Techniques used in developing well-written code

The use of good programming practice, including:
A Clear Uncluttered Mainline

• Software products should be developed using a clear modular approach
• In general, the mainline should be clear and uncluttered so it is easy to follow and identify subroutine calls
• This means that the subroutines are coded and tested independently which is better for maintenance reasons

One Logical Task Per Subroutine

• The name should be able to describe the algorithm succinctly
• When the algorithm becomes longer than about one page it becomes more difficult to understand and therefore to maintain

Use of Stubs

• A stub is an incomplete function that has the same name and interface as the final form but simpler
• Stubs usually only contains an output statement to indicate the function was called
• Is used in testing the implementation of a program

Appropriate Use of Control Structures and Data Structures

• Control structures should only use recognised statements such as pre or post test loops
• The condition for the loop should determine the only exit from the loop
• There shouldn’t be jumps that cause control to exit a loop or selection unexpectedly
• Types and unusual cases should be considered when making repetition or selection structures
• Data structures such as arrays, records, array of records and others should be selected and designed to assist processing

Writing for Subsequent Maintenance

• Coding should be done in such a way that future maintenance programmers can easily update the code
• Good ways to make the code accessible for maintenance includes:
  • Clear documentation within the code
  • appropriate identifiers names
  • indenting within control structures

Version Control and Regular Backup

• During coding all programmers should regularly save their work to prevent loss and allow for different versions of the program or module
• Regular backup should be done to various devices instead of single one to prevent absolute loss
• Version control allows complete applications to be continuously developed with regular version being released to users
• Version control allows reversion to a previous version any time in the future
• Version control systems are routinely used by teams of programmers because it routinely does all of the above functions

Recognition of Relevant Social and Ethical issues

• Social and ethical issues should be considered when developing
• Some of these include:
  • Intellectual property when code written by others is used
  • Thorough testing to ensure software performs correctly
  • Documentation for future developers and maintainers

The process of detecting and correcting errors, including:
Types of Errors

• Syntax errors
  • Syntax errors are involved in the translation process
  • Syntax errors prevent the translating the high level code to object code
  • Once a syntax error has been detected, it is usually a simple task to correct
• Logic errors
  • Logic errors are the result of syntactically correct code that does not complete the required task
  • Logic errors are the most difficult error to correct
  • It is impossible for the development environment to detect logic errors
• Runtime errors
  • Runtime errors are errors that occur while executing, they can include:
  • Arithmetic errors
    • Involves the incorrect use of data types and data structures
    • Usually occurs when result cannot be stored properly
  • Division by zero
    • Undefined arithmetic operation that causes error
  • Inappropriate memory locations
    • Error occurs when inappropriate memory locations are accessed, eg array range

Methods of Error Detection and Correction

• Use of flags
  • Flags are a marker placed in the code to signal a change in status
  • Code that will change the value of the flag is added to an appropriate location
• Methodical approach to the isolation of logic errors
  • The programmer may use the comment tool to stop code from running
  • Programmers may also comment out blocks of code and systematically find the precise location of an error
• Use of debugging output statements
  • Debugging output statements are temporary lines of code added to display the value of a variable
  • It may also be used to state that a particular part of code has been reached
• Peer checking
  • Involves the checking of the code along with other person/programmer
• Desk checking
  • Test data is used to compare the actual result with the expected results
  • Use structured walk
  • through to step through the code and find where errors occur
  • Deskchecking should be performed on sub and whole programs
• structure walk through
  • structured walk-through are more formal than peer checks
  • No attempt is made to correct problems as they stand but instead get feedback
  • Made to evaluate the design at different levels

The use of software debugging tools
Break Point

• A simple technique which may temporarily or permanently stopping execution
• Used to check variable contents before and after processes occur

Resetting variable contents

• The data stored in a variable can be changed while the program is running
• Can be used to check which values are giving errors

Program traces

• Allows the programmer to view progress of the program execution in detail
• Particularly useful for following the progress of the program through nested loops or complicated selections

Single Line stepping

• A variable trace enables the programmer to observe the variable changing throughout the program