Variables are used to store and label data in programs. They come in different data types like integers, floating point numbers, strings, and Booleans. In C++, variables are stored in memory cells and have certain naming rules - names must start with a letter and can include numbers and underscores but not spaces. The document provides examples of simple programs using variables to calculate mathematical operations and find dates.

1. Variables & Data Types
Programming-I C++ Programing

2. What is a variable
 Variables are used to store information to be referenced and
manipulated in a computer program.
 They also provide a way of labeling data with a descriptive name, so
our programs can be understood more clearly by the reader and
ourselves.
 It is helpful to think of variables as containers that hold information.

3. Data Types
Data Type Represents Examples
integer whole numbers -5 , 0 , 123
floating point (real) fractional numbers -87.5 , 0.0 , 3.14159
string A sequence of characters "Hello world!"
Boolean logical true or false true , false

5. Variables in C++

6. Memory Cell location

7. Variables Naming Rules
• Variable name must start with a letter
• May contain letters, numbers and the underscore character
• Emaple – Salary, name3, first_name, LastName
• Bad Example – 3name, first name

8. Variables Naming Rules
• No real limit to the length of variable name but that are too short
are’nt meaningful and variables that are too long aren’t practical

9. Practice Programms
1. Program that calculates the square of a number
2. Program to find your Day of Birth given Date of Birth
3. Area of a rectangle
4. Area of a circle
5. Find the speed of a car in a given distance and time