C++ Primer plus 第三章

本文通过多个C++代码示例,介绍了整数类型的不同进制表示、字符与ASCII码的关系、浮点运算的特点及类型转换的方法等内容。

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3.1 limits.cpp

代码

#include <iostream>
#include <climits>

using namespace std;

int main()
{
	int n_int = INT_MAX;
	short n_short = SHRT_MAX;
	long n_long = LONG_MAX;
	long long n_llong = LLONG_MAX;

	cout << "int is " << sizeof(int) << " bytes." << endl;
	cout << "short is " << sizeof n_short << " bytes." << endl;
	cout << "long is " << sizeof n_long << " bytes." << endl;
	cout << "long long is " << sizeof n_llong << "bytes." << endl;
	cout << endl;

	cout << "Maximun values:" << endl;
	cout << "int:" << n_int << endl;
	cout << "short: " << n_short << endl;
	cout << "long: " << n_long << endl;
	cout << "long long: " << n_llong << endl << endl;

	cout << "Minimun int value = " << INT_MIN << endl;
	cout << "Bits per bytes = " << CHAR_BIT << endl;

	return 0;
}

结果

在这里插入图片描述

知识点

1.sizeof用法
2.头文件climits
3.变量初始化(声明+赋值)

3.2exceed.cpp

代码

#include <iostream>
#include <climits>

#define ZERO 0;

using namespace std;

int main()
{
	short sam = SHRT_MAX;
	unsigned short sue = sam;
	cout << "Sam has " << sam << " dollars and Sue has " << sue;
	cout << " dollars deposited." << endl
		<< "Add $1 to each account." << endl << "Now ";

	sam = sam + 1;
	sue = sue + 1;
	cout << "Sam has " << sam << " dollars and Sue has " << sue;
	cout << " dollars deposited.\nPoor Sam!" << endl;

	sam = ZERO;
	sue = ZERO;
	cout << "Sam has " << sam << " dollars and Sue has " << sue;
	cout << " dollars deposited." << endl;
	cout << "Take $1 from each account." << endl << "Now ";

	sam = sam - 1;
	sue = sue - 1;
	cout << "Sam has " << sam << " dollars and Sue has " << sue;
	cout << " dollars deposited." << endl << "Lucky Sue!" << endl;

	return 0;
}

结果

在这里插入图片描述

知识点

1.无符号类型变量的定义
2.超过变量类型的范围将导致溢出
short类型变量sam最大数值为SHRT_MAX,加上1后超出范围,结果为-32768。
unsigned short类型sue最小数值为0,减去1后超出范围,结果为65535。

3.3 hexoct.cpp

代码

#include <iostream>

using namespace std;

int main()
{
	int chest = 42;
	int waist = 0x42;
	int inseam = 024;

	cout << "Monsieur cuts a striking figure!\n";
	cout << "chest = " << chest << "{42 in decimal}\n";
	cout << "waist = " << waist << "{0x42 in hex}\n";
	cout << "inseam = " << inseam << "{042 in octal}\n";

	return 0;
}

结果

在这里插入图片描述

知识点

  1. 整数类型的十进制、十六进制、八进制的定义
  2. \n与endl相同功能(换行)

3.4 hexoct2.cpp

代码

#include <iostream>

using namespace std;

int main()
{
	int chest = 42;
	int waist = 42;
	int inseam = 42;

	cout << "Monsieur cuts a striking figure!" << endl;
	cout << "chest = " << chest << "{decimal for 42}" << endl;
	cout << hex;
	cout << "waist = " << waist << "{hexadecimal for 42}" << endl;
	cout << oct;
	cout << "inseam = " << inseam << "{octal for 42}" << endl;

	return 0;
}

结果

在这里插入图片描述

知识点

1.整数类型的十进制、十六进制、八进制的显示

cout << hex;//不显示在屏幕中,但修改了cout显示的方式

3.5 chartype.cpp

代码

#include <iostream>

using namespace std;

int main()
{
	char ch;

	cout << "Enter a character: " << endl;
	cin >> ch;
	cout << "Hola! ";
	cout << "Thank you for the " << ch << " character." << endl;

	return 0;
}

结果

在这里插入图片描述

知识点

1.字符型变量的声明,输入和输出。

3.6 morechar.cpp

代码

#include <iostream>

using namespace std;

int main()
{
	char ch = 'M';
	int i = ch;
	cout << "The ASCII code for " << ch << " is " << i << endl;

	cout << "Add one to the character code:" << endl;
	ch = ch + 1;
	i = ch;
	cout << "The ASCII code for " << ch << " is " << i << endl;

	cout << "Displaying char ch using cout.put(ch): ";
	cout.put(ch);

	cout.put('!');
	cout << endl << "Done" << endl;

	return 0;
}

结果

在这里插入图片描述

知识点

1.char类型变量的初始化
2.char类型实际上是int类型,可以对其整数的运算,如+
3.cout.put()函数输出字符

3.7 bondini.cpp

代码

#include <iostream>

using namespace std;

int main()
{
	cout << "\aOperation \"HyperHype\" is now activated!\n";
	cout << "Enter your agent code:_________\b\b\b\b\b\b\b\b";
	long code;
	cin >> code;
	cout << "\aYou entered " << code << "...\n";
	cout << "\aCode verified! Proceed with Plan z3!\n";

	return 0;
}

结果

在这里插入图片描述

知识点

1.转义字符的使用\a、"、\n等等

3.8 floatnum.cpp

代码

#include<iostream>

using namespace std;

int main()
{
	cout.setf(ios_base::fixed, ios_base::floatfield);

	float tub = 10.0 / 3.0;
	double mint = 10.0 / 3.0;
	const float million = 1.0e6;

	cout << "tub = " << tub;
	cout << ", a million tubs = " << million * tub;
	cout << ", \nand ten million tubs = ";
	cout << 10 * million*tub << endl;

	cout << "mint = " << mint << " and a million mints = ";
	cout << million * mint << endl;

	return 0;
}

结果

在这里插入图片描述

知识点

1.cout.setf()函数让cout后面显示出全部内容,一般情况下没有该函数时,多余的0不会显示出来。
2.float、double等浮点型数据的定义。
3.精度限制

3.9 fltadd.cpp

代码

#include <iostream>

using namespace std;

int main()
{
	float a = 2.34E+22f;
	float b = a + 1.0f;

	cout << "a = " << a << endl;
	cout << "b - a = " << b - a << endl;

	return 0;
}

结果

在这里插入图片描述

知识点

1.浮点运算的速度比整型慢,且精度比整型低

b = a + 1.0f;

但是

b - a = 0

说明了精度低。

3.10 arith.cpp

代码

#include <iostream>

using namespace std;

int main()
{
	float hats, heads;

	cout.setf(ios_base::fixed, ios_base::floatfield);

	cout << "Enter a number: ";
	cin >> hats;
	cout << "Enter another number: ";
	cin >> heads;

	cout << "hats = " << hats << "; heads = " << heads << endl;
	cout << "hats + heads = " << hats + heads << endl;
	cout << "hats - heads = " << hats - heads << endl; 
	cout << "hats * heads = " << hats * heads << endl;
	cout << "hats / heads = " << hats / heads << endl;

	return 0;
}

结果

在这里插入图片描述

知识点

1.基本运算+ - * /

3.11 divide.cpp

代码

#include <iostream>

using namespace std;

int main()
{
	cout.setf(ios_base::fixed, ios_base::floatfield);

	cout << "Integer division: 9/5 = " << 9 / 5 << endl;

	cout << "Floating-point division: 9.0/5.0 = ";
	cout << 9.0 / 5.0 << endl;

	cout << "Mixed division: 9.0 / 5  = " << 9.0 / 5 << endl;

	cout << "double constants: 1e7/9.0 = ";
	cout << 1.e7 / 9.0 << endl;

	cout << "float constants: 1e7f/9.0f = ";
	cout << 1.e7f / 9.0f << endl;


	return 0;
}

结果

在这里插入图片描述

知识点

1.不同类型的数据、混合的数据之间的除法
2.重载:函数相同,输入不同(除法的输入可以是各种类型数据)

3.12 modulus.cpp

代码

#include <iostream>

using namespace std;

int main()
{
	const int Lbs_per_stn = 14;
	int lbs;

	cout << "Enter your weight in pounds: ";
	cin >> lbs;
	int stone = lbs / Lbs_per_stn;
	int pounds = lbs % Lbs_per_stn;
	cout << lbs << " pounds are " << stone
		<< " stone, " << pounds << " pound(s).\n";

	return 0;
}

结果

在这里插入图片描述

知识点

1.取余%

3.13 assign.cpp

代码

#include <iostream>

using namespace std;

int main()
{
	cout.setf(ios_base::fixed, ios_base::floatfield);

	float tree = 3;
	int guess(3.9832);
	int debt = 7.2E12;

	cout << "tree = " << tree << endl;
	cout << "guess = " << guess << endl;
	cout << "debt = " << debt << endl;

	return 0;
}

结果

在这里插入图片描述

知识点

1.类型转换

3.14 typecast.cpp

代码

#include <iostream>

using namespace std;

int main()
{
	int auks, bats, coots;

	auks = 19.99 + 11.99;

	bats = (int)19.99 + (int)11.99;
	coots = int(19.99) + int(11.99);
	cout << "auks = " << auks << ", bats = " << bats;
	cout << ", coots = " << coots << endl;

	char ch = 'Z';
	cout << "The code for " << ch << " is ";
	cout << int(ch) << endl;
	cout << "Yes, the code is ";
	cout << static_cast<int>(ch) << endl;


	return 0;
}

结果

在这里插入图片描述

知识点

1.强制类型转换,如int(float)
2.static_cast(ch)用法

总结

长路漫漫!!!

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