分支语句

#include
    
     using namespace std;/*int main() {	char ch;	int spaces = 0;	int total = 0;	cin.get(ch);	while (ch != '.') {		if (ch == ' ') {			spaces++;		}		total++;		cin.get(ch);		//联系5.8练习题		//循环内继续读取输入以判定结束标志	}	cout << spaces << " spaces, " << total;	cout << " characters total in sentence\n";	return 0;}*//*//if-else结构int main() {	char ch;	cout << "Type, and I shall repeat.\n";	cin.get(ch);	while (ch != '.') {		if (ch == '\n') {			cout << ch;		}		else {			//cout << ++ch;			cout << ch + 1;			//ch+1结果被提升为int型		}		cin.get(ch);	}	cout << "\nPlease excuse the slight confusion.\n";	return 0;}*///else之后也可以是语句块//也可以继续添加if-else//整个结构被视为一条语句/*const int Fave = 27;int main() {	int n;	cout << "Enter a number in the range 1-100 to find ";	cout << "my favorite number: ";	do {		cin >> n;		if (n < Fave) {			cout << "Too low _____ guess again: ";		}		else if (n > Fave) {			cout << "Too high _____ guess again: ";		}		else {			cout << Fave << " is right!";		}	} while (n != Fave);	return 0;}*///switch/*void showmenu();void report();void comfort();int main() {	showmenu();	int choice;	cin >> choice;	while (choice != 5) {		switch (choice) {			case 1:cout << "\a\n";				break;			case 2:report();				break;			case 3:cout << "The boss was in all day.\n";				break;			case 4:comfort();				break;			default:cout << "That's not a choice.\n";		}		showmenu();		cin >> choice;	}	cout << "Bye!\n";	return 0;}void showmenu() {	cout << "Please enter 1, 2, 3, 4, or 5:\n1)alarm		2)report\n3)alibi		4)comfort\n"		"5)quit\n";}void report() {	cout << "It's been an excellent week for business.\n"		"Sales are up 120%. Expenses are down 35%.\n";}void comfort() {	cout << "Your employees think you are the finest CEO\n"		"in the industry. The board of directors think\n"		"you are the finest CEO in the industry.\n";}*///switch case接受的类型必须是整数常量，int\char,或枚举量//break表示终止循环，没有break将会继续检测/*enum { red, orange, yellow, green, blue, violet, indigo };int main() {	cout << "Enter color code(0-6): ";	int code;	cin >> code;	while (code >= red && code <= indigo) {		switch (code) {		case red:cout << "Her lios were red.\n"; break;		case orange:cout << "Her hair was orange.\n"; break;		case yellow:cout << "Her shoes were yellow.\n"; break;		case green:cout << "Her nails were green.\n"; break;		case blue:cout << "Her sweatsuit was blue.\n"; break;		case violet:cout << "Her eyes were violet.\n"; break;		case indigo:cout << "Her mood was indigo.\n"; break;		}		cout << "Enter color code(0-6): ";		cin >> code;	}	cout << "Bye\n";	return 0;}*///当选项全为常量且不少于3个时，switch效率高于ifelse//数字循环/*const int Max = 5;int main() {	int golf[Max];	cout << "Please enter your golf scores.\n";	cout << "You must enter " << Max << " rounds.\n";	int i;	for (i = 0; i < Max; i++) {		cout << "round #" << i + 1 << ": ";		while (!(cin >> golf[i])) {			cin.clear();			while (cin.get() != '\n') {				continue;				//会回跳至整个循环的开头				//而非上一级			}			cout << "Please enter a number: ";		}	}	double total = 0.0;	for (i = 0; i < Max; i++) {		total += golf[i];	}	cout << total / Max << " = average score " << Max << " rounds\n";	return 0;}*/
    

初识文件写入读取

//文件输入输出//与iostream不同，文建输出必须声明自己的ofstream对象(cout)#include
    
     /*int main() {	char automobile[50];	int year;	double a_price;	double b_price;	ofstream outFile;	outFile.open("carinfo.txt");	//如果没有，会自动新建	//如果存在，会清空原内容	cout << "Enter the make and model of automobile: ";	cin.getline(automobile, 50);	cout << "Enter the model year: ";	cin >> year;	cout << "Enter the original asking price: ";	cin >> a_price;	b_price = 0.913*a_price;	cout << fixed;	//用一般的方式输出浮点数,而不是科学计数法	cout.precision(2);	//数据精度	cout.setf(ios_base::showpoint);	//显示浮点数小数点后面的零	cout << "Make and model: " << automobile << endl;	cout << "Year: " << year << endl;	cout << "Was asking $" << a_price << endl;	cout << "Now asking $" << b_price << endl;	//cout可替换为outFile	//outFile<
     
      #include
      
       const int SIZE = 60;int main() {	char filename[SIZE];	ifstream inFile;	cout << "Enter the name of data file: ";	cin.getline(filename, SIZE);	inFile.open(filename);	if (!inFile.is_open()) {		cout << "Could not open the file " << filename << endl;		cout << "Program terminating.\n";		exit(EXIT_FAILURE);	}	double value;	double sum = 0.0;	int count = 0;	inFile >> value;	while (inFile.good()) {		++count;		sum += value;		inFile >> value;	}	if (inFile.eof()) {		cout << "End of file reached.\n";	}	else if (inFile.fail()) {		cout << "Input terminated by data mismatch.\n";	}	else {		cout << "Items read: " << count << endl;		cout << "Sum: " << sum << endl;		cout << "Average: " << sum / count << endl;	}	inFile.close();	return 0;}
      
     
    

逻辑运算符

#include
    
     using namespace std;//or/*int main() {	cout << "This program may re format your hard disk\n"		"and destroy all your data.\n"		"Do you still wish to continue?
     
      ";	char ch;	cin.get(ch);	if (ch == 'y' || ch == 'Y') {		cout << "You were warned!\a\a\n";	}	else if (ch == 'n' || ch == 'N') {		cout << "Good dog.\n";	}	else {		cout << "That's wasn't a y or n!Apparently you "			"can't follw\ninstructions,so "			"I'll trash your disk anyway\a\a\a\n";	}	return 0;}*///and/*const int ArSize = 6;int main() {	float naaq[ArSize];	cout << "Enter the NAAQs(New Age Awareness Quotients) "		"of\nyour neighbors Program terminates "		"when you make\n" << ArSize << " enteries "		"or enter a negative value.\n";	int i = 0;	float temp;	cout << "First value: ";	cin >> temp;	while (i < ArSize&&temp >= 0) {		naaq[i] = temp;		++i;		if (i < ArSize) {			cout << "Next value: ";			cin >> temp;		}	}	if (i == 0) {		cout << "No data - -bye\n";	}	else {		cout << "Enter your NAAQ: ";		float you;		cin >> you;		int count = 0;		for (int j = 0; j < i; j++) {			if (naaq[j] > you) {				++count;			}		}		cout << count << " of your neighbors have greater awareness of\n"			"the New Age than you do.\n";	}1	return 0;}*//*int main() {	int a, b;	cout << "Enter 2 integers: ";	cin >> a>>b;	cout << "The larger of " << a << " and " << b;	int c = a > b ? a : b;	等效	int c;	if(a>b){c=a;}	else{c=b;}	cout << " is " << c << endl;	return 0;}*/