BASIC Programmiang
BASIC is an easy and simple high level programming language.
It was developed in 1964 t Dartmouth college by Professors John G. Kemeny and
Thomas E. Kurtz. Because of its simplicity and conversational nature, BASIC
quickly became one of the most popular programming language.
10.1 BASIC Programming
BASIC is the first high level language to be used on micro
computers. First interpreter of BASIC language was written in 1975 by
Microsoft. Most popular versions are GW BASIC and QBASIC.
BAIC has the following features:
Ø
It is easy language
Ø
It is a general purpose language, suitable for
scientific and commercial programming.
Ø
It has simple syntax rules and easy to test and
debug.
Ø
It is well suited for computers having limited
memory.
10.2 character set in BASIC
Character set in BASIC consists of the followings:-
Ø
The Alphabetic Characters In BASIC are capital
letter A, B, C………, Z and a, b, c, ……….z.
Ø
The numeric characters are digits 0, 1,2,……9.
Ø
Special characters such as $, #, %, @, \ blank
spaces and punctuations etc.
Ø
Arithmetic and relational operators such as +,
-, *, /, ^, (, ), =, >, < etc.
10.3 reserved words
Reserved words have special meaning in BASIC. They cannot be
used as variables. There are 160 reserved words in BASIC.
10.4 types of entries in BASIC
There are 3 types of entries in BASIC, which are commands,
program statements, and data.
Commands are executable instructions such as save, list etc.
some BASIC commands are described below:-
Auto
It generates an automatic line number each time
<enter> key is pressed.
Auto 80, 20 first number specifies the beginning of
the line number and second number specifies the increment in the line number.
Auto , 20 if
the number is not specified before comma then the first line number assumes 0.
Auto ., if
period is entered before comma, it indicates the current line, if the increment
is not specified then the last increment specified is assumed.
Clear
It clears value assigned to numeric and string variable.
Resuming all numeric variables to zero, all string variables to null and close
all open files.
Cls / home Executing
Cls or Home clears the screen and the cursor returns on the top left corner.
Delete
It deletes program lines or line range.
Delete 50 it
deletes the specified line.
Delete 30-50 it
deletes all the lines within range.
Delete -100 it
deletes all lines up to the end line number specified.
Delete 70- it deletes all lines from the line
number specified up to the end of the program.
Edit
It edits a specified line number
Edit 50 it
displays specified line to be edited.
Files
To display names of all files from the specified drive.
Files displays
all the filenames in the current directory.
Files “BAS” displays
all files having BAS extension.
Files “A” displays
all files on A drive.
Kill
To delete a file from disk.
Kill <filename> it
deletes the specified file.
List
To display the program or part of the program currently in memory.
List 20-50 lists
all programs between line numbers specified.
List 40- lists
all programs from line number specified.
List -50 lists
all programs up to the end line number specified.
Load
To load a file from diskette to memory.
Load “filename” it loads the specified file into memory.
New
To delete the currently in memory and clears all variables.
New it
erases the old program from memory and clears the screen.
Renum
To renumber program lines without changing lines order.
Renum 50, 35,
10 the first number specifies
new number for the first line, the second number specifies old number of the
line and the third number specifies increment.
Run
It begins
program execution currently in memory.
Run 40 if the number is specified
then execution begins from that line.
Save
It is used to
save a program file o a drive.
Save “A:try” it saves the try file on the disk in
drive A.
System
It is used to
exit BASIC.
10.5 Statements
Statements are part of computer program. They have specific
purposes in a program. Commands usually perform some type of program
maintenance such as editing running or saving programs. On the other hand
statements are part of programs and run in compiler mode.
A program in BASIC has two parts; a line number and one or
more instructions. For example
10 let A=10
10.6 Data type
BASIC has two data types.
Numeric Data
BASIC deals with data having numbers that are used in
calculations. For example 25 and 30.67 etc.
String Data
BASIC also deals with texts called strings. A string
consists of all the characters, word or numbers enclosed by quotation marks
such as “BRC Turbat”.
Constants
A constant in BASIC is something whose value does not change
during execution of program.
Variables
Variables are names used to represent certain quantities in
a BASIC program. Variable values can change during execution. There are two
types of variables, which are:-
a)
Numeric variables
A numeric variable has a numeric
value either supplied by the user or calculated by the computer during
execution. A numeric variable name may consist of all alphabets and numeric
constants but must begin with an alphabet such as Age.
b)
String variables
A string variable represents a
string that is a sequence of characters i.e letters, numbers and special
characters such as +,-,*, $, =,? Etc. a string name must be followed by a
dollar sign such as A$.
10.7 operators
Operators perform mathematical or logical operations on
values. In BASIC the operators are divided into four categories.
a)
Arithmetic operators
Numeric expression contains
operators that perform arithmetic operations called arithmetic operators.
Arithmetic
operators used in BASIC
Operation
|
operator
|
Addition
|
+
|
Subtraction
|
-
|
Multiplication
|
*
|
Division
|
/
|
Exponentiation
|
^
|
Negation
|
-
|
10.8 The hierarchy of arithmetic operators
The order in which various
operations are performed is as follows:-
First: perform all operation inside parenthesis.
Second: evaluate all exponentiation from right to left.
Third: perform all multiplication and divisions from left to
right.
Fourth: perform all additions and subtractions from left to right.
b)
Relational operators
Relational operators are used to
compare two quantities. The result of comparison may be either yes or no or
true or false, which decide the flow of the program.
Relational
operators
Operators
|
relation
|
=
|
equal
|
<>
|
Not equal
|
>
|
Greater than
|
<
|
Less than
|
>=
|
Greater than or equal to
|
<=
|
Less than or equal to
|
c)
Logical operators
Logical operators such as AND, OR,
NOT, NAND, NOR and XOR perform logical operations. The result of the logical
operation would be either true or false and decide the flow of a program.
d)
Functional operators
The built-in functions such ABS,
INT, FIX, left$ etc perform arithmetic
and string operations.
10.9 modes of operations
a) Direct mode
In the direct mode, program statements are entered without a
line number. The computer will execute it as soon as the <return> or
<enter> key is pressed after typing, output is displayed on the screen
10.10 Print command
The print command allows the computer to communicate with
you. Print command is used to display any combination of letters, numbers and
symbols or to evaluate numerical expressions. For example
Print 25+35
Print “BRC Turbat”
b)
indirect mode
the program mode is also called the indirect mode. A program in BASIC
consists of line number followed by an instruction or statement. The statement
with smaller number is executed first.
10.11 let statement
Let
is an assignment statement that stores a value in a location assigned to a
given variable. The general format of the let statement is:-
Line
# let variable = expression
10.12 Comma and Semicolon
A
comma in print statement separates strings and numerical expression.
The
semicolon is used in print statement to separate strings.
10.13 Assignment statements
The
assignment statement is used assign an initial value to a variable or assign a
value as a result of a computation, for example:-
A=10
B=A+50
10.14 Remark statement
The
Rem statement documents the program and provides information to the user about
the program, which may be purpose of program, necessary information for its
execution and its logic for users. Rem statement is non-executable.
10.15 Input statement
Input
statement allows to enter value of a variable while the program is running. The
format of the input statement is :
Line
# input (variable name)
10.16 Read..Data statements
Read…Data
statements are used to assign values. This is useful when the data contains
large number of values. A Data statement contain values of the variables which
are assigned to the respective variable names in Read statement. The format is:
Line
# Read (1st variable, 2nd variable)….
Line
# Data (1st value, 2nd value)….
10.17 Tab function
Tab
function allows us to line up the numbers vertically. The Tab function must be
accompanied by a number enclosed in the parenthesis telling the computer to
move cursor to column specified such as Tab(20).
10.18 Print using statement
Print
using statement allows specifying the appearance and position of numbers. It
also provides a way to round of numbers to a given number of decimal places.
Its format is:
Line # print using
“####.##”
