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Object oriented programming 10 variables input and output
- 1. Object Oriented Programming: 10 Variables Input and Output Prof Neeraj Bhargava Vaibhav Khanna Department of Computer Science School of Engineering and Systems Sciences Maharshi Dayanand Saraswati University Ajmer
- 2. 2 Input • Data must be loaded into main memory before it can be manipulated • Storing data in memory is a two-step process: – Instruct computer to allocate memory – Include statements to put data into memory
- 3. 3 Allocating Memory with Constants and Variables • Named constant: memory location whose content can’t change during execution • The syntax to declare a named constant is: • In C++, const is a reserved word
- 4. 4 Allocating Memory with Constants and Variables (continued) • Variable: memory location whose content may change during execution • The syntax to declare a named constant is:
- 5. 5 Putting Data into Variables • Ways to place data into a variable: – Use C++’s assignment statement – Use input (read) statements
- 6. 6 Assignment Statement • The assignment statement takes the form: • Expression is evaluated and its value is assigned to the variable on the left side • In C++, = is called the assignment operator
- 8. 8 Saving and Using the Value of an Expression • To save the value of an expression: – Declare a variable of the appropriate data type – Assign the value of the expression to the variable that was declared • Use the assignment statement • Wherever the value of the expression is needed, use the variable holding the value
- 9. 9 Declaring & Initializing Variables • Variables can be initialized when declared: int first=13, second=10; char ch=' '; double x=12.6; • All variables must be initialized before they are used – But not necessarily during declaration
- 10. 10 Input (Read) Statement • cin is used with >> to gather input • The stream extraction operator is >> • For example, if miles is a double variable cin >> miles; – Causes computer to get a value of type double – Places it in the variable miles
- 11. 11 Input (Read) Statement (continued) • Using more than one variable in cin allows more than one value to be read at a time • For example, if feet and inches are variables of type int, a statement such as: cin >> feet >> inches; – Inputs two integers from the keyboard – Places them in variables feet and inches respectively
- 12. 12 Input (Read) Statement (continued)
- 13. 13 Variable Initialization • There are two ways to initialize a variable: int feet; – By using the assignment statement feet = 35; – By using a read statement cin >> feet;
- 14. 14 Increment & Decrement Operators • Increment operator: increment variable by 1 – Pre-increment: ++variable – Post-increment: variable++ • Decrement operator: decrement variable by 1 – Pre-decrement: --variable – Post-decrement: variable— • What is the difference between the following? x = 5; y = ++x; x = 5; y = x++;
- 15. 15 Output • The syntax of cout and << is: – Called an output statement • The stream insertion operator is << • Expression evaluated and its value is printed at the current cursor position on the screen
- 16. C++ Programming: From Problem Analysis to Program Design, Fourth Edition 16 Output (continued) • A manipulator is used to format the output – Example: endl causes insertion point to move to beginning of next line
- 17. 17 Output (continued) • The new line character is 'n' – May appear anywhere in the string cout << "Hello there."; cout << "My name is James."; • Output: Hello there.My name is James. cout << "Hello there.n"; cout << "My name is James."; • Output : Hello there. My name is James.
- 19. Assignment Discuss the Usage of Assignment Operator and Declaration and Initiation of Variables in C++ Explain the Input and Output management in C++