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QBASIC

 QBASIC(Quick Beginners all Purpose Symbolic Instructions Code) is a programming language. It supports structured programming.  The older version of the QBASIC is BASIC  invented by Professor J. G. Kemeny and T. E. Kurtz of Dartmouth College, New Hampshire, U.S.A. as a language for the beginners and was implemented in 1964. Later Microsoft Inc has been releasing QBASIC programming language. New version of QBASIC contains new features. QBASIC has its own compiler. QBASIC is supplied as an additional programming environment in DOS diskettes as an interpreter.

Basics of QBASIC
The foundation of QBASIC programming is made with various elements. These elements are discussed in the coming sections.
Basic Data Types:  Different types of data are sued in QBASIC. These are listed as follows.
DATA Type
Declaration Symbol
Maximum
Minimum
String
$
32767 Chars
0 Chars
Integer
%
32767
-32768
Long Integer
&
2147483647
-21474836478
Single(7 digit) precision
!
3.402823E+38
1.401298E-45
Double(15 digit) precision
#
1.7976931
4.940656 D324
User – Defined Data Types
String
There are two kinds of strings used in QBASIC. They are:
(a)   Variable – length String
(b)   Fixed length string
(a)    Variable – length string : A variable – length sring is a sequence of up to 32767 characters. The codes for these characters range from 0 – 127 for regular ASCII (American Standard Code for Information Interchange) characters, and from 128 – 255 for the extended – ASCII characters.
(b)   Fixed Length string: A fixed – length string contains a declared number of characters, no more than 32767. Like variable – length strings, a fixed – length string contains characters with code ranging from 0 – 255.
String type of data are assigned from right to a variable on the left of equal to sign. the variable contains $ sign as suffix.
A$= "Happy Diwali"
here, A$ is a variable and happy diwali is a actual data.
Integer Long Integer
Integers are stored as 16 bit binary numbers (two bytes) ranging in value from -32768 to +23767. Long integers are stored as assigned 32 – bit binary numbers( four bytes) ranging in value from -2147483648 to +2147483647.
User Defined Data Typed
Basic lets you define new data types using the TYPE statement. A user – Define type is an aggregate type made up of elementary BASIC types. for example, The following type statement defines a type, SymTabEntry.
TYPE SymTabEntry
Identifier AS STRING *40
LineNumber AS LONG
Value AS LONG
END TYPE
Constants
Constants are predefined values that do not change during program execution. There are two types of constants. There are:
(a)    String Constant
(b)   Numeric Constant
(a). String Constant:  A string constant is a sequence of alphanumeric characters enclosed by double quotation marks. There alphanumeric characters can be any of the characters whose ASCII codes fall within the range 0 – 255 (except the double quote character(").
(b). Numeric constants : A
Variable
A variable is a name that refers to an object, i.e. a particular number, string or record. A record is a variable declared to be a user-defined type, Simple variables refer to a single number, string or record. Array variables refer to a group of objects, all of the same type.
A numeric variable, whether, simple or array, can be assigned only a numeric value either integer, long integer, single precision or double precision. A string variable can be assigned only a character- string value.  You  can assign one record variable to another only if both variables are the sage user defined type.
Example,
A constant value:
a=9.5
The value of another string or numeric value:
B$="Disk of operators"
A$=B$
Variable Name
A QBASIC variable name may contain up to 40 characters. The characters allowed in a variable name are letters, numbers, the period(.) and the type  - declaration characters(%, &, !, # and $). The first character in a variable name must be a letter. If a variable begins with FN, it is assumed to be called to DEF FN function.
Expressions and Operators
An expression can be a string or numeric constant, a variable, or a single value obtained by combining constants, variable and other expressions with operators.
Operators perform mathematical or logical operations on value. The operators provided by BASIC can be divided into five categories.
a)      Arithmetic Operator
b)      Relational Operator
c)      Logical Operator
d)      Functional operator
e)      String operator
a)      Arithmetic Operators:  Arithmetic operators perform calculations.
Examples,
+                :           Addition
-                 :           Subtraction
*                :           Multiplication
/                 :           Division
%               :           Percentage
b)      Relational Operator :  Relational operators compare strings and numeric values. Relational operators compare two values. The result of the comparison is either true or false.
These are given below:
Operator
Relation
Expression
=
Equality
x=y
<> 
Inequality
x<>y
Greater
x>y
Less
x<y
>=
Greater than Equal
x> = y
<=
Less than Equal
x < = y
c)      Logical Operator : Logical operators text complex conditions or manipulate individual bits. Logical operators performs texts on multiple relations, bit manipulations, or Boolean operations and returns a true or false values to be used in making a decision.
Example,
if D<=200 And F<5 then 40
While i>=10 or k<0
The six logical operators in BASIC, listed in order of precedence,
Operators
Meaning
NOT
Logical Complement
AND
Conjunction
OR
Disjunction (inclusive "or")
XOR
Exclusive "or"
EQV
Equivalence
IMP
Implication
d)      Functional Operators : - Functional operators supplement simpler operators. A function is used in an expression to call a predetermined operation to be performed on an operand. For example, SQR is a function used twice in the following assignment statement.
A=SQR(25)
e)      String Operator :- String operators combine and compare strings. A string expression consists of string constants, string variables, and other string expressin consists of string constants, string variables, and other strings expressions combined by string operators. There are two classes of string operations: concatenation and string function.
Example,
A$="FILE" :B$="NAME"
PRINT A$+B$
Output
FILENAME
Flowchart
 A flowchart is a diagram that represent the acts such as inputs, calculations and output that must be performed in proper order to solve the problem with the help of program. Flowchart helps us design logically correct solutions to a problem. We can keep on making improvements on the flowchart until all the aspects of the problem have been represented in the diagram.
Algorithm
An algorithm is a well-defined sequence of acts or procedures to perform the solution of problem in a finite number of steps. Hence, a flowchart is an excellent vehicle to represent an algorithm. Stepwise instructions to solve the problem as known as algorithm.
Control Statement
Statements that controls the program statements. There are two types of control statements.
  1. Decision Making
a). If…….. then ……..else …….statement
b). Select………. Case Statement
2. Loop Statements
a). For Loop
b). While Loop
c) Do Loop
e) Goto Loop (breaking statement)
a)      If …. then ……else statement
The if else statement used to express conditional expressions. If the given condition is true then it will execute the statements; otherwise it will execute the optional statements.
Syntax: 1
if (Conditional _ Expression) then
statement1
statement2
else
statement1
statement2
end if
Example,
if(x>y) then
print "X is greater"
else
print "Y is greater"
end if
Syntax2.
if(conditional _Expression)
statement1
statement2
elseif(conditional _expression)
statement1
statement2
elseif(conditional _ expression)
statement1
statement2
else
statement1
statement2
endif
Example,
cls
input "Enter your choice";ch
if(ch=1)
print "The day is Sunday"
elseif(ch=2)
print "The day is Monday"
elseif(ch=3)
print "The day is Tuesday"
elseif(ch=4)
print "The day is Wednesday"
elseif(ch=5)
print "The day is Thrusday"
elseif(ch=6)
print "The day is Friday"
elseif(ch=7)
print "The day is Saturday"
else
print "Please don't type more than 7 and less then 0"
end if
b)      Select Case statement
The select case is a special multi way decision maker that tests whether an expression matches one of the number of constant values, and braces accordingly. The syntax is given below:
Select case <expression>
case is =<exp>
statement1
case is =<exp>
statement1
end select
Example,
cls
input "Your choice";ch
select case ch
case is=1
print "Sunday"
case is=2
print "Monday"
case is = 3
print "Tuesday"
case is=4
print "Wednesday"
case is =5
print "Thursday"
case is =6
print "Friday"
case is=7
print "Saturday"
end select
c). For Loop
The for loop is most commonly used statement in QBASIC. This loop consists of three expressions. The first expression is used to initialize the index value, the second to check whether or not the loop is to be continued again and the third to change the index value for further iteration.
Syntax:
for expression _ 1 to expression _ 2 step value
statement1
statement2
next <expression>
Example,
CLS
for i=1 to 10 step 2
print i
next i
d). While Loop
The second type of loop , the while loop, is used when we are not certain that the loop will be executed. After checking whether the initial condition is true or false and finding it to be true, only then the while loop will enter  into the loop operations.
Syntax:
While conditional _ expression
statement 1
statement 2
wend
Example,
CLS
x=1
while x<20
print x
x=x+1
wend
e). Do Loop
It also loop statement.
Syntax:
do
statement1
statement2
loop while(condition)
Example,
CLS
x=1
do
print x
x=x+1
loop while(x<=20)
f). Goto Statement
The Goto statement is used to alter the program execution sequence by transferring control to some other part of the program. There are two types of goto statement.
Unconditional Goto : The unconditional goto statement is used just to transfer the control from one part of the program to the other part without checking any condition. Normally, a good programmer will not prefer to use the unconditional goto statement in his program as it may lead to a very complicated program like a never ending process.
Syntax:
Start:
statement1
statement2
goto start:
Conditional Goto
The conditional goto is used to transfer the control of execution from one part of the program to the other in certain conditional cases.
Syntax:
start:
statement1
statement2
statement2
if(conditional_ Expression) then
goto start;
else
end
Practical
1. Write a program to print radius of the circle.
DEF fna (a) = 3.14 * r * r
INPUT "value of radius"; r
PRINT "the area of circle"; fna(a)
END
2. Write a program to print the simple interest.
CLS
pv = 5000
r = 12
t = 2
si = (pv * r * t) / 100
PRINT si
END
3. Write a program to find qube value.
CLS
INPUT "first value"; a
INPUT "second value"; b
INPUT "third value"; c
x = (a + b + c) ^ 3
PRINT x
END
4. Write a menu driven program to display a menu by using case statement.
s:
PRINT "main manu"
PRINT "*********"
PRINT " 1. change ic to nc"
PRINT "2.area of the circle"
PRINT "3. greater number"
PRINT "4.to calculate the total salary"
PRINT "5. month of the year"
PRINT "6. student result sheet"
PRINT "7.exit"
                INPUT "enter your choice", ch
                SELECT CASE ch
                CASE IS = 1
                CLS
                INPUT "indian currency", ic
                nc = ic * 1.6
                PRINT "the nepali currency", nc
                GOTO s:
                CASE IS = 2
                CLS
                INPUT "radius of circle", r
                pi = 3.14
                ac = pi * r ^ 2
                PRINT "area of the circle", ac
                GOTO s:
                CASE IS = 3
                CLS
                INPUT "value of x", x
                INPUT "value of y", y
                IF (x > y) THEN
                PRINT "x is greater"
                ELSE
                PRINT "y is greater"
                END IF
                GOTO s:
                CASE IS = 4
                INPUT "basic salary", bs
                hra = bs * 5 / 100
                ma = bs * 4 / 100
                ta = bs * 2 / 100
                da = bs * 4 / 100
               ts = bs + ma + da + hra + ta
               PRINT "total salary", ts
               GOTO s:
               CASE IS = 5
               INPUT "value of the month", m
               SELECT CASE m
               CASE IS = 1
               PRINT "junary"
               CASE IS = 2
               PRINT "february"
               CASE IS = 3
               PRINT "march"
               CASE IS = 4
               PRINT "april"
               CASE IS = 5
               PRINT "may"
               CASE IS = 6
               PRINT "june"
               CASE IS = 7
               PRINT "july"
               CASE IS = 8
               PRINT "august"
               CASE IS = 9
               PRINT "september"
               CASE IS = 10
               PRINT "october"
               CASE IS = 11
               PRINT "november"
               CASE IS = 12
               PRINT "december"
               END SELECT
               GOTO s:
               CASE IS = 6
               INPUT "student result sheet", result
               INPUT "eng", eng
               INPUT "math", ma
               INPUT "nepali", ne
               INPUT "science", sc
               tot = eng + ma + ne + sc
               percent = tot / 4
               IF (percent >= 60) THEN
               PRINT "first"
               ELSEIF (percent >= 45) THEN
               PRINT "second"
               ELSE
               PRINT "third"
               END IF
               PRINT "total", tot
             
PRINT "percent", percent
               END
               CASE IS = 7
               END
               END SELECT
5. Write a program to print maximum value and minimum number. number input through the keyboard.
CLS
DIM x(10)
FOR i = 1 TO 10
INPUT " any value"; x(i)
NEXT i
max = x(1)
min = x(1)
FOR i = 1 TO 10
IF max < x(i) THEN max = x(i)
IF min > x(i) THEN min = x(i)
NEXT i
PRINT "the maximum value"; max
PRINT "the minimum value"; min
END
6. Write a program to print Fibonacci series.
CLS
x = 1
y = 1
PRINT x
WHILE z < 144
z = x + y
PRINT z
x = y
y = z
WEND
END
7. Write a program to enter  student marks from the keyboard and print the total mark, percentage, division and result.
CLS
INPUT "marks of english=", en
INPUT "marks of math=", ma
INPUT "marks of nepali=", ne
INPUT "marks of science=", sc
INPUT "marks of social=", soc
total = en + ma + ne + sc + soc
percent = total / 5
f$ = "first"
s$ = "second"
t$ = "third"
p$ = "pass"
f1$ = "fail"
CLS
PRINT "**********************************************************"
PRINT "marks of english=", en
PRINT "marks of math=", ma
PRINT "marks of nepali=", ne
PRINT "marks of science=", sc
PRINT "marks of social=", soc
PRINT "total marks= ", total
PRINT "percentage=", percent
IF (percent >= 60) THEN
PRINT "the division is:first"
ELSEIF (percent >= 45) THEN
PRINT "the division is:second"
ELSE
PRINT "the division is:third"
END IF
IF (en >= 32 AND ma >= 32 AND ne >= 32 AND sc >= 32 AND soc >= 32) THEN
PRINT "the result is:pass"
ELSE
PRINT "the result is:fail"
END IF
PRINT "******************************************************************"
END
Functions:
Functions are the ready made formula in QBASIC . There are mainly two types of functions in QBASIC.
1.      String Functions
For Example,
CHR$, ASC, STR$, UCASE$, LCASE$ DATE$, TIME$ Etc.
2.      Numeric Functions
For Example,
ABS, SIN, TAN, COS, Etc.
File Handling

Open

It is a command which opens a file to read and write in qbasic.
Syntax
Open <mode>, <file number>, <file Expression>
Example,
OPEN "O", #1,"hari.txt"

 

Mode in File handling

"O"  : - Write data into a sequencial file.
"I"  :-  Reads data form the sequencial file.
"A" :- Write data into a sequencial file from the end of the records. Or appends the records or data.
"R"      Reads or writes the files from the random access file.
"B"       :- Read or write data from binary file.

 

CLOSE

This command closes all open files which are opened to read and write data.
Syntax:
CLOSE <File number>
Example,
CLOSE #1

WRITE

This command allows you to write the data into sequecial a file.
Syntax:
Write <File Number>, Expression1, expression2..exp n.
Example,
WRITE #1,NAME$,ADDRESS$,PHONE
WIRTE #1, "HARI", "BARDIA", 524545

PRINT# 

The print# command allows you to store or write data into a sequencial file.
Syntax:
Print <Fine number> ,Expression1, Expression2....exp n.
Example,
PRINT #1,NAME$,ADDRESS$,PHONE

INPUT #

INPUT Command reads data form the sequencial file and assigns them into a variable.
Syntax:
INPUT <FILE Number>, <Exp1.exp2...expn.>
Example,
INPUT #1,NAME$,ADD$,PHONE

LINE INPUT #

The LINE INPUT# Command reads an entire line from the sequential file.
Syntax:
LINE INPUT <FILE Number>,Exp1, Exp2..expn.>
Example,
LINE INPUT #1, REC$

INPUT$

 It reads the strings or characters up to n from the sequential file.
Here n means number of charactes.
Syntax:
INPUT$(N,<File number>)
Example
INPUT$(12,#1)
EOF( ) :-End of File;
EOF() is a function which checks or tests the end of file condition. It will check that the file records are end or not.
Syntax:
EOF(File Number)
Example,
While EOF(#1)
Print "Name";name$
Print "Address";add$
Print "Phone";phone
Wend
KILL
It is command which deletes the files in DOS.
Syntax:
KILL <file Name>
Example,
Kill "hari.txt"
NAME AS
 It is a command which renames the file old name to new name in DOS.
Syntax:
NAME  <OLD FILE NAME> AS <NEW FILENAME>
EXAMPLE,
NAME "Hari.txt" as "Geeta.txt"
MKDIR
 It will create a new directory.
Syntax:
MKDIR <Directory Name>
Example,
MKDIR "Hari"
CHDIR
Change Directory To come to one step up of the existing directory.
Syntax
CHDIR <Existing Directory Name>
Example,
CHDIR "hari"
RMDIR :- Remove Directory
It can be use to remove the directory in dos .
Syntax:
RMDIR <existing directory name>
Example,
RMDIR "HARI"

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