：0
short:          所占字节数：2   最大值：32767                   最小值：-32768
int:            所占字节数：4   最大值：2147483647              最小值：-2147483648
unsigned:       所占字节数：4   最大值：4294967295              最小值：0
long:           所占字节数：4   最大值：2147483647              最小值：-2147483648
unsigned long:  所占字节数：4   最大值：4294967295              最小值：0
double:         所占字节数：8   最大值：1.79769e+308            最小值：2.22507e-308
long double:    所占字节数：8   最大值：1.79769e+308            最小值：2.22507e-308
float:          所占字节数：4   最大值：3.40282e+38             最小值：1.17549e-38
size_t:         所占字节数：8   最大值：18446744073709551615    最小值：0
string:         所占字节数：40
type:           ************size**************

In Windows, the case program for obtaining the number of bytes and range size of the data type is as follows:
//getSize.cpp

#include<iostream>  
#include <limits>

using namespace std;

int main()
{
    
    
    cout << "type: \t\t" << "************size**************" << endl;
    cout << "bool: \t\t" << "所占字节数：" << sizeof(bool);
    cout << "\t最大值：" << (numeric_limits<bool>::max)();
    cout << "\t\t最小值：" << (numeric_limits<bool>::min)() << endl;
    cout << "char: \t\t" << "所占字节数：" << sizeof(char);
    cout << "\t最大值：" << (int)(numeric_limits<char>::max)();
    cout << "\t\t最小值：" << (int)(numeric_limits<char>::min)() << endl;
    cout << "signed char: \t" << "所占字节数：" << sizeof(signed char);
    cout << "\t最大值：" << (int)(numeric_limits<signed char>::max)();
    cout << "\t\t最小值：" << (int)(numeric_limits<signed char>::min)() << endl;
    cout << "unsigned char: \t" << "所占字节数：" << sizeof(unsigned char);
    cout << "\t最大值：" << (int)(numeric_limits<unsigned char>::max)();
    cout << "\t\t最小值：" << (int)(numeric_limits<unsigned char>::min)() << endl;
    cout << "wchar_t: \t" << "所占字节数：" << sizeof(wchar_t);
    cout << "\t最大值：" << (numeric_limits<wchar_t>::max)();
    cout << "\t\t最小值：" << (numeric_limits<wchar_t>::min)() << endl;
    cout << "short: \t\t" << "所占字节数：" << sizeof(short);
    cout << "\t最大值：" << (numeric_limits<short>::max)();
    cout << "\t\t最小值：" << (numeric_limits<short>::min)() << endl;
    cout << "int: \t\t" << "所占字节数：" << sizeof(int);
    cout << "\t最大值：" << (numeric_limits<int>::max)();
    cout << "\t最小值：" << (numeric_limits<int>::min)() << endl;
    cout << "unsigned: \t" << "所占字节数：" << sizeof(unsigned);
    cout << "\t最大值：" << (numeric_limits<unsigned>::max)();
    cout << "\t最小值：" << (numeric_limits<unsigned>::min)() << endl;
    cout << "long: \t\t" << "所占字节数：" << sizeof(long);
    cout << "\t最大值：" << (numeric_limits<long>::max)();
    cout << "\t最小值：" << (numeric_limits<long>::min)() << endl;
    cout << "unsigned long: \t" << "所占字节数：" << sizeof(unsigned long);
    cout << "\t最大值：" << (numeric_limits<unsigned long>::max)();
    cout << "\t最小值：" << (numeric_limits<unsigned long>::min)() << endl;
    cout << "double: \t" << "所占字节数：" << sizeof(double);
    cout << "\t最大值：" << (numeric_limits<double>::max)();
    cout << "\t最小值：" << (numeric_limits<double>::min)() << endl;
    cout << "long double: \t" << "所占字节数：" << sizeof(long double);
    cout << "\t最大值：" << (numeric_limits<long double>::max)();
    cout << "\t最小值：" << (numeric_limits<long double>::min)() << endl;
    cout << "float: \t\t" << "所占字节数：" << sizeof(float);
    cout << "\t最大值：" << (numeric_limits<float>::max)();
    cout << "\t最小值：" << (numeric_limits<float>::min)() << endl;
    cout << "size_t: \t" << "所占字节数：" << sizeof(size_t);
    cout << "\t最大值：" << (numeric_limits<size_t>::max)();
    cout << "\t最小值：" << (numeric_limits<size_t>::min)() << endl;
    cout << "string: \t" << "所占字节数：" << sizeof(string) << endl;
    // << "\t最大值：" << (numeric_limits<string>::max)() << "\t最小值：" << (numeric_limits<string>::min)() << endl;  
    cout << "type: \t\t" << "************size**************" << endl;

    system("pause");
    return 0;
}

2. Linux system

2.1 32-bit compiler

32位 Linux上的数据类型与范围
type:           ************size**************
bool:           所占字节数：1   最大值：1               最小值：0
char:           所占字节数：1   最大值：Del            最小值：€
signed char:    所占字节数：1   最大值：Del            最小值：€
unsigned char:  所占字节数：1   最大值：255             最小值：0
wchar_t:        所占字节数：2   最大值：65535           最小值：0
short:          所占字节数：2   最大值：32767           最小值：-32768
int:            所占字节数：4   最大值：2147483647      最小值：-2147483648
unsigned:       所占字节数：4   最大值：4294967295      最小值：0
long:           所占字节数：4   最大值：2147483647      最小值：-2147483648
unsigned long:  所占字节数：4   最大值：4294967295      最小值：0
double:         所占字节数：8   最大值：1.79769e+308    最小值：2.22507e-308
long double:    所占字节数：8   最大值：1.79769e+308    最小值：2.22507e-308
float:          所占字节数：4   最大值：3.40282e+38     最小值：1.17549e-38
size_t:         所占字节数：4   最大值：4294967295      最小值：0
string:         所占字节数：28

2.2 64-bit compiler

64位 Linux上的数据类型与范围

type:           ************size**************
bool:           所占字节数：1   最大值：1                     最小值：0
char:           所占字节数：1   最大值：DEL                  最小值：€
signed char:    所占字节数：1   最大值：DEL                  最小值：€
unsigned char:  所占字节数：1   最大值：255                   最小值：0
wchar_t:        所占字节数：2   最大值：65535                 最小值：0
short:          所占字节数：2   最大值：32767                 最小值：-32768
int:            所占字节数：4   最大值：2147483647            最小值：-2147483648
unsigned:       所占字节数：4   最大值：4294967295            最小值：0
long:           所占字节数：8   最大值：9223372036854775807   最小值：-9223372036854775807
unsigned long:  所占字节数：8   最大值：18446744073709551615  最小值：0
double:         所占字节数：8   最大值：1.79769e+308          最小值：2.22507e-308
long double:    所占字节数：8   最大值：1.79769e+308          最小值：2.22507e-308
float:          所占字节数：4   最大值：3.40282e+38           最小值：1.17549e-38
size_t:         所占字节数：8   最大值：18446744073709551615  最小值：0
string:         所占字节数：40
type:           ************size**************

3. Out of bounds and overflow

When the value of the variable exceeds its maximum value, if you add 1, it will go out of bounds, and the variable will change from the maximum value to the minimum value, that is, MAX+1 → MIN, here the maximum value of long and int on Windows 64 bits Take crossing the boundary as an example for explanation.
The maximum values of long and int are both 2147483647. If you add 1, it will go out of bounds and directly become the minimum value -2147483648, as shown in the chart (1):

Table (1) Data overflow and underflow

	Max	Max+1(overflow)	Minimum valueMin	Min-1 (underflow)
bool	1	1	0	1
char	127	-128	-128	127
signed char	127	-128	-128	127
unsigned char	255	0	0	255
wchar_t	65535	0	0	65535
short	32767	-32768	-32768	32767
int	2147483647	-2147483648	-2147483648	2147483647
unsigned	4294967295	0	0	4294967295
long	2147483647	-2147483648	-2147483648	2147483647
unsigned long	4294967295	0	0	4294967295

Note that bool is represented by unsigned int in C++, so adding 1 to the maximum value of bool will not overflow (1+1 < 4294967295), and the overflow will become 0 (1+ 4294967295 overflows and becomes 0).

//LongMax.cpp

#include<iostream>  
#include <limits>

using namespace std;

#pragma warning(disable:4804) 
#pragma warning(disable:4146) 

void LongMax()
{
    
    
    cout << "bool: \t\t" << "所占字节数：" << sizeof(bool);
    cout << "\t最大值：" << (numeric_limits<bool>::max)();
    cout << "\t\t最小值：" << (numeric_limits<bool>::min)() << endl;
    cout << "char: \t\t" << "所占字节数：" << sizeof(char);
    cout << "\t最大值：" << (int)(numeric_limits<char>::max)();
    cout << "\t\t最小值：" << (int)(numeric_limits<char>::min)() << endl;
    cout << "signed char: \t" << "所占字节数：" << sizeof(signed char);
    cout << "\t最大值：" << (int)(numeric_limits<signed char>::max)();
    cout << "\t\t最小值：" << (int)(numeric_limits<signed char>::min)() << endl;
    cout << "unsigned char: \t" << "所占字节数：" << sizeof(unsigned char);
    cout << "\t最大值：" << (int)(numeric_limits<unsigned char>::max)();
    cout << "\t\t最小值：" << (int)(numeric_limits<unsigned char>::min)() << endl;
    cout << "short: \t\t" << "所占字节数：" << sizeof(short);
    cout << "\t最大值：" << (numeric_limits<short>::max)();
    cout << "\t\t最小值：" << (numeric_limits<short>::min)() << endl;
    cout << "int: \t\t" << "所占字节数：" << sizeof(int);
    cout << "\t最大值：" << (numeric_limits<int>::max)();
    cout << "\t最小值：" << (numeric_limits<int>::min)() << endl;
    cout << "unsigned int:\t" << "所占字节数：" << sizeof(unsigned int);
    cout << "\t最大值：" << (numeric_limits<unsigned>::max)();
    cout << "\t最小值：" << (numeric_limits<unsigned>::min)() << endl;
    cout << "long: \t\t" << "所占字节数：" << sizeof(long);
    cout << "\t最大值：" << (numeric_limits<long>::max)();
    cout << "\t最小值：" << (numeric_limits<long>::min)() << endl;
    cout << "unsigned long: \t" << "所占字节数：" << sizeof(unsigned long);
    cout << "\t最大值：" << (numeric_limits<unsigned long>::max)();
    cout << "\t最小值：" << (numeric_limits<unsigned long>::min)() << endl;
    cout << "type: \t\t" << "************size**************" << endl<<endl;
}

//上溢出
void MaxAddOne()
{
    
    
    bool boolA = 1;
    cout << "before boolA= " << boolA << endl;
    boolA += 4294967295;
    cout << "after  boolA= " << boolA << endl << endl;

    char charB = 127;
    cout << "before charB= " << (int)charB << endl;
    charB += 1;
    cout << "after  charB= " << (int)charB << endl << endl;

    signed char sigCharC = 127;
    cout << "before  signed sigCharC= " << (int)sigCharC << endl;
    sigCharC += 1;
    cout << "after   signed sigCharC= " << (int)sigCharC << endl << endl;

    unsigned char unsigCharD = 255;
    cout << "before  unsigned unsigCharD= " << (int)unsigCharD << endl;
    unsigCharD += 1;
    cout << "after   unsigned unsigCharD= " << (int)unsigCharD << endl << endl;

    wchar_t wchar_tE = 65535;
    cout << "before  wchar_t wchar_tE= " << wchar_tE << endl;
    wchar_tE += 1;
    cout << "after   wchar_t wchar_tE= " << wchar_tE << endl << endl;

    int intF = 2147483647;
    cout << "before  int intF= " << intF << endl;
    intF += 1;
    cout << "after   int intF= " << intF << endl << endl;

    unsigned unsigIntG = 4294967295;
    cout << "before  unsigned unisigndG= " << unsigIntG << endl;
    unsigIntG += 1;
    cout << "after   unsigned unisigndG= " << unsigIntG << endl << endl;

    long longH = 2147483647;
    cout << "before  long longH= " << longH << endl;
    longH += 1;
    cout << "after   long longH= " << longH << endl << endl;

    unsigned long unsigLongI = 4294967295;
    cout << "before unsigned long unsigLongI= " << unsigLongI << endl;
    unsigLongI += 1;
    cout << "after  unsigned long unsigLongI= " << unsigLongI << endl << endl;
}

//下溢出  
void MinSubOne()
{
    
    
    bool boolA = 0;
    cout << "before boolA= " << boolA << endl;
    boolA -= 1;
    cout << "after  boolA= " << boolA << endl << endl;

    char charB =-128;
    cout << "before charB= " << (int)charB << endl;
    charB -= 1;
    cout << "after  charB= " << (int)charB << endl << endl;

    signed char sigCharC = -128;
    cout << "before  signed sigCharC= " << (int)sigCharC << endl;
    sigCharC -= 1;
    cout << "after   signed sigCharC= " << (int)sigCharC << endl << endl;

    unsigned char unsigCharD = 0;
    cout << "before  unsigned unsigCharD= " << (int)unsigCharD << endl;
    unsigCharD -= 1;
    cout << "after   unsigned unsigCharD= " << (int)unsigCharD << endl << endl;

    wchar_t wchar_tE = 0;
    cout << "before  wchar_t wchar_tE= " << wchar_tE << endl;
    wchar_tE -= 1;
    cout << "after   wchar_t wchar_tE= " << wchar_tE << endl << endl;

    int intF = -2147483648;
    cout << "before  int intF= " << intF << endl;
    intF -= 1;
    cout << "after   int intF= " << intF << endl << endl;

    unsigned unsigIntG = 0;
    cout << "before  unsigned unisigndG= " << unsigIntG << endl;
    unsigIntG -= 1;
    cout << "after   unsigned unisigndG= " << unsigIntG << endl << endl;

    long longH = -2147483648;
    cout << "before  long longH= " << longH << endl;
    longH -= 1;
    cout << "after   long longH= " << longH << endl << endl;

    unsigned long unsigLongI = 0;
    cout << "before unsigned long unsigLongI= " << unsigLongI << endl;
    unsigLongI -= 1;
    cout << "after  unsigned long unsigLongI= " << unsigLongI << endl << endl;
}

int main()
{
    
    
    //上溢出
    cout << "--------------------(1)上溢出--------------------" << endl;
    MaxAddOne();

    //下溢出
    cout << "--------------------(2)下溢出--------------------" << endl;
    MinSubOne();
            
    system("pause");
    return 0;
}

The effect is as follows:

Figure (1) The minimum value is obtained by overflow, and the maximum value is obtained by underflow