This document discusses various programming concepts in QBASIC including control statements, loops, arrays, and library functions. Control statements like IF-THEN, IF-THEN-ELSE, and IF-THEN-ELSEIF are used to control program flow based on conditions. Common loops in QBASIC include FOR-NEXT loops, DO WHILE loops, and WHILE-WEND loops. Arrays allow storing and accessing multiple values of the same type. One-dimensional and two-dimensional arrays are covered. Finally, common library functions LEFT$, RIGHT$, and MID$ are introduced for extracting portions of string values.

1. VII CLASS
CHAPTER---->2
2. QBASIC
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2. CONTENTS
1) CONTROL STATEMENTS
2) LOOPS IN QBASIC
3) ARRAYS
4) LIBRARY FUNCTIONS
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3. 1) CONTROL STATEMENTS
• THESE STATEMENTS ARE USED TO
CONTROL THE PROGRAM.
• THE VARIOUS CONTROL STATEMENTS
ARE :
IF….THEN
IF….THEN…ELSE
IF….THEN…ELSEIF
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4. IF….THEN
• IT IS USED TO CHECK THE CONDITION &
EXECUTE THE STATEMENTS.
• SYNTAX :
IF <CONDITION>
THEN
< SET OF STATEMENTS>
• EXAMPLE:
IF CLASS =7 THEN PRINT “SRI CHAITANYA”
IF CLASS <>7 THEN PRINT “ U R NOT 7TH CLASS”
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5. IF…THEN….ELSE
IT IS USED TO CHECK THE CONDITION & EXECUTE THE STATEMENTS,
IF COND FAILS ELSE PART STATEMENTS WLL BE EXECUTES
• SYNTAX :
IF <CONDITION>
THEN
<STATEMENTS>
ELSE
<STATEMENTS>
• EXAMPLE :::
• ELIGIBLE TO VOTE OR NOT
IF AGE>=18
THEN
PRINT “ U R ELIGIBLE “
ELSE
PRINT “U R ! ELIGIBLE
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6. IF….THEN…ELSEIF
IT IS USED WHEN THERE IS MORE NO. OF CONDITIONS TO CHECK.
• SYNTAX :::
IF <CONDITION>
THEN
<STATEMENTS>
ELSEIF
<STATEMENTS>
ELSE
<STATEMENTS>
END IF
• EXAMPLE :::
• TO CHECK GREATEST
NUMBER
IF NUM1 > NUM2 THEN
PRINT NUM1 IS > NUM2
ELSEIF NUM2 > NUM1 THEN
PRINT NUM2 IS > NUM1
ELSE
PRINT “ BOTH NUMBERS ARE
EQUAL”
END IF
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7. LOOPS IN QBASIC
•WHAT IS LOOP ?
•THE STATEMENTS WHICH ARE REPEATEDLY
EXECUTED ARE CALLED AS LOOPS.
•LOOPS ARE OF MAINLY 3 TYPES :
A) FOR…Next
B)DO While…Loop
C)While…Wend
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8. A)FOR…Next
THIS LOOP IS USED TO EXECUTE THE STATEMENTS WHICH ARE
REPEATED.
SYNTAX
For COUNTER= START TO END
STATEMENTS
NEXT COUNTER
HERE,
COUNTER----> VARIABLE NAME
START -----> INITIAL VALUE
END -----> FINAL VALUE
EXAMPLE
For a=20 to 10 step -1
Print a;
Next a;
End
O/P:::
20 19 18 17 16 15 14 13 12 11 10
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9. B)DO While…Loop
THIS LOOP IS USED TO EXECUTE THE STATEMENTS UNTILL
THE CONDITION IS TRUE.
SYNTAX
DO WHILE CONDITION
STATEMENTS
LOOP
EXAMPLE
• PRINT “ WELCOME TO SCTS ”.
Let a = 1
Do while a < = 5
Print “WELCOME TO SCTS”
A = a + 1
Loop
End
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10. c) While…Wend
THE STATEMENTS INSIDE OF THIS LOOP EXECUTES
UNTILL THE CONDITION IS FALSE.
SYNTAX
While condition
STATEMENTS
WEND
EXAMPLE
• DISPLAY SQUARE
NUMBERS FROM 1 TO 4.
X=1
While x < 5
Print x; ‘’ SQUARE ” X * X
X = X + 1
Wend
End
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11. ARRAYS
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WHAT IS AN ARRAY???
ANS)
AN ARRAY IS A LIST OF VARIABLES WHICH IS
OF SAME DATATYPE.
ARRAY
TWO DONE D

12. • THE ARRAY WHICH IS USED TO STORE DATA IN A
LINEAR FORM IS CALLED ONE D ARRAY.
• THE ARRAY WHICH IS USED TO STORE DATA IN A
TABULAR FORM IS CALLED TWO D ARRAY.
SYNTAX
DIM ARRAYNAME(SIZE) AS DATATYPE
WHERE,
DIM----> VARIABLE
SIZE----> TELL US THE TOTAL NO.OF ELEMENTS
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13. WHAT IS STRING ARRAY
THE COLLECTION OF CHARACTERS IS CALLED AS STRING.
ARRAY EXAMPLE:
Dim Num(2) AS Integer
Dim Sum AS Integer
Num(1) = 10
Num(2) = 20
Sum = Num(1) + Num(2)
Print Sum
O/P :
30
• STRING ARRAY EX:
Dim sname(5) as string
Sname(1) = “ SRI ”
Sname(2) = “ CHAITANYA”
Sname(3) = “ SCHOOL ”
Print Sname(3)
End
O/P:
SCHOOL
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14. LIBRARY FUNCTIONS
• THESE FUNCTIONS ARE USED IN A PROGRAM
TO PERFORM THE PREDEFINED TASKS.
• THERE ARE MAINLY 3 FUNCTIONS AVAILABLE IN
LIBRARY FUNCTIONS. THEY ARE:::
A)LEFT$
B)RIGHT$
C)MID$
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15. LEFT$
IT IS USED TO EXTRACT
LEFTSIDE
CHARACTERS.
EXAMPLE
Machine$=“computer”
Print Left$(machine$,3)
O/P:
COM
RIGHT$
IT IS USED TO EXTRACT
THE RIGHT SIDE
CHARACTERS.
EXAMPLE
Machine$=“computer”
Print
Right$(machine$,3)
O/P :
TER
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16. MID$
• THIS FUNCTION IS MAINLY USED TO
EXTRACT SOME PORTION OF THE
STRING.
EXAMPLE :
machine$ = “computer”
Print mid$(machine$, 3,4)
O/P :
HERE,
3------> STARTING POINT OF EXTRACTION
4------> NUMBER OF CHARACTERS TO BE EXTRACT.
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MPUT

17. THANK U ALL
UR’S
VALI.. SIR
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