Logic and languauges

Logic and languauges

1. logic diagrams and truth tables

   • Binary situations
     • either off or on, 1 or zero ;only 2 options
     • An and gate is when 2 conditions both have to be true at one time like a safe with two keys that habve to be turned at once
     • or gates only require one condition to be right like a phone with either a pin or fingerprint
     • Not gates work with true or false and switch true or false
   • Boolean
     • And, or and not gates are boolean functions; they all output true or false
   • A truth table shows all possible combinations of true and false for a gate.
     • Eg an and gate with 2 inputs has 4 possible outcomes yet has 4 input sets.
     • An add gate requires both conditions to output a 1 and or gate requires 1 and a not gate switches true and false.
   • more logic
     • Numbers can output logic such as 7>3 is true.
     • All circuits are made using logic gates in many ways such as an or gate leading into an and gate and then a not gate.
     • embedded systems use logic gates such as movement activeted night like saying if movement is decected and tine > 8 lights on for examnple.

2. Defensive design

   • Defensive design considerations
     • User input
       • inputting fall backs for incorrect data eg dog in an age area
       • preventing program crashes when incorrect data is entered
         • type check e.g. integer or string.
           • You can also use checks to help in other criteria e.g, making sure a password is a certain length or contains so many of each type of character
       • reasonable data e.g. not 4 as a name
     • authentication
     • planning for misuse
     • contigencies
   • simple validation routines
   • simple authentication routines