CHAPTER 3:
MODULARIZATION
Objectives
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Understanding Documentation
Learn about documentation
Learn about the advantages of modularization
Learn how to modularize a program
Declare local and global variables and constants
Create hierarchy charts
Documentation
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Documentation
 All
supporting material that goes with a program
 Two major categories: for users and for programmers
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User Documentation: End users (people who use
computer programs)
Program Documentation
 Internal
program documentation: comments within code
 External program documentation: supporting
paperwork written before programming begins
Output Documentation
Figure 3-2 Inventory records
displayed in a GUI environment
Figure 3-3 Inventory records
displayed in a running program
Input Documentation
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Describes what input is available to produce the
output
File description:
 Describes
data stored in a file
 Indicates fields, data types, and lengths
Figure 3-6 Inventory file description
Completing Documentation
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Program documentation may contain:
– Output design
– Input description
– Flowcharts
– Pseudocode
– Program code listing
User documentation may contain:
– Manuals
– Instructional material
– Operating instructions
Modularization
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Modularization: breaking a large program into
modules
Advantages of modularization:
 Provides
abstraction
 Allows multiple programmers to work simultaneously
 Allows code reuse
 Makes identifying structures easier
Modularization
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Module:
 Unit
of code that performs one small task
 Called a subroutine, procedure, function, or method
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Invoke (call) a method is to execute it
Calling method invokes the called method
Program contains unlimited number of methods
 Each
method can be called unlimited number of times
Modularization Provides Abstraction
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Focuses on important properties while ignoring nonessential details
Avoids low-level details
Makes complex tasks look simple
High-level programming languages allow English-like
vocabulary
 One statement corresponds to dozens of machine
instructions
Modules provide another way to achieve abstraction
Modularization Provides Abstraction
(continued)
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To-do list with abstraction
Do laundry
Call Aunt Nan
Start term paper
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To-do list without
abstraction
Pick up laundry
basket
Put laundry basket in
car
Drive to laundromat
Get out of car with
basket
Walk into laundromat
Set basket down
. . .
Modularization Allows Multiple
Programmers to Work on a Problem
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Commercial programs rarely written by a single
programmer
Development time is significantly reduced
Large programming projects can be divided into
modules
Modules can be written by different programmers
or programming teams
Modularization Allows You to
Reuse Your Work
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Subroutines that are useful should be used more
than once in a program
 Example:
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routine that checks the current date
Instructions placed in their own module are easy to
port to other applications
Reusability: the ability to use modules in a variety
of applications
Reliability: assurance that a module has been
tested and proven to function correctly
Reliable software saves times and money
Modularizing a Program
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Most programs contain a main program
Contains the mainline logic
 Accesses other modules or subroutines
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Rules for naming modules different for every
programming language
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For this text:
 Must
be one word
 Should be meaningful
 Followed by a set of parentheses
 Corresponds to module naming in Java, C++, C#
Modularizing a Program (continued)
Table 3-1 Suggested identifiers for a module that calculates
an employee’s gross pay
Modularizing a Program (continued)
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Calling program (or calling module): one that uses
another module
Flowchart symbol for calling a module: rectangle with
bar across the top
Flowchart for the module
 Start
symbol: contains module name
 Stop symbol: contains exit or return
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When a module is called, logic transfers to the model
When module ends, logic transfers back to the caller
Figure 3-8 Sample logic
Figure 3-9 Logic from Figure 3-8
using a method
Figure 3-10 Logic from Figure 3-9 using two methods
Modularizing a Program (continued)
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Method is encapsulated in another method if it is
contained in another method
Knowing when to break a module into its own
subroutines or submodules is an art
Best practice: place together statements that
contribute to one specific task
Functional cohesion: extent to which the statements
contribute to the same task