This document provides an overview of the QBASIC programming language and its commands. It discusses QBASIC's interpreter-based execution model and use of line numbers. It also covers basic QBASIC concepts like constants, variables, and commands for printing, clearing screens, and running programs. The document then examines specific commands in more detail, such as PRINT, INPUT, IF/THEN, ELSE, and ELSEIF. It provides examples of how to use expressions, variables, and conditional logic in QBASIC programs.

1. QBASIC:
A TOOL FOR MODERN
PROGRAMMING
BY REDEN R. PATACSIL AND GIFTY BELLE MANAOIS

2. Beginner’s All Purpose Symbolic
Instruction Code (BASIC)
 is an interpreter which means it reads every line, translate it and lets the
computer execute it before reading another.
 Each instruction starts with a line number.
RULES IN USING QBASIC
 Statements to be made should be in proper sequence.
 Each statement should have one BASIC command which are called
keywords.
 QBASIC has standard rules which are called Syntax.

3. QBASIC Data
 CONSTANT- data whose values does not change or remains fixed.
 NUMERIC CONSTANT – numbers used for mathematical calculations.
 ALPHANUMERIC CONSTANT – number or alphabets in double quotes.
 VARIABLE – data whose values change depending on calculations
executed by the program.
 NUMERIC VARIABLE – variable that holds numeric constant.
 ALPHANUMERIC VARIABLE – number or alphabets in double quotes.

4.  CLS – used to clear the screen.
 PRINT – used to display the output on the screen.
 REM – stands for REMARK. It gives an explanation of the program thereby
making the program more understandable.
 LET – assigns a value to a variable in a program.
 END – it is usually given at the end of the program.
 INPUT – allows users to enter values for a variable while running a program.
 DELETE <LINE NO.> - delete a line number in a program
 RUN – used to execute the program and get the output on the screen.
 NEW – used to totally write a new program.
 SYSTEM – used to exit the QBASIC program.
QBASIC Commands

5. PRINT Command
 The PRINT command tells QBASIC to print something to the screen.
 With the PRINT command, we can print numbers and letters to the screen.
EXAMPLE:

6. PRINT Command
 If you pass an expression to the PRINT command, the value returned is printed.
EXAMPLE:
 If you enclose the expression with quotation marks, the expression becomes a string
and is not evaluated.
EXAMPLE:

7. PRINT Command
 To place World onto
the previous line, place
a semi-colon after Print
“Hello”.
 If you put a comma instead
of a semi-colon on the first
line, the program will insert
spaces between two words.

8. Variables
 A variable is a piece of data kept in the computer’s memory.
 A variable is assigned to a letter(s) in the following way:

9. INPUT Command
INPUT- allows the user to enter either a string or a number,
which is then stored in a variable.
 If semi-colon (;) is used, the output will display a question mark (?).
If a comma (,) is used, the output will display blank or nothing.

10. INPUT+PRINT Command
 The INPUT and the PRINT command can be used to
utilize the variable in the INPUT command in
computations in the PRINT command.

11. IF & THEN Command
 The IF and THEN commands are used to
compare an expression and then perform
some task based on that expression.

12. IF & THEN Command
EXPRESSION SIGNS
 You can also enter the following statements, instead of the
equal sign:

13. IF & THEN Command
EXPRESSION SIGNS
 We can also combine signs.

14. ELSE Command
 Using the ELSE command, you can have the
program perform a different action if the
statement is false.
EXAMPLE:

15. The following program uses ELSE with the END IF command:
ELSE Command

16. ELSE IF Command
The ELSE IF command allows you to perform a
secondary action if the first expression was false. Unlike ELSE,
this task is only performed if a specified statement is true.

17.  You can have multiple ELSEIF commands, along with ELSE.
ELSE IF Command

18. MULTIPLE EXPRESSIONS
 You can have more
than one expression in
IF… THEN by using either
the OR operator or the
AND operator.
 The OR operator only
requires one expression to
be true in order to print
“Yes” in the following
program:
 The AND operator requires
both expressions to be
true.

19. THANK YOU!
REDEN R. PATACSIL
&
GIFTY BELLE MANAOIS