QBASIC

Chapter 6: First Steps in Programming

What is a Program?

A program is a set of instructions given to a computer to perform a specific task.

These instructions are written in a language that the computer can understand and execute.

What is a Programming Language?

A programming language is a language used to write programs and communicate instructions to a computer.

Some common examples of programming languages include:

• C
• C++
• Java
• Python
• JavaScript

These languages help programmers create applications, websites, games, and software systems.

What is QBASIC?

QBASIC is a simple programming language used mainly for learning basic programming concepts.

Key Facts About QBASIC

• BASIC stands for Beginner’s All-purpose Symbolic Instruction Code.
• QBASIC was designed for beginners to learn programming easily.
• It was developed by:
  • Professor John G. Kemeny
  • Thomas E. Kurtz
• They developed BASIC at Dartmouth College, USA.
• BASIC was first introduced in the 1960s.
• QBASIC is commonly used to create small programs for learning purposes.

Elements of a Programming Language

Programming languages are made up of several basic elements.

Character Set

A character set is a group of symbols used to write programs.

It includes:

1. Digits

Numbers from:

0, 1, 2, 3, 4, 5, 6, 7, 8, 9

2. Letters

Alphabet letters from:

A to Z

a to z

3. Special Characters

Examples:

+   -   *   /   %  

<   >   =  

(   )   ;   :  

!   $   #   ?

Constants

A constant is a value that does not change during program execution.

Constants remain fixed throughout the execution of a program.

There are two types of constants:

1. Numeric Constants
2. String Constants

1. Numeric Constants

A numeric constant is a value on which mathematical operations can be performed.

Operations include:

• Addition
• Subtraction
• Multiplication
• Division

Features of Numeric Constants

• Consist of digits
• Can be positive or negative
• Used in calculations

Types of Numeric Constants

Integer Type

Whole numbers without decimal points.

Examples:

1

234

456

-50

Real Number Type

Numbers that include decimal points.

Examples:

7.8

0.765

-12.45

2. String Constants

A string constant is a value on which mathematical calculations cannot be performed.

It consists of letters, numbers, or special characters.

Features of String Constants

• Also called alphanumeric constants
• Always enclosed within double quotes (" ")
• Can contain letters, digits, or symbols
• In BASIC, strings can be up to 255 characters long

Examples:

"vikasmishra"

"vmsmprogramming"

"1234"

"Hello World"

Variables

A variable is a value that can change during program execution.

A variable represents a memory location in the computer where data is stored.

Each variable has:

• A name
• A value

The value of a variable can change while the program runs.

There are two types of variables:

1. Numeric Variables
2. String Variables

1. Numeric Variables

A numeric variable stores numeric values such as integers or decimal numbers.

Features of Numeric Variables

• Stores numbers
• Used in mathematical calculations
• Must follow naming rules

Example:

marks = 20

Where:

• marks → Variable name
• = → Assignment operator
• 20 → Numeric value

Rules for Naming Numeric Variables

• Must begin with a letter
• Cannot contain spaces
• Cannot contain special characters
• Can contain letters and numbers
• Length should be 1 to 8 characters (in QBASIC)

Example:

num1
total
value2

2. String Variables

A string variable stores text such as words or letters.

In QBASIC, string variables must end with a dollar ($) sign.

Example:

name$ = "vmsm"

Where:

• name$ → String variable
• "vmsm" → String value

Features of String Variables

• Store text or characters
• Used for names, addresses, messages
• Always contain values inside double quotes

Examples:

city$ = "Delhi"
message$ = "Welcome"