QBASIC: A Tool For Modern Programming

QBASIC:

A TOOL FOR MODERN

PROGRAMMINGBY REDEN R. PATACSIL AND GIFTY BELLE MANAOIS

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.

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.

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

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:

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:

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.

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:

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.

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.

IF & THEN Command

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

IF & THEN Command

EXPRESSION SIGNS You can also enter the following statements, instead of the

equal sign:

IF & THEN Command

EXPRESSION SIGNS We can also combine signs.

ELSE Command Using the ELSE command, you can have

the program perform a different action if the statement is false.

EXAMPLE:

The following program uses ELSE with the END IF command:

ELSE Command

ELSE IF CommandThe 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.

You can have multiple ELSEIF commands, along with ELSE.

ELSE IF Command

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.

THANK YOU!

REDEN R. PATACSIL

& GIFTY BELLE

MANAOIS