This document discusses modular programming techniques. Modular programming involves separating a program's functionality into independent, interchangeable modules. Each module contains code to perform a specific task. The main advantages of modular programming are that it makes programs easier to design, test, maintain and reuse code. Modules can take the form of sub procedures or function procedures. Sub procedures perform tasks without returning values, while function procedures return a single value. Variables can be shared between modules using common, dim with shared, or shared statements.

1. MODULAR PROGRAMMING
Prepared by: Roshan Maharjan
Modular Programming

2. OVERVIEW
■ Modular programming is a technique of developing software by
separating the functionality of a program into independent
interchangeable modules that are combined together to get the final
working software.
■ Modular programming is a technique used to divide program into many
small, manageable, logical and functional modules or blocks.
■ Modular programming is a software design technique that emphasizes
separating the functionality of a program into independent,
interchangeable modules, such that each contains everything necessary
to execute only one aspect of the desired functionality.
Modular Programming

3. Cont……..
■ Every modular program consist of one main module and one or more
sub modules or procedures.
■ Each module has a unique name.
■ Main module is the top level module in which program entry and exist
takes place.
■ The main module is the controlling section of a modular programming.
■ Sub modules is a block of statement that is used for specific task and is
written under the main module.
■ It allows the user to divide into manageable and functional modules or
blocks with the help of sub procedure and function procedure.
Modular Programming

4. Cont……
■ QBASIC programs consists of one or more modules.
■ A module is a block of statement that solve particular
problem.
■ A module may contain SUB and FUNCTION
procedure, as well as code not part of SUB or
FUNCTION
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5. Modular Programming

6. Advantages
■ Different programmers can design different program modules independently, which is
required in a large and complex program.
■ it is easy to design code and test the program modules independently.
■ It is possible to use a single module in different places which reduces program codes.
■ Reduce redundancy
■ Improving the readability of a program.
■ Program maintenance becomes easier.
■ Saving the time.
■ Encourages re-use of code.
Modular Programming

7. Types of Procedures
■ In QBASIC, a programmer can name a block of code which
can be executed by simply calling out that name.These name
blocks of code are called procedures.
■ The two types of procedures are:
i. SUB Procedure
ii. Function Procedure
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8. SUB Procedure
■ SUB procedure is a block of statements which is identified by
a unique name that performs a specific task.
■ The block of statements is placed with a pair of SUB … END
SUB statements and can be called by its name.
■ A SUB-procedure is a small, logical and manageable
functional part of program which performs specific task and
does not return any value.
Modular Programming

9. Features of SUB Procedures
■ SUB procedure does not return any value.
■ SUB procedure can be recursive.They may call
themselves.
■ Sub procedure do not have data types.
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10. SYNTAX (Parameterized)
■ Declaration
DECLARE SUB <name> (parameter list)
■ Definition
SUB <name> (parameter list)
` procedure variable definitions and
statements
END SUB
■ Calling
CALL <name>(argument list)
Modular Programming

11. SYNTAX(Non Parameterized)
■ DECLARE SUB <name> ()
■ CALL <name>
■ SUB <name>
` procedure variable definitions and
statements
■ END SUB
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12. Declaring SUB Procedure
■ The DECLARE statements is used to declare a SUB
procedure.
■ The syntax for the DECLARE statements is as follows:
DECLARE SUB <name>(parameter list)
Example:
DECLARE SUB AOR(L,B)
Sub procedure AOR with two parameter L and B
DECLARE SUB AOR
Sub procedure AOR with no parameters
Modular Programming

13. Defining a SUB procedure
■ The SUB …… END SUB statements is a procedure statements
that marks the beginning and ending of a sub program.The
syntax is:
SUB <name>(parameter list)
procedure variable definitions and statements
END SUB
Modular Programming

14. Calling a SUB Procedure
■ The CALL statements is used to transfer control to
another procedure, a BASIC SUB program.
■ The syntax is :
CALL <name> (argument list)
Example:
CALL AOR(L,B)
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15. Function Procedure
■ A function procedure is a small, logical and functional part of a program
which performs the specific tasks and it returns a single value to the
main program or calling module.
■ The returned value may be string or number.
■ It is either called by using PRINT statement or storing a returned value
into a variable.
Modular Programming

16. SYNTAX(Parameterized)
■ Declaration
DECLARE FUNCTION <name> (parameter list)
■ Definition
FUNCTION <name> (parameter list)
` procedure variable definitions and statements
<name> = Expression
END FUNCTION
■ Calling
PRINT <name>(argument list)
OR
variable = <name>(argument list)
Modular Programming

17. SYNTAX(Non-Parameterized)
■ Declaration
DECLARE FUNCTION <name> ()
■ Definition
FUNCTION <name>
` procedure variable definitions and statements
<name> = Expression
END FUNCTION
■ Calling
PRINT <name>
OR
variable = <name>
Modular Programming

18. Differences
SUB Procedure Function Procedure
The block of statements placed under SUB/END SUB
statements and can be called by its name.
The block of statements placed under
FUNCTION/END FUNCTION statements and can be
invoked from the reference of the function name.
It does not return any value to the calling module It returns a single value to calling module.
It does not have any datatype in its name. It have datatype in its name which is the return value
of a function.
Modular Programming

19. ARGUMENTAND PARAMETER
■ The constants or variables enclosed in the parentheses are supplied to a procedure are
known as Arguments.
■ Argument are also known as Actual Parameter.
■ The variables in a procedure which accepts data or variable passed to them from the
calling module are known as Parameters.
■ Parameter are also known as Formal Parameter.
Modular Programming

20. LOCAL AND GLOBALVARIABLE
■ A variable which is declared inside a module and cannot be accessed by other module
is known as local variable.
■ All variables that are declared either implicitly or explicitly without using SHARED
attribute are local variable.
■ The variable in main module which ca be accessed from any module or procedure of a
program is known as Global variable.
■ A Global variable is declared in the main module by two methods.
Modular Programming

21. 1. Declaring by using COMMON Statement.
Syntax:
COMMON SHARED Variable list
where,
SHARED indicates that variable are shared with all procedures.
variable list A list of one or more variables to be shared in the program.
e.g. COMMON SHARED A, B, C
2. Declaring using DIM statement.
Syntax:
DIM SHARED variable list
e.g. DIM SHARED A$
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22. SHARINGAVARIABLES DEFINED IN A
MAIN MODULEWITH IN A PROCEDURE
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23. ■ Variables can be shared among parts of a module without making the variables global
by using the SHARED statement.
Syntax:
SHARED variable list
e.g.
DECLARE SUBTEMPERATURE()
INPUT”ENTERTEMPERATURE IN CELCIUS”;C
CALLTEMPERATURE
END
SUBTEMPERATURE
SHARED C
F= 9 * C/5 + 32
PRINT “TEMPERATURE IN FAHRENHEIT”;F
END SUB
Modular Programming

24. Thank you
Modular Programming