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Array in C++ / review

Array in C++ / review

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Array in C++ / review

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  1. Array in C++ / review

  2. An array contains multiple objects of identical types stored sequentially in memory. • The individual objects in an array, referred to as array elements, can be addressed using a number, called index or subscript. • The array is the most commonly used data storage structure. • It helps us to see how object-oriented programming and data structures relate to each other.

  3. Like a regular variable, an array must be declared before it is used. A typical declaration for an array in C++ is: type name [ no of elements]; • You can create an array from any type with the exception of some special types. • An array always occupies a contiguous memory space. To know how much memory spaces an array needs, for example, if we have an array of 10 elements, this space is 10*sizeof(float) = 40 bytes.

  4. when declaring an array, there is a possibility to assign initial values to each one of its elements. • To access the values of an array; being able to both read and modify its value by using this format : • name[index]

  5. # include <iostream> # include <iomanip> using namespace std; int main() { int n[10]; for( int i=0;i<10;i++) n[i] =0; cout<<“Element”<<setw(13)<<“value”<<endl; for(int j=0; j<10;j++) cout<<setw(7)<<j<<setw(13)<<n[j]<<endl; return 0; }

  6. How to assign initial values to a char array : char name[ ] = “welcome back"; This definition is equivalent to char name[ ] = {‘w’, ‘e’, ‘l’, ‘c’, ‘o’, ‘m’, ‘e’, ‘ ‘ , ‘b’, ‘a’, ‘c’, ‘k’, ‘\0’};

  7. Multidimensional arrays • can be described as "arrays of arrays". • Multidimensional arrays are not limited to two indices. #define WIDTH 3 #define HEIGHT 2 int table [HEIGHT][WIDTH]; int n,m; int main () { for (n=0;n<HEIGHT; n++) for (m=0; m<WIDTH; m++) { table [n][m]=(n+1)*(m+1); } return 0; }

  8. Array Advantages: • Easier to declare and use. • Can be used with most of the data types. Array Disadvantages: • Fixed size data. • Ex: if the number of elements to be stored are more than the maximum size, the array cannot accommodate those new values.

  9. Any Question? • Refer to chapter 1 of the book for further reading

  10. Function Review

  11. FUNCTIONS • If you are looking to provide a solution for a more complex problem, it will help to divide the problem into smaller units. • Functions can be defined in any order, however, the first function is normally main. • Definition syntax: type name ( parameter1, parameter2, ...) { statements }

  12. Prototype and Definition • In a function definition, the function header is similar in form to the prototype(declaration) of a function. • State the differences between the prototype and function declaration? • When do the function must be declare? • The prototype provides the compiler with all the information it needs when a function is called, what are these information and what will happen after that? • Can the function declaration be omitted ? When ?

  13. ■ RETURN VALUE OF FUNCTIONS • When a function is called, an argument of the same type as the parameter must be passed to the function for each parameter. • Note: the arguments can be also any kind of expressions. • If the function is any type other than void, the return statement will cause the function to return a value to the function that called it. • When the program flow reaches a return statement or the end of a function code block, where it goes?

  14. ■ PASSING ARGUMENTS • Passing values to a function when the function is called is referred to as passing by value, does it access the object it self directly? • However, function arguments can also be passed by reference.

  15. Other topics to review • Overloading function . • Inline function . • Recursion . • Default arguments.

  16. Any Question? • Refer to chapter 1 of the book for further reading

  17. Pointers

  18. Each cell can be easily located in the memory because it has a unique address. Reference operator (&) • The address that locates a variable within memory is what we call a reference to that variable. • This reference can be obtained by preceding the identifier of a variable with an ampersand sign (&), known as reference operator. • Note that using the address/refrence operator, &, for a given object creates a pointer to that object. • Example: given that var is an int variable, &var is address of the object var

  19. Dereference operator (*) • A variable which stores a reference to another variable is called a pointer. • Using a pointer we can directly access the value stored in the variable which it points to. • To do that, precede the pointer's identifier with an asterisk (*), which acts as dereference operator and that can be translated to "value pointed by".

  20. Pointer variable - declaration and initialization • A pointer is an expression that represents both the address and type of another object. • Any pointer is placed during runtime in the specific memory address. • An expression such as &var is a constant pointer; however, C++ allows you to define pointer variables, that is, variables that can store the address of another object. • In a declaration, the star character * always means “pointer to.” • Example: int *ptr; • Pointer variables contain memory addresses as their values.

  21. After declaring a pointer variable, you must point the pointer at a memory address by using the address operator. • Example : int y = 5; // declare variable y int *yPtr; // declare pointer variable yPtr the statement yPtr = &y; // initialize-assign address of y to yPtr

  22. Example

  23. Indirection operator • The indirection operator(dereference operator) * is used to access an object referenced by a pointer: • Given a pointer, ptr, *ptr is the object referenced by ptr. • Example: long a = 10, b, *ptr; ptr = &a; // Let ptr point to a. b = *ptr; • Note : The indirection operator * has high precedence, just like the address operator &. Both operators are unary.

  24. References

  25. DEFINING REFERENCES • A reference is another name, or alias, for an object that already exists. • Defining a reference does not occupy additional memory. • Any operations defined for the reference are performed with the object to which it refers.

  26. The ampersand character, &, is used to define a reference. Given that T is a type, T& denotes a reference to T. • Example: float x = 10.7; float& rx = x; //The place contents the value 10.7. have two names and one address. cout<<x<< endl; //output: 10.7 cout<<&x<<endl; //address of x in memory cout<<rx<< endl; // output: 10.7 cout<<&rx<< endl; //address of x in memory = &x

  27. Any Question? • Refer to chapter 1 of the book for further reading

  28. Classes In C++

  29. What is a class • Can make a new type in C++ by declaring a class. • A class is an expanded concept of a data structure: instead of holding only data, it can hold both data and functions. • It is just a collection of variables with a set of related functions. • Thevariablesin the class are referred to as the member variables or data members. • The functions in the class manipulate the member variables. They are referred to as member functions or methods of the class.

  30. An object is an instantiation of a class. In terms of variables, a class would be the type, and an object would be the variable. • A class enables you to encapsulate these variables and functions into one collection, which is called an object. Declaring a Class • To declare a class, use the class keyword followed by a class name and an opening brace, then list the data members and methods of that class. • End the declaration with a closing brace and a semicolon.

  31. Example: class Part { intmodelnumber; double cost; voidSetPart(int mn, double c); void ShowPart(); }; • Note : • You cannot initialize data members where you declare them. • A method declaration can also include the implementation, or you can implement it separately). • All methods can be accessed only through an object of the class.

  32. Defining an object • An object is an individual instance of a class. • To define an object of a new type just as defining an integer variable (or any other variable): Part wheel; • This code defines wheel, which is an object whose class (or type) is Part.

  33. Calling Data Member and methods • Once you define an actual Part object, for example, wheel you use the dot operator (.) to access the members of that object. • Therefore, to assign 50 to wheel’s modelnumber member variable wheel.modelnumber = 50; • In the same way, to call the ShowPart() function, wheel.ShowPart(); //method calling

  34. Assign Values to Objects, Not to Classes • In C++ you don't assign values to types; you assign values to variables. • For example, int x = 50; //define x to be an int int = 50; // wrong • In the same way, Part.modelnumber = 50; //wrong • you must define a Part object and assign 50 to the modelnumber of that object. Part wheel; //just like int x; wheel.modelnumber = 50; //just like x = 50;

  35. Using Access Specifiers • C++ allows to control where the data members of a class can be accessed to protect them . • An access specifieris a word that controls where the data members in a class can be accessed. • An access specifier affects all members of the class that come after it until another access specifier is encountered or until you reach the end of the class. class ClassName { classMembers; accessSpecifier: classMembers; };

  36. A class has two kinds of access specifiers: public and private. • public members can be accessed anywhere that an object of the class can be accessed and from within the class (that is, in the class’s methods). • private members can be accessed only from within the class itself. • Note: an object of the class cannot access the private members, except through public methods. • If no access specifier is provided in the class, all members default to private.

  37. Example class Part { public: intmodelnumber; double cost; voidSetPart(int m, double c); void ShowPart(); }; • Now wheel.modelnumber = 50; compiles without problems.

  38. Private and Public Data • Usually the data within a class is private and the functions are public. However, there is no rule for that .

  39. Memory Allocation • Declaring this class doesn't allocate memory for a Part . • It just tells the compiler what a Part is, what data it contains, and what it can do. • It also tells the compiler how big a Part is (that is, how much room the compiler set for each Part (objects) that you create).

  40. Creating Methods • You can declare a method two ways. • The most common way is to declare a method inside the class declaration and then implement it outside. • The second way is to declare and implement the method at the same time inside the class declaration. • However, there is special syntax for the method definition. A member function definition begins with the return type, followed by the name of the class, two colons (::), the name of the function, and its parameters.

  41. The general syntax for a method implementation that occurs outside a class: return_typeClassName::methodName(parameterList) { method implementation; } • The double colon (::) is called the scope resolution operator.

  42. Constructor and Destructor • These are special kinds of methods that can be in a class, and they are optional • They provide special functionality that other methods cannot provide. • A constructor is executed every time you declare a new object. • It is normally used to set initial values for the data members. • always has the same name as the class and cannot have a return value (not even void).

  43. Adestructoris the opposite of a constructor and is executed when the object is destroyed. • It is always named the same name as the class, but with a tilde (~) at the beginning. • It cannot have arguments or a return value. • A destructor is often used to perform any necessary cleanup tasks.