C/C++中各種類型int、long、double、char表示範圍(最大最小值)

#include<iostream>
#include<string>
#include <limits>
using namespace std;

int main()
{
    cout << "type: \t\t" << "************size**************"<< endl;
    cout << "bool: \t\t" << "所佔字節數:" << 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" << "所佔字節數:" << sizeof(char);
    cout << "\t最大值:" << (numeric_limits<char>::max)();
    cout << "\t\t最小值:" << (numeric_limits<char>::min)() << endl;
    cout << "signed char: \t" << "所佔字節數:" << sizeof(signed char);
    cout << "\t最大值:" << (numeric_limits<signed char>::max)();
    cout << "\t\t最小值:" << (numeric_limits<signed char>::min)() << endl;
    cout << "unsigned char: \t" << "所佔字節數:" << sizeof(unsigned char);
    cout << "\t最大值:" << (numeric_limits<unsigned char>::max)();
    cout << "\t\t最小值:" << (numeric_limits<unsigned char>::min)() << endl;
    cout << "wchar_t: \t" << "所佔字節數:" << 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" << "所佔字節數:" << 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" << "所佔字節數:" << sizeof(int);
    cout << "\t最大值:" << (numeric_limits<int>::max)();
    cout << "\t最小值:" << (numeric_limits<int>::min)() << endl;
    cout << "unsigned: \t" << "所佔字節數:" << 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" << "所佔字節數:" << 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" << "所佔字節數:" << 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" << "所佔字節數:" << 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" << "所佔字節數:" << 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" << "所佔字節數:" << 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" << "所佔字節數:" << 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" << "所佔字節數:" << 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;
    return 0;
}



/*運行結果分析:

以上結果已經很明白了,一下補充說明幾點:

概念、整型:表示整數、字符和布爾值的算術類型合稱爲整型(integral type)

關於帶符號與無符號類型:整型 int、stort  和  long 都默認爲帶符號型。要獲得無符號型則必須制定該類型爲unsigned,比如unsigned long。unsigned int類型可以簡寫爲unsigned,也就是說,unsigned後不加其他類型說明符就意味着是unsigned int。

一字節表示八位,即:1byte = 8 bit;

int: 4byte =  32 bit 有符號signed範圍:2^31-1 ~ -2^31即:2147483647 ~ -2147483648無符號unsigned範圍:2^32-1 ~ 0即:4294967295 ~ 0

long: 4 byte = 32 bit 同int型

double: 8 byte = 64 bit 範圍:1.79769e+308 ~ 2.22507e-308

long double: 12 byte = 96 bit 範圍: 1.18973e+4932 ~ 3.3621e-4932

float: 4 byte = 32 bit 範圍: 3.40282e+038 ~ 1.17549e-038

int、unsigned、long、unsigned long 、double的數量級最大都只能表示爲10億,即它們表示十進制的位數不超過10個,即可以保存所有9位整數。而short只是能表示5位;


另外對於浮點說而言:使用double類型基本上不會有錯。在float類型中隱式的精度損失是不能忽視的,二雙精度計算的代價相對於單精度可以忽略。事實上,在有些機器上,double類型比float類型的計算要快得多。float型只能保證6位有效數字,而double型至少可以保證15位有效數字(小數點後的數位),long double型提供的精度通常沒有必要,而且還要承擔額外的運行代價。

double是8字節共64位,其中小數位佔52位,2-^52=2.2204460492503130808472633361816e-16,量級爲10^-16,故能夠保證2^-15的所有精度。

在有些機器上,用long類型進行計算所付出的運行時代價遠遠高於用int類型進行同樣計算的代價,所以算則類型前要先了解程序的細節並且比較long類型與int類型的實際運行時性能代價。



歡迎提出寶貴意見,以幫助我改進,不勝感激!!!

——桑海整理

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