defensive design

• anticipating misuse

  • a programmer must try to make sure that what a user enter will not crash / give incorrect result
  • eg. giving the user requirements and 3 tries before it stops
• authentication routines

  • to make sure user is who they say they are
  • eg optical, facial, fingerprint recognition
  • assigned to a user ID and password
  • the password is encrypted and saved in a file
  • when you enter ur user ID the encrypted password is looked up and compared to the one stored
• input validation to make sure program doesn't crash do smth unexpected

  • range check: number / date within sensible range
  • type check: data is right type
  • length check: text not too long / short
  • presence check: checks data has been entered
  • format check: checks format of eg postcode / email is appropriate
  • verification check: eg. re-entering a password to check if user typed in what they intended
• maintainability - making program code understandable

  • subroutines: easier to locate the code so it can be amended if required without affecting the rest of the program
  • aim for clarity rather than clever code which is difficult for someone else to understand
  • meaningful variable names
  • use conventions such as camelCase
  • indentation so it's clear where statements within an iteration starts and ends
  • comments: who wrote the program, date, purpose and explanation of code and variables