1. C++ Control Structures 程式的控制、運算、判斷跟你之前學過的程式語言是類 似的，所以這裡我們只用程式碼來說明。 你應該而且必須能看得懂這些程式 !!

2. // Fig. 1.2: fig01_02.cpp // A first program in C++ #include int main() { std::cout << "Welcome to C++!\n"; return 0; // indicate that program ended successfully } 你能回答這些問題嗎 ? // 是做什麼用的 什麼是 #include? 什麼是 iostream? 什麼是 std? cout? \n?

3. // Printing a line with multiple statements #include using std::cout; int main() { cout << "Welcome "; cout << "to C++!\n"; return 0; // indicate that program ended successfully } 你能回答這些問題嗎 ? 什麼是 using std::cout? 為什麼 main( ) 裡的 cout 前不加 std:: ? 這個 program 的 output 是什麼 ?

4. // Printing multiple lines with a single statement #include Using namespace std; int main() { cout << "Welcome\nto\n\nC++!“<< endl; return 0; // indicate that program ended successfully } 你能回答這些問題嗎 ? 什麼是 using namespace std? 什麼是 endl? 這個 program 的 output 是什麼 ?

5. // Fig. 1.6: fig01_06.cpp Addition program #include int main() { int integer1, integer2, sum; // declaration std::cout << "Enter first integer\n"; // prompt std::cin >> integer1; // read an integer std::cout << "Enter second integer\n"; // prompt std::cin >> integer2; // read an integer sum = integer1 + integer2; // assignment of sum std::cout << "Sum is " << sum << std::endl; // print sum return 0; // indicate that program ended successfully } 你能回答這些問題嗎 ? 什麼是 cin?

6. // Fig. 1.14: fig01_14.cpp //Using if statements, relational operators, and equality operators #include using std::cout; using std::cin; using std::endl; int main() { int num1, num2; cout << "Enter two integers, and I will tell you\n" << "the relationships they satisfy: "; cin >> num1 >> num2; // read two integers if ( num1 == num2 ) cout << num1 << " is equal to " << num2 << endl; 你能回答這些問題嗎 ? 你知道這些邏輯判斷代表的意思嗎 ? = = != >= 它們應該用在什麼地方 ?

7. if ( num1 != num2 ) cout << num1 << " is not equal to " << num2 << endl; if ( num1 < num2 ) cout << num1 << " is less than " << num2 << endl; if ( num1 > num2 ) cout << num1 << " is greater than " << num2 << endl; if ( num1 <= num2 ) cout << num1 << " is less than or equal to " << num2 << endl; if ( num1 >= num2 ) cout << num1 << " is greater than or equal to " << num2 << endl; return 0; // indicate that program ended successfully }

8. //Fig. 2.14: fig02_14.cpp Preincrementing and postincrementing #include using std::cout; using std::endl; int main() { int c; c = 5; cout << c << endl; // print 5 cout << c++ << endl; // print 5 then postincrement cout << c << endl << endl; // print 6 c = 5; cout << c << endl; // print 5 cout << ++c << endl; // preincrement then print 6 cout << c << endl; // print 6 return 0; // successful termination } 你能回答這些問題嗎 ? cout << c++; 跟 cout << ++c; 有何不同 ?

9. // Fig. 2.7: fig02_07.cpp //Class average program with counter-controlled repetition #include using std::cout; using std::cin; using std::endl; int main() { int total, // sum of grades gradeCounter, // number of grades entered grade, // one grade average; // average of grades // initialization phase total = 0; // clear total gradeCounter = 1; // prepare to loop 如何寫一個 while loop? 1. 變數及 data 的宣告與初始化 while( 2. 變數的判斷 ) { 3. 處理資料 4. 變數的改變 }

10. // processing phase while ( gradeCounter <= 10 ) { // loop 10 times cout << "Enter grade: "; // prompt for input cin >> grade; // input grade total = total + grade; // add grade to total gradeCounter = gradeCounter + 1; // increment counter } // termination phase average = total / 10; // integer division cout << "Class average is " << average << endl; return 0; // indicate program ended successfully } 你能回答這些問題嗎 ? x = x + 1 在 C++ 裡是什麼意思 ?

11. // Fig. 2.17: fig02_17.cpp // Counter-controlled repetition with the for structure #include using std::cout; using std::endl; int main() { // Initialization, repetition condition, and incrementing // are all included in the for structure header. for ( int counter = 1; counter <= 10; counter++ ) cout << counter << endl; return 0; } 如何寫一個 for loop? data 的宣告與初始化 for( 1. 變數宣告初始化 ; 2. 變數的判斷 ; 4. 變數的改變 ) { 3. 處理 data }

12. // Fig. 2.20: fig02_20.cpp Summation with for #include using std::cout; using std::endl; int main() { int sum = 0; for ( int number = 2; number <= 100; number += 2 ) sum += number; cout << "Sum is " << sum << endl; return 0; }

13. // Fig. 2.24: fig02_24.cpp // Using the do/while repetition structure #include using std::cout; using std::endl; int main() { int counter = 1; do { cout << counter << " "; } while ( ++counter <= 10 ); cout << endl; return 0; } 如何寫一個 do/while loop? 1. 變數及 data 的宣告與初始化 do{ 2. 處理 data 3. 變數的改變 } while( 4. 變數的判斷 ); 或 1. 變數及 data 的宣告與初始化 do{ 2. 處理 data } while(3. 變數的改變 4. 變數的判斷 );

14. 你能回答這些問題嗎 ? 你知道什麼時候該用 while 什麼時候該用 do/while 什麼時候該用 for 嗎 ?

15. // Fig. 2.21: fig02_21.cpp Calculating compound interest #include using std::cout; using std::endl; using std::ios; #include using std::setw; using std::setiosflags; using std::setprecision; #include int main() { double amount, // amount on deposit principal = 1000.0, // starting principal rate =.05; // interest rate 利用 iomanip 中的 setw setioflags setprecision 來編排資料的格式 利用 cmath library 中的 pow 來計算 數字的 power

16. cout << "Year" << setw( 21 ) << "Amount on deposit" << endl; // set the floating-point number format cout << setiosflags( ios::fixed | ios::showpoint ) << setprecision( 2 ); for ( int year = 1; year <= 10; year++ ) { amount = principal * pow( 1.0 + rate, year ); cout << setw( 4 ) << year << setw( 21 ) << amount << endl; } return 0; }

17. // Fig. 2.22: fig02_22.cpp Counting letter grades #include using std::cout; using std::cin; using std::endl; int main() { int grade, // one grade aCount = 0, // number of A's bCount = 0, // number of B's cCount = 0, // number of C's dCount = 0, // number of D's fCount = 0; // number of F's cout << "Enter the letter grades." << endl << "Enter the EOF character to end input." << endl;

18. while ( ( grade = cin.get() ) != EOF ) { switch ( grade ) { // switch nested in while case 'A': // grade was uppercase A case 'a': // or lowercase a ++aCount; break; // necessary to exit switch case 'B': // grade was uppercase B case 'b': ++bCount; // or lowercase b break; case 'C': // grade was uppercase C case 'c': ++cCount; // or lowercase c break; case 'D': // grade was uppercase D case 'd': ++dCount; // or lowercase d break;

19. case 'F': // grade was uppercase F case 'f': ++fCount; // or lowercase f break; case '\n': case '\t': // ignore newlines and tabs, case ' ': break; // and spaces in input default: // catch all other characters cout << "Incorrect letter grade entered." << " Enter a new grade." << endl; break; // optional } cout << "\n\nTotals for each letter grade are:" << "\nA: " << aCount << "\nB: " << bCount << "\nC: " << cCount << "\nD: " << dCount << "\nF: " << fCount << endl; return 0; }

20. 你能回答這些問題嗎 ? 你知道什麼時候該用 if/else 什麼時候該用 switch 嗎 ? 你知道 “ ? : “ 這個運算怎麼用嗎 ?

21. // Fig. 2.26: fig02_26.cpp // Using the break statement in a for structure #include using std::cout; using std::endl; int main() { int x; // x declared here so it can be used after the loop for ( x = 1; x <= 10; x++ ) { if ( x == 5 ) break; // break loop only if x is 5 cout << x << " "; } cout << "\nBroke out of loop at x of " << x << endl; return 0; }

22. // Fig. 2.27: fig02_07.cpp // Using the continue statement in a for structure #include using std::cout; using std::endl; int main() { for ( int x = 1; x <= 10; x++ ) { if ( x == 5 ) continue; // skip remaining code in loop // only if x is 5 cout << x << " "; } cout << "\nUsed continue to skip printing the value 5" << endl; return 0; }