2.3  Producing robust programs

• defensive design considerations:

• • • input sanitisation

      • cleaning the data on entry - removing spaces and SQL characters

    • input validation

      • • make sure that the data is allowed

        • Type check (is it an Integer or a string, real or Boolean)

        • Presence check (has data been entered)

        • Range Check

        • Format check (eg dd/mm/yy)

        • length check (eg 11 digits for phone number)

    • planning for contingencies

      • • what might go wrong

    • anticipating misuse

      • • what might hackers do?

    • authentication

      • • using user names and passwords

• maintainability:

• sensible names for variables constants and subroutine 

  • • to explain complex parts of the code

• comments

  • • to explain to other programmers or your future self what each section of code does 

• indentation

  • • to show different sections of code like if statements or loops

    • so that related functionality is grouped together

• use subroutines

  • • code is structured and easier to test and to follow