3.5 Maintaining Software Solutions

Modifications to code are often required. These modifications need not be made by the original developers. In these situations, original documentation is very important in understanding the logic used in the solution. Students should be given opportunities to modify their code and to gain experience in modifying the code of others with varying amounts of documentation available. 

Students could be asked to modify solutions as a means of assessing their understanding. Students should be reminded of the ethical issues associated with accessing and modifying the code of others.

Outcomes

A student:

  • P1.2 describes and uses appropriate data types
  • P2.2 describes the effects of program language developments on current practices
  • P3.1 identifies the issues relating to the use of software solutions
  • P4.1 analyses a given problem in order to generate a computer-based solution
  • P4.2 investigates a structured approach in the design and implementation of a software solution
  • P4.3 uses a variety of development approaches to generate software solutions and distinguishes between these approaches
  • P5.1 uses and justifies the need for appropriate project management techniques
  • P5.2 uses and develops documentation to communicate software solutions to others
  • P6.1 describes the skills involved in software development
  • P6.2 communicates with appropriate personnel throughout the software development process
  • P6.3 designs and constructs software solutions with appropriate interfaces.
Student Learns About:

Reasons for maintaining code
  • changing user requirements
  • upgrading the user interface
  • changes in the data to be processed
  • introduction of new hardware or software
  • changing organisational focus
  • changes in government requirements
  • poorly implemented code

Features in source code that improve its
maintainability, including:
  • use of variables instead of literal constants
  • use of meaningful variable names
  • explanatory comments in the code
  • use of standard control structures with appropriate indentation
  • appropriate use of white space to improve legibility of the source code
  • a clear and uncluttered mainline
  • one logical task per subroutine
  • meaningful names for subroutines and modules

Understanding source code

  • reading original documentation in order to understand code
    • documentation for the user (including user manuals)
    • documentation for developers
  • reading original algorithms to identify:
    • inputs
    • the type and purpose of variables used
    • processes
    • outputs
  • creating algorithms for source code when they are not available to aid in understanding
    • identify the control structures that have been used
    • understand how variables have been used
Inclusion of code from other sources
  • copyright issues
  • compatibility of code
Student Learns To:

  • identify and describe features in code that allow it to be easily maintained









  • create solutions that are easy to maintain










  • convert a fragment of source code into its equivalent algorithm
  • define the purpose of the code to be maintained
  • modify code to meet changed requirements








  • provide appropriate acknowledgement of the code of other programmers that has been incorporated as part of the maintenance process
  • assess the compatibility of code to be included in the source code of an existing solution

Modification of code

  • Maintenance is the ongoing upgrading and repair of a program.
  • Producing a software solution of any size that does not need to be changed is almost impossible.
  • It is important to build maintenance into the development process.

Identification of the reasons for change

  • The reasons for software maintenance are categorised into three groups:
    • Corrective maintenance – fix errors
    • Adaptive maintenance – adjust to changes in hardware or other software
    • Improvement maintenance – add functionality

Location of section to be altered

  • Locating either the module or the section of code to be modified is made much easier by:
    • Good quality structure diagrams, data flow diagrams and system flowcharts
    • Internal documentation including comments in the code and intrinsic naming of modules and variables
    • Single logical tasks handled by separate routines 

Determining changes to be made

  • Priority: Is the fault urgent?
  • Extent: How many changes have to be made
  • Personnel: Who will do the changes?
  • Skills and expertise: What skills are needed to complete the changes? Are such skills available?


Implementing and testing

  • Implementation of modifications will usually be simpler than the full implementation of a program.
  • Testing procedures should be rigorous and detailed to ensure that the  changes interact correctly and efficiently with the original code.

Documentation of changes

  • Any modification to the original code needs to be documented in the same detail as the original program.
  • Documentation is of the same nature and extent:
    •  Internal documentation comments in code, intrinsic naming
    •  External documentation: process documentation for future developers and programmers, product documentation for users
    •  This will include modifications of online help, manuals, trouble shooting and installation guides.

Use of CASE tools

  • Tracking changes using CASE tools is not cost effective unless the project is very large.
  • Changes tracked could include:
    • Documentation and versioning of user manuals and developer reports.
    • Data files and data structures using data dictionary tools
    • Modules including the modules identified as reusable and those that have been modified
    • Testing procedures and results including generation of new sets of test data
    • Conflicts and conflict resolution procedures.

 CASE tools for versioning

  • Version numbering is a hierarchical process of keeping track of changes to a program.
  • Some of the CASE tools that support version management are variations of databases keeping records of each new version and the modifications included in the new version.
  • Maintenance is often the largest component of program development.
  • Nearly every program is often the largest component of program development.
  • Nearly every program will require modification
  • Modification is often not made by the original developers
  •  Documentation of all kinds is critical in enabling cost effective maintenance to occur.










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