producing robust programs

producing robust programs

1. creating hard to break programs

2. defensive design

   • protection against unexpected user inputs
     • enter numbers instead of letters
     • validation
       • check data is sensible and reasonable
         • type check : data type
           • length check: right length (1-32 char)
             • format check : certain pattern
               • range check : umber falls between 2 limits
                 • presence check: not blank
   • maintainability
     • code is understandable
       • reduce chance of coding mistakes/ bugs
     • use
       • comments, indentations, formatting (subroutines)
       • naming conventions
         • constants
   • minimising/ removing bugs
     • testing
       • functions as designed
         • meets needs of user
       • iterative testing
         • over and over throughout coding before moving on
           • in sections
       • final/ terminal testing
         • at end of development
           • tested as a whole
       • valid data- expected results
       • invalid data- produce an error
       • borderline - valid but on edge of what's ok
   • authentication
     • e.g: username and password (access rights)
     • right people, right access
     • update password regularly, complex password, limit login attempts