QBASIC Statements

QBASIC Statements

 

Introduction

A statement is a set of instructions written using keywords or commands of QBasic. Every programming language used keywords as a statement with certain rule (syntax). The keywords have specific meaning to the QBASIC programming. There are different types of QBASIC statements.  They are as follows

a) Assignment statement

b) Declaration statement

c) Input/output statement

d) Control flow statement

 

a. Assignment statement

The statement which is used to assign the value to the variable is known as assignment statement. LET, SWAP and READ…DATA are the commonly used assignment statements.

LET Statement

It is an assignment statement. The value can be assign in the variable with the help of LET statement.  LET is an optional statement.

Syntax: LET <variable> = <expression>

Where,

Variable : is the name of the numeric or string variable.

Expression : is the numeric or string value that the variable will hold

 Also Read:  Array in QBASIC

Example 1: Program to calculate the simple interest	Example 2: Program to display the name, address and age of the student
CLS REM program to calculate and display the simple interest LET p=10000 LET t=5 LET r- si=(p*t*r)/100 PRINT “Simple interest”;si END	CLS LET a$=”Ajaya Sharma” LET b$=”Dhangadhi” LET c=20 PRINT “Name”,”Address”,”Age” PRINT a$,b$,c END

 

SWAP Statement

The SWAP statement is used to interchange the values between two different variables of same type.

Syntax:  SWAP <variable 1> , <variable 2>

 

CLS REM this is the test of SWAP statement LET x= 20 LET y= 30 PRINT “It is Before Swapping” PRINT x,y SWAP x,y PRINT “It is After swapping” PRINT x,y END

Output:   It is Before swapping 20                    30 It is After Swapping 30                    20

Here variable a and b will change their value to each other.

 

READ…..DATA Statement:

READ: Read the values (numeric or string) and assigns them to variables.

DATA: It specifics values to be read by subsequent READ statement.

Syntax:

READ variable list

…………………….

…………………….

DATA constant list

Example:

REM this is the test of READ……DATA statement

READ n$, a$, a

PRINT “Name=”;n$

PRINT “Address”;a$

PRINT “Age”;a

DATA Ram, Dhangadhi, 16

 

 Restore Keyword

Restore keyword is used in READ…DATA statement. RESTORE keyword allows data for the reused. Once a DATA element has been read, it cannot be read again until either the program restarts or the RESTORE statement is used.

 

Syntax: RESTORE [line number/label]

 

CLS REM Program to test the RESTORE statement DATA 5,10 READ a,b RESTORE READ c,d PRINT a,b,c,d

Output: 5          10          5          10

 

b. Declaration statement

The statements which are used to declare the variables or constants are known as declaration statements. DIM, CONST and REM are the declaration statements.

DIM Statement

In the type of explicit variable declaration DIM statement is used.

DIM declares simple variable as well as array variable with their data type.

Syntax:    

DIM  variable [subscripts] [AS type]

 

DIM  variable1[subscripts] [AS type], variable2[subscripts] [AS type]

 

Example: 

DIM age AS integer

                 

DIM name AS string, age AS integer

 

CLS

REM sample of DIM statement

DIM n AS STRING

DIM a AS INTEGER

CLS

INPUT “Enter your name”;n

INPUT “Enter your age”;a

CLS

PRINT “Name”;n

PRINT “Age”;a

END

 

 CONST Statement

CONST declares symbolic constants to use in place if numeric or string values.

Syntax:              CONST constant name = expression

Example:

CLS

REM sample of CONST statement

INPUT “Enter radius”;r

CONST pi=3.146

A=pi*r^2

PRINT “Area”;a

END

 

REM Statement

It is a BASIC declaration statement that allows explanatory remarks to be inserted in a program. It does not execute in the program. It is also called non-executable statement. The alternative of REM is (‘)

Syntax:   REM <remarks>

Or,            ‘<remarks>

 

Example

 CLS
PRINT  "Some text"
‘ This text is ignored.

 

c.  Input / Output statement

Input/Output statements are used to get user input and display the processed result to the outside world (users). CLS, INPUT, LINE INPUT, PRINT, PRINT USING, LPRINT, LPRINT USING are the input / output statements.

 

CLS Statement

The CLS statement clears the screen. If you write CLS statement on the middle of the program than you cannot see that part because it clears the screen.

Syntax:     CLS

 

INPUT Statement

INPUT statement inputs or accepts data from the keyboard entry and stores to list of variables during the time of program execution. Variables separated by comma “,”.  INPUT statement brings question mark “?” on the screen. INPUT statement causes the program to pause and wait for data. Unless any response is entered the control does not move the next line.

Syntax:   INPUT [“prompt string”] [;|,] variable list

 

Prompt string is used to display on the screen to tell the user of the program what to enter at the keyboard.

Variable list is one or more variables used in the program are separated by comma.

Example:

CLS

INPUT “First Number:”;A

INPUT “Second Number:”;B

Sum=A+B

PRINT “The Sum is:”;Sum

END

 

LINE INPUT

This statement is used to read an entire line of input from the keyboard and store it in one string variable. It inputs data ignoring delimiters.

Syntax:   LINE INPUT [“prompt string”] ; string variable

When the INPUT statement is used to input multiple values from the user, commas must be used to delimit the input. If there are two variables being requested by INPUT, a comma must separate the two values, otherwise an input error occurs. If a comma is used when there is only one variable being inputted, there will be an error as well. With LINE INPUT, only one variable may be inputted, but commas do not cause errors when used. The fact that LINE INPUT will accept commas as part of the text string is the only difference between LINE INPUT AND INPUT.

  Syntax:

LINE INPUT "Type a sentence:"; sentence$

 Example:

CLS

LINE INPUT “What is your Name?”;N$

PRINT N$

END

 

INPUT #

This statement is used to retrieve data items from a sequential data file and store them into a list of variables.

Syntax:

 INPUT # [file serial number, variable 1, variable 2, …]

 

LINE INPUT #

This statement is used to retrieve an entire record from a sequential file and store it into one string variable.

Syntax:       

LINE INPUT # [file serial number, string variable]

 

INKEY$

It is an I/O function returns a one or two byte string containing a character read from the keyboard. A null string is returned if no character is waiting there. A one character string contains the actual character read from keyboard that reads a character from the keyboard.

 

Example:

PRINT “Press any key …”

DO

LOOP WHILE INKEY$ = “ ”

Note: This example pauses until the user presses a key.

 

PRINT Statement

PRINT statement provides output on the screen. An alternative of PRINT statement is question mark (?)

Syntax:       

PRINT [expression list] [ , | ; ]

 

Or,               

? [expression list] [ , | ; ]

Where.

Expression list: It is the list of one or more numeric or string expression.

Comma (,) is used to produce output on the same line after some space.

Semicolon(;) specify the next output to be displayed on the same line after a space immediately.

  

Example:	Output:
CLS REM test of PRINT statement PRINT “Wel-come to QBASIC” PRINT PRINT “====================” PRINT “AVN, Dhagadhi” LET a$=”RAM” LET b$=”KTM” ? a$, b$ END	Wel-come to QBASIC   AVN, Dhangadhi RAM                   KTM

 

PRINT USING Statement

This statement is used to print strings or numbers using a specified format to the screen.

Syntax::            

PRINT USING “format string” ; expression

 

Example:          

PRINT USING “####.##” ; 123

PRINT USING”##.#” ; 12.275

 

Output:             

123.00

                 12.2

 

Formatting character for numeric data

Character	Result
#	Digit position
+	Position of number’s sign
.	Decimal point position
-	Prints trailing minus sign for negative numbers only
**	Fills leading spaces with *
$$	Prints leading $
**$	Combines ** and $
^^^^	Prints number in exponential format

 

Formatting character for string data

Character	Result
&	Prints entire string
!	Prints only the first character
\  \	Prints first ‘n’ characters, where n is the number of blanks between slashes + 2

 

LPRINT and LPRINT USING Statements:

These statements function in the same way as the PRINT and PRINT USING statements except that output goes to the line printer and file number option is not permitted. . LPRINT will accept the same parameters that PRINT will, such as variables (numbers and string expressions), static text, and multiple combinations of each.

Also Read:

 Global variable in QBASIC for class 10 and SEE - Computer for SEE and NEB (neb-see-solution.blogspot.com)

Display the difference of input two numbers

C program to calculate the sum of n integer numbers using function.

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