Introduction to QBASIC programming and basics

Introduction to QBASIC Programming
Mahesh Sharma, B.Sc. (Hons) Computing
Copyright © 2017.
© mahesh

Agendas Today
 Introduction
 Program and Programming Tools
 Algorithm and Flowchart
 Concept of QBASIC Programming
 Structure of QBASIC
 Constants and Variables
 Arithmetic and Relational Expressions
 Logical Operators
 Keywords and Syntax
 Library Function in QBASIC
© mahesh

Introduction
 Computer system needs instructions to perform
different tasks.
 These instructions are called command. A collection
or set of commands composes a program.
 Computer program are written using programming
languages in order to solves specific problem.
 Some of the popular examples of programming
languages are: %
QBASIC, C, C++, Java, PHP, MySql, .NET etc.
© mahesh

Program and Programming Tools
 Program is the collection of commands in systematic
order to perform specific tasks
 Programming is a technique or art to develop the
program
 Programmer is a person who develops the program
using programming language
 Programmers use programming tools to develop a
program. Algorithm and Flowchart are most popular
programming tools and technique to write a program
© mahesh

Algorithm
Step by Step Description of Program in Systematic Order
Source: http://images.slideplayer.com/35/10459273/slides/slide_16.jpg © mahesh

Rules for Good Algorithm
Input : specified and required input values
Output : outcome values or solution of problem
Definite : must be defined clearly about what should be
done
Effective : must be able to perform each step exactly in
finite amount of time
Finite : finite number of steps
Correct : must be able to generate correct and desirable
output
Algorithm
© mahesh

Algorithm and Flowchart
Diagrammatic representation of a program using
standard symbols
© mahesh

Flowchart Symbols
The basic flowchart symbols
© mahesh

FlowchartTypes
System Flowchart
Represents the system and
its components
Sequence of instructions to
solve specific work
Explains the total flow of
data inside the system
Complex logical structure
diagram
Program Flowchart
 Represents program and
its components
 Sequence of instructions
to solve specific problem
 Explains the instructions
to solve the problem
 Relatively easier logical
structure diagram.
© mahesh

Advantages of Flowchart
© mahesh
 Easy method to Understand and Communicate
 Easier approach than Algorithm and Coding
 Applicable to all types of programming languages
 Represents all the components of program
like input, process, logic and output
 Serves as a guide to programmers

Disadvantages of Flowchart
© mahesh
 Cannot replace all types of logics used in computer
program
 Takes long time to represent all components of
computer Program
 Not applicable for complex and big types of
program or System

Program Logic or Structure
Program consists of different types of logic or structures
based on the solution to the identified problems.
3 types of Program Logic or Structures are:
i. Sequence : set of instructions which are executed
one after another in a steps
ii. Selection : set of instructions which are executed
conditionally based on conditions that are either
true or false
iii. Iteration : set of instructions which are executed
repeatedly and conditionally by loop conditions
© mahesh

Programming in QBASIC
QBASIC is the most popular high level programming
language. Developed by Microsoft Company, USA.
Q => Quick
B => Beginners
A => All Purpose
S => Symbolic
I => Instruction
C => Code
Consists of two basic files QBASIC.EXE and QBASIC.HLP
For editing, debugging and executing programs
© mahesh

Structure of QBASIC
© mahesh
Structure consists of some of the standard
programming elements. They are:
 Character Set
 Variable and Constants
 Arithmetic Expressions
 Relational or Logical Expressions
 Keywords and Syntax
 Library Functions
 Conclusion

Character Set in QBASIC
© mahesh
Character set in QBASIC consists following
standard elements:
 Alphabet : (a-z), (A – Z)
 Digits : 0, 1, 2, ……….., 9 and
 Special Characters : + - * / () . , : ; > < “ ! @ $
etc.

Variable and Constants
© mahesh
Variable and Constants are the memory location of the
programming data. However they both are different
based on value in computer memory space.
i. Constant : Quantity whose value does not change
during program execution
ii. Variable : Quantity whose value may change during
program execution
Types of Variable:
a. Numeric Constant/Variable
b. String Constant/ Variable

Arithmetic Expressions
© mahesh
Arithmetic Expressions are the five basic mathematical
expressions used in QBASIC. They are:
i. Exponentiation (^)
ii. Multiplication (*) and Division (/)
iii. Addition (+) and Subtraction (-)
Follows General BODMAS Rule
QBASIC follows the hierarchy according
to the mathematical algebraic rules and
regulations

Logical Expressions
© mahesh
Logical Expressions are the formed by using two or more
expressions to return value TRUE or FALSE: The common
logical operators are:
i) AND ii) OR iii) NOT
Conjunction Disjunction Logical Negation
The result for two expressions A and B using the common
logical operators:

Keywords and Syntax
© mahesh
Keywords in QBASIC are the special types of variables
that are not applicable to use in computer program. Also
called reserved words by QBASIC.
For example: INPUT, PRINT, CLS, GOTO, IF, FOR,
WHILE, END, ENDIF, LET, etc.
Syntax is the set of rules and regulations that must be
followed to construct the program in QBASIC programming.
Also called Grammar for writing command and statement in
developing computer program.

Library Function
© mahesh
 ‘Library’ stands for collection in general
 Library Functions in QBASIC is the set or collection
of useful programs and instructions.
 Used to simplify the task of programmers.
 QBASIC library is rich with mathematical functions
like square root, log of number, sine of angle, etc.
For example: SQR(), LOG(), SIN(), etc.

Introduction to QBASIC programming and basics

More Related Content

What's hot

Similar to Introduction to QBASIC programming and basics

More from Ashmita Tuition Center

Recently uploaded

In this document

Introduction to QBASIC programming and basics