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Computer

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QBASIC• Introduction•Punctuation•Variable•Operators•Statements

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INTRODUCTIONOPENING

1. Click the program of QBASIC. Where it is located in your computer.

2. Then the following window will appear. Then press ESC key to open the following window.

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BASIC COMMANDS • PRINT Command: The command which display text

and numbers in the screen.

• CLS command: Helps to make clear the screen after a command is executed.

• REM command: It helps to add text or remark for the user that will not be executed.

• END command: It stops the execution of the

program.

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PUNCTUATION• We will learn about the following

punctuation:

Comma Semicolon Colon

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Comma(,)The comma causes the output to be displayed after leaving a gap of approximately 8-10 characters.Syntax: PRINT “text”, “text”

It will execute the following.

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Semicolon(;)The semicolon causes the output to be displayed after leaving no space.Syntax: PRINT “text”; “text”

Execution will be the following

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ColonThe Colon allows to write more than one statement on a single line.Syntax: PRINT “text”: Print “text”

It will Print the following

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VARIABLEWe will know about the basic rules to use Variables.

A variable can be big or small, it may contain letter or numbers but the first letter should be a letter.

A variable cannot contain spaces.A special character is allowed in QBASIC

which is underscore.

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OPERATORS • We will know about three types of

operators:

1. Arithmetic Operators2. Relational Operators3. Logical Operators

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Arithmetic OperatorsOperation Arithmetic

SymbolExamplea = 20b = 10

Output

Addition + PRINT a + b 30

Subtraction - PRINT a - b 10

Multiplication * PRINT a * b 200

Division / PRINT a/b 2

Parenthesis ( ) PRIN a + (b*2) 40

Raising to a power ᶺ PRINT a ᶺ 2 400

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Relational OperatorsOperation Relational

SymbolsExamplea = 20b = 10

Output (Will result in TRUE or FALSE)

Greater than > a > b TRUE

Greater than or equal to > = a > = b TRUE

Less than < a < b FALSE

Less than or equal to < = a < = b FALSE

Equal to = a = b FALSE

Not equal to < > a < > b TRUE

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Logical OperatorsOperation Relational

SymbolsExamplea = 20b = 10c = 50

Output (Will result in TRUE or FALSE)

AND (All the conditions must be true for the final result to be true)

AND a>b and a>cHere, cond1 (a>b) is true but cond2 (a>c) is false. So the final result is false.

False

OR (Any one or all the conditions should be true for the final result to be true)

OR a>b and a>cHere, since one condition i.e. cond1 (a>b) is true, so the final result is true.

True

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STATEMENT• We will know about 3 statements:

1. INPUT2. IF…THEN…ELSE3. GOTO

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INPUT Statement• When a value of a variable is required to be

accepted during the execution of the program, then the INPUT command is used.

• Syntax: INPUT Variable nameExample

The output is in next slide.

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• At first

• Next

• And then

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IF…THEN..ELSE• This statement is used when decision-making is

required in the program.Example, REM Displaying the largest numberLET A=10LET B=20IF A>B THEN PRINT A; “is the largest number” ELSE PRINT B; “is the largest number”

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GOTO Command• GOTO command is used to shift the control of

the program to the desired command. To specify where the control of the program should go, label name is specified along with the GOTO command.

• Example, Print “line #1”GOTO 10PRINT “this line is skipped”10:Output will be

Line #1

The label name is always followed by a colon

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That’s All