1 Lecture 04 Structural Programming in C++ You will learn: i) Operators: relational and logical ii) Conditional statements iii) Repetitive statements iv) Functions and passing parameter v) Structures

2/22 Structural Programming in C and C++ Even though object-oriented programming is central to C++, you still need to know basic structural constructs to do the job. The implementation of the member functions of a class (i.e. methods in OOP term) is largely structural programming. Almost all the structural programming constructs in C are also valid in C++.

3/22 Relational Operators... int n; cout << "Enter a number: "; cin >> n; cout << "n<10 is " << (n < 10) << endl; cout 10 is " 10) << endl; cout << "n==10 is " << (n == 10) << endl;... A Sample Run: Enter a number: 20 n<10 is 0 n>10 is 1 n==10 is 0

4/22 Relational Operators (cont.) Displaying the results of relational operations, or even the values of type bool variables, with cout << yields 0 or 1, not false and true. The relational operators in C++ include: >, =, <=. Any value other than 0 is considered true, only 0 is false.

5/22 Logical Operators  Logical AND Operator: && if ( x == 7 && y == 11 ) statement ; Logical OR Operator: || if ( x < 5 || x 15 ) statement ;  Logical NOT Operator: ! if !(x == 7) statement ;

6/22 Operator Precedence SUM = SUM + 5 OR SUM =+ 5

7/22 Conditional Statement: if Syntax

8/22 Conditional Statement: if…else Syntax If (x > 100) statement ; else statement ; A statement can be a single statement or a compound statement using { }.

9/22 Conditional Statement: switch Syntax switch(speed) { case 33: statement ; break; case 45: statement ; break; case 78: statement ; break; } Int a,b,c; char op; cin >> a >>op >>b; switch(op) case ‘+’: c= a+b;break; case ‘-’: c= a-b;break; default: cout <<“unknown operator”; }

10/22 Conditional Operator Syntax

11/22 Conditional Operator Syntax result = (alpha < 77) ? beta : gamma; is equivalent to if (alpha < 77) result = beta; else result = gamma;

12/22 Result = (num > 0)?‘positive’: (num<0) ?’negative’: ’zero’ is equivalent to if num>0 result = ‘positive’; else if num <0 result = ‘negative’; else result = ‘zero’; Example

13/22 The for Loop Syntax

14/22 The for Loop Control Flow

15/22 Example For (I=1;I<=10;I++) cout << I;cout << “*” cin>>n; For (I=1;I<=10;I++) For (I=1;I<=n;I++) cout << “*” <<endl; sum = sum +I; cout << sum; For (I=1;I<=3;I++) For (j=1;j<=10;j++) cout << I << “*” <<j<<“=“<<I*j;

16/22 The while Loop Syntax

17/22 The while Loop Control Flow

18/22 Example i = 1; While (i<=10) cout << i; Cin >> n; I = 1; While (I<=n) { sum = sum + I; cout << sum } While ( I<=10 ) cout << “*”;

19/22 The do Loop Syntax

20/22 The do Loop Control Flow

21/22 Example Do {cout <<I; I = I +1; } while (I<=10); Cin >> n; Do { cout <<I; I ++; } while (I<=n)

22/22 Functions Def : Set of statements used for a specific task Syntax: returntype fName( arguments) {… statements return variblename} Types of functions: 1. Function with no arguments and no return 2. Functions with argument and no return 3. Functions with argument and a return

23/22 Using Functions To Aid Modularity... void starline(); // function prototype int main() {... starline();... starline(); return 0; } void starline() // function definition { for(int j=0; j<45; j++) cout << '*'; cout << endl; }

24/22 Passing Arguments To Functions void repchar(char, int); int main() { char chin; int nin; cin >> chin; cin >> nin; repchar(chin, nin); return 0; } void repchar(char ch, int n) { for(int j=0; j < n; j++) cout << ch; cout << endl; }

25/22 Returning Values From Functions float lbstokg(float); int main() { float lbs; cout << "Enter your weight in pounds: "; cin >> lbs; cout << "Your weight in kg is " << lbstokg(lbs) << endl; return 0; } float lbstokg(float pounds) { return * pounds; }

26/22 Using Structures To Group Data struct part { // declare a structure int modelnumber; // ID# of widget int partnumber; // ID# of widget part float cost; // cost of part }; int main() { part part1; part1.modelnumber = 6244; part1.partnumber = 373; part1.cost = ; cout << "Model " << part1.modelnumber << ", part " << part1.partnumber << ", cost $" << part1.cost << endl; return 0; }

27/22 Structures Within Structures struct Distance { int feet; float inches; }; struct Room { Distance length; Distance width; }; int main() { Room dining={ {13, 6.5},{10, 0.0} }; float l = dining.length.feet + dining.length.inches/12; float w = dining.width.feet + dining.width.inches/12; cout << "Dining room area is " << l * w << " square feet" << endl; return 0; }