1. 1 Introduction to C++ Noppadon Kamolvilassatian Department of Computer Engineering Prince of Songkla University

2. 2 Contents n 1. Introduction n 2. C++ Single-Line Comments n 3. C++ Stream Input/Output n 4. Declarations in C++ n 5. Creating New Data Types in C++ n 6. Reference Parameters

3. 3 Contents (continued) n 7. Const Qualifier n 8. Default Arguments n 9. Function Overloading n 10. Dynamic Memory Allocation with New and Delete

4. 4 1. Introduction n C++ improves on many of C’s features. n C++ provides object-oriented programming (OOP). n C++ is a superset to C. n No ANSI standard exists yet (in 1994).

5. 5 2. C++ Single-Line Comments n In C, /* This is a single-line comment. */ n In C++, // This is a single-line comment.

6. 6 3. C++ Stream Input/Output n In C, printf(“Enter new tag: “); scanf(“%d”, &tag); printf(“The new tag is: %d\n”, tag); n In C++, cout > tag; cout << “The new tag is : “ << tag << ‘\n’;

7. 7 3.1 An Example // Simple stream input/output #include main() { cout << "Enter your age: "; int myAge; cin >> myAge; cout << "Enter your friend's age: "; int friendsAge; cin >> friendsAge;

8. 8 if (myAge > friendsAge) cout << "You are older.\n"; else if (myAge < friendsAge) cout << "You are younger.\n"; else cout << "You and your friend are the same age.\n"; return 0; }

9. 9 4. Declarations in C++ In C++, declarations can be placed anywhere (except in the condition of a while, do/while, for or if structure.) n An example cout << “Enter two integers: “; int x, y; cin >> x >> y; cout << “The sum of “ << x << “ and “ << y << “ is “ << x + y << ‘\n’;

10. 10 n Another example for (int i = 0; i <= 5; i++) cout << i << ‘\n’;

11. 11 5. Creating New Data Types in C++ struct Name { char first[10]; char last[10]; }; n In C, struct Name stdname; n In C++, Name stdname; The same is true for enum s and union s

12. 12 6. Reference Parameters n In C, all function calls are call by value. –Call be reference is simulated using pointers n Reference parameters allows function arguments to be changed without using return or pointers.

13. 13 6.1 Comparing Call by Value, Call by Reference with Pointers and Call by Reference with References #include int sqrByValue(int); void sqrByPointer(int *); void sqrByRef(int &); main() { int x = 2, y = 3, z = 4; cout << "x = " << x << " before sqrByVal\n" << "Value returned by sqrByVal: " << sqrByVal(x) << "\nx = " << x << " after sqrByVal\n\n";

14. 14 cout << "y = " << y << " before sqrByPointer\n"; sqrByPointer(&y); cout << "y = " << y << " after sqrByPointer\n\n"; cout << "z = " << z << " before sqrByRef\n"; sqrByRef(z); cout << "z = " << z << " after sqrByRef\n"; return 0; }

15. 15 int sqrByValue(int a) { return a *= a; // caller's argument not modified } void sqrByPointer(int *bPtr) { *bPtr *= *bPtr; // caller's argument modified } void sqrByRef(int &cRef) { cRef *= cRef; // caller's argument modified }

16. 16 Output $ g++ -Wall -o square square.cc $ square x = 2 before sqrByValue Value returned by sqrByValue: 4 x = 2 after sqrByValue y = 3 before sqrByPointer y = 9 after sqrByPointer z = 4 before sqrByRef z = 16 after sqrByRef

17. 17 7. The Const Qualifier n Used to declare “constant variables” (instead of #define) const float PI = 3.14156; n The const variables must be initialized when declared.

18. 18 8. Default Arguments n When a default argument is omitted in a function call, the default value of that argument is automatically passed in the call. n Default arguments must be the rightmost (trailing) arguments.

19. 19 8.1 An Example // Using default arguments #include // Calculate the volume of a box int boxVolume(int length = 1, int width = 1, int height = 1) { return length * width * height; }

20. 20 main() { cout << "The default box volume is: " << boxVolume() << "\n\nThe volume of a box with length 10,\n" << "width 1 and height 1 is: " << boxVolume(10) << "\n\nThe volume of a box with length 10,\n" << "width 5 and height 1 is: " << boxVolume(10, 5) << "\n\nThe volume of a box with length 10,\n" << "width 5 and height 2 is: " << boxVolume(10, 5, 2) << '\n'; return 0; }

21. 21 Output $ g++ -Wall -o volume volume.cc $ volume The default box volume is: 1 The volume of a box with length 10, width 1 and height 1 is: 10 The volume of a box with length 10, width 5 and height 1 is: 50 The volume of a box with length 10, width 5 and height 2 is: 100

22. 22 9. Function Overloading n In C++, several functions of the same name can be defined as long as these function name different sets of parameters (different types or different number of parameters).

23. 23 9.1 An Example // Using overloaded functions #include int square(int x) { return x * x; } double square(double y) { return y * y; } main() { cout << "The square of integer 7 is " << square(7) << "\nThe square of double 7.5 is " << square(7.5) << '\n'; return 0; }

24. 24 Output $ g++ -Wall -o overload overload.cc $ overload The square of integer 7 is 49 The square of double 7.5 is 56.25

25. 25 10. Dynamic Memory Allocation with New and Delete In ANSI C, dynamic memory allocation is performed with functions malloc and free. typeName *ptr; //typeName is any type, such as int, float, char etc. ptr = malloc(sizeof(typeName)); n In C++, we use the statement ptr = new typeName; If memory cannot be allocated by new, a null pointer is returned.

26. 26 n To free memory space, in C we use the statement free(ptr); n In C++, we use delete ptr;

27. 27 Using New and Delete with Arrays int *arrayPtr; arrayPtr = new int[100]; Creates array dynamically delete [] arrayPtr; Be sure to use brackets ([]) when deallocating arrays of objects.