Saturday, 10 October 2015
IF…THEN…ELSE…END IF...ELSE IF COMMANDS IN QBASIC
The IF and THEN commands are used to compare an expression and then perform some task based on that expression.
Example:
x=5
if x=5 then print "Yes"
Output: Yes
Using the ELSE command, we can have the program perform a different action if the statement is false.
Example:
x=5
if x=5 then print "Yes" else print "No"
Output: Yes
END IF command allows us to have multiple commands after the IF…THEN statement, but they must start on the line after the IF statement. END IF should appear right after the list of commands.
Example 1: Example 2:
x=5 x=16
if (x=5) then if (x=5) then
input a$ input a$
print a$ print a$
end if else
end print x*2
end if
end
Output: 32
The ELSE IF command allows us to perform a secondary action if the first expression was false. Unlike ELSE, this task is only performed if specified statement is true.
Example 1:
x=6
If (x=6) then
Print “statement 1 is true”
Else if (x=6) then
Print “Statement 2 is true”
End if
Output: Statement 2 is true
Example 2:
x=8
If (x=5) then
Print “Statement 1 is true”
Else if (x=6) then
Print “Statement 2 is true”
Else
Print “No above statement is true”
End if
End
Output: No above statement is true
Multiple expressions: You can have more than one expression in IF … Then by using either the OR operator or the AND operator.
Example: x=5
If (x=5 or x=20) then print “Yes”
Output: Yes
Example: x=5
If (x>2 and x<6) then print “True”
Output: True
Example: x=16
Y=3
If ((x>5 and x<10) or y=3) then print “OK”
Output: OK
Example: x$=”Hello”
If (x$=”Hello” or x$=”Bye”) then print x$
Output: Hello
If the THEN part and the ELSE part, if any, can contain one or more IF-THEN-ELSE-END IF statement then it is a Nested IF-THEN-ELSE-END IFprogram.
Example:
IF (logical-expression) THEN
statements
IF (logical-expression) THEN
statements
ELSE
statements
END IF
statements
ELSE
statements
IF (logical-expression) THEN
statements
END IF
statements
END IF
PROGRAMS:
Q. Write a program to display the greater number between two numbers.
CLS
Input “First number=”; a
Input “Second number=”;b
IF a > b THEN
PRINT a; “ Is Greater Than ” ;b
ELSE
PRINT b;“ Is Greater Than ”; a
END IF
End
Q. Write a program to calculate that the numbers are same or not. If not display the greater number between the two numbers.
CLS
Input "Enter First Number: ", Num1
Input "Enter Second Number: ", Num2
If Num1 > Num2 THEN
Print Num1; "Is Greater Than"; Num2
Elseif Num2 > Num1 THEN
Print Num2; " Is Greater Than"; Num1
Else
Print “The Numbers Are The Same”
End if
End
Q. Write a program to enter any number and check that it is less than or greater than or equal to 100.
Cls
Input "Enter a number: ", Number
If Number < 100 then
Print "Your number was less than 100"
Else
Print "Your number was greater than or equal to 100"
End if
End
Q. Write a program to enter any number and find out whether it is negative or positive.
Cls
Input “Enter the number”; N
If N>0 Then
Print “ The number is positive”
Else
Print “The number is negative”
end if
End
Q. Write a program to print first 20 natural numbers using label.
Let count = 1
More:
Print count
Let count = count + 1
If count < 21 then goto More
End
Note: Line 2 is a label in our little program. A label is a single word that is not a QBASIC command (we call those reserved words because they are reserved for a special purpose) followed immediately by a colon. A label is a way to tell the computer where things are. We use a label to tell the computer where we will want to find something later on. In line 5, we look for that label, so that the computer program can jump to the next line (line 3) in the program and continue on from there. The word LET is actually optional!
Q. Write a program to compute the Summation (S) of values from 1 to 100 where:
S = 1+2+3+…………100.
Cls
S = 0
I = 1
More:
S = s + i
I = i + 1
Print s
If i <= 100 then goto More
End
Q. Write a program to compute the summation for even numbers from 0 to N.
Cls
S = 0
I = 0
Input “limit=”; n
More:
S = s + i
I = i + 2
Print s
If i <= n then goto More
End
Q. Write a program to compute Summation of X values from list of 10 different numbers.
Cls
S = 0
I = 10
More:
Input "value="; x
S = s + x
I = i - 1
If i >= 1 then goto More
Print s
End
Q. Write a program to input any number then determine if the number is odd or even.
Cls
More:
Input “number=”; n
If n<0 p then print”Number is integer” else print “Number is not an integer”
Input” Want to continue”; a$
If a$=”y” or a$=”Y” goto More
End
OR
Input X
If X= int(X) then print "x is integer" If X<> int(X) then Print "x is not integer"
Q. Write a program to calculate and print even numbers between 10 and 99.
Cls
I= 10
More:
Print i
I=i+2
If i<=99 then goto More
end
Q. Write a program to determine a student’s final grade and indicate whether it is passing or failing. The final grade is calculated as the average of four marks.
CLS
INPUT "The marks of Maths, Computer, History, English: "; M, C, H, E
Grade = (M + C + H + E) / 4
IF (Grade >= 40) THEN
PRINT "Pass"
ELSE
PRINT "Fail"
END IF
END
Q. Create a calculator on QBasic.
CLS
PRINT "Welcome to the QBasic Calculator!"
INPUT "Enter two numbers."; nm1, nm2
PRINT "Choose a basic operation:"
PRINT "1. Add 2. Subtract 3. Multiply 4. Divide "
INPUT operation
IF operation = 1 THEN PRINT "The result is"; nm1 + nm2
IF operation = 2 THEN PRINT "The result is"; nm1 - nm2
IF operation = 3 THEN PRINT "The result is"; nm1 * nm2
IF operation = 4 THEN PRINT "The result is"; nm1 / nm2
END
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