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MODULARITY By: Andre Mayne

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What Is a Module?

• In software, a module is a part of

a program. Programs arecomposed of one or moreindependently developed modulesthat are not combined until the

program is linked. single modulecan contain one orseveral routines.

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!ystems programming language

•  "riginally used to write #ni$•  %ata types and control structures close to most

machines

•  now also a popular application programming language

 &otable features

•  all functions are call'by'value

•

 Pointer (address) arithmetic•  simple scope structure

•  I*" and memory mgmt facilities provided by libraries

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Why is this better?

• Easier to understand

• +asier to test and debug

• +asier to reuse code• +asier to make changes

Int main ()  char -stringsM/0!12I&3!45Int nstrings52ead!trings(strings, 6nstrings,M/0!12I&3!, stdin)5

!ort!trings(strings,nstrings)5Write!trings(strings,0nstrings, stdout)5return0758

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Why is this etter!

• +asier to understand

• Easier to test and deug

•

+asier to reuse code• +asier to make changes

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Why is this better?

• +asier to understand

•

+asier to test and debug• Easier to reuse "ode

• +asier to make changes

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Why is this better?

• +asier to understand

• +asier to test and debug

•

+asier to reuse code• Easier to #a$e "hanges

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!eparate 9ompilation

Move string array into separate :le

• %eclare interface instringarray.h

• Provide implementation instringarray.c

•

 llows re'use by other programs

stringarray.h+$tern0void02ead!trings(char --strings,int-nstrings,

Int ma$strings, ;I<+ -fp)5

+$tern void Write!trings(char --strings,int nstrings, ;I<+ -fp)5

+$tern void !ort!trings(char --strings,int nstrings)5

+$ternint 9ompare!trings(char -string=, char -string>)5

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bstract0%ata01ypes

 

Module supporting operations on single data structure

  Interface declares operations, not data structure

  Implementation is hidden from client (encapsulation)

  #se features of programming language to ensure encapsulation

9ommon0practice

  llocation and deallocation of data structure handled bymodule

  &ames of functions and variables begin with @modulenameA  Provide as much generality*Be$ibility in interface as possible

  #se void pointers to allow polymorphism

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)u##ary

• Modularity is $ey to good so(t*are

 %ecompose program into modules

 Provide clear and Be$ible interfaces

• Astra"t Data Ty&es

 Modules supporting operations on data structure

 Well'designed interfaces hide implementations, but provide Be$ibility

Advantages

 !eparate compilation

 +asier to understand

 +asier to test and debug

 +asier to reuse code

 +asier to make changes