Data Types & Variables

Transcription

1 Fundamentals of Programming Data Types & Variables Budditha Hettige

2 Exercise 3.1 Write a C++ program to display the following output.

3 Exercise 3.2 Write a C++ program to calculate and display total amount of the given unit price and quantity of an item.

4 Data types

5 Data Types Use various variables to store various information Variables are reserved memory locations to store values When you create a variable you reserve some space in memory Based on the data type of a variable, the operating system allocates memory and decides what can be stored in the reserved memory

6 C++ Data Types Seven basic C++ data types

7 Modifiers Several of the basic types can be modified using one or more of these type modifiers signed unsigned short long

8 Character types char They can represent a single character, such as 'A' or '$'. The most basic type is char, which is a one-byte character.

9 Numerical integer types int They can store a whole number value, such as 7 or 1024.

10 Floating-point types float They can represent real values, such as 3.14 or 0.01

11 Size of a data type Use sizeof() function to check the size

12 Answer Result which can vary from machine to machine/ Compilers

13 Data type selection

14 Memory Allocation

15 Define Variables in C++ Tell the compiler where and how much to create the storage for the variable Data Type <spase> Variable Name int number; char letter; float emp_salary

16 Variable name( rules) Can use only letters, digits and underscore The first character must be a letter or underscore Case sensitive Cannot use keywords No limits on length

17 C++ Variables Better not to begin a variable name with underscore. To form a name from two or more words, separate them with underscore Example int student_age; float employe_salary; char grade ;

18 Local & Global Variables data_size age

19 Variables in a program

20 Exercise 3.3 Write a C++ program to calculate and display total amount of the given unit price and quantity of an item.

21 Answer

22 Type Casting A way to convert a variable from one data type to another data type Use cast operator (type_name) expression (int) float_value

23 C++ Memory concept Variable names correspond to location in the computer s memory Every variable has a name, a type, a size and a value A memory cell is never empty. But its initial contents may be meaningless to your program. The current contents of a memory cell are destroyed whenever new information is placed in that cell.

24 Input / Output

25 Standard Streams cin is the standard input, normally the keyboard. To input data from keyboard use the word cin, followed by the Extraction operator (>>) cin >> x; Wait for a value to be entered at the keyboard and (when enter is pressed) will put that value into variable x.

26 Exercise 3.4 Write a C++ program to read two numbers from keyboard and display the total.

27 Answer

28 Exercise 3.5 Create a C++ program to calculate and display total amount of given unit price and quantity of the some item.

29 Answer

30 Output To output data onto the screen, use the word cout, followed by the insertion operator (<<).

31 Change the output Format Adjusting field widths Use the width() member function to set the field width to display a value. cout.width(10)

32 Example

33 Floating-point notation

34 Example

35 Floating-point Precision Sets the decimal precision to be used to format floating-point values on output operations. precision(number);

36 Example

37 Exercise 3.6 Write a C++ program to read price of the 3 items and print the total

38 Answer

39 Examples 1. Write a C++ program to read 3 integer numbers and find the total and average 2. Write a C++ program which will convert a weight in KG to pounds and ounces. ( 1 Kg = pounds)

40 Example Write a C++ program which will convert a Celsius temperature into Fahrenheit