2.2 Programming

2.2 Programming

1. VARIABLES

   • INPUTS
     • instruction that computer recognises
     • processes instruction using constants and OUTPUTS to user
     • inputs that come from the console/file = parameters
   • shouldn't start with a number or contain spaces
     • names = identifiers
   • CONSTANTS
     • values that DON'T change as program runs
       • uses capital letters
         • simplifies debugging
           • less likely to generate mistakes

2. OPERATORS

   • need correct order for calculations(BODMAS)
   • ARITHMETIC
     • +
       • addition
       • -
         • subtraction
         • /
           • division
           • *
             • muliplication
     • MOD
       • modular division( remainder)
       • DIV
         • integer division
         • ^
           • to-the-power-of
   • BOOLEAN
     • !=
       • not equal to
       • ==
         • equal to
     • AND
       • two conditions must be true for statement to be true
       • OR
         • at least one condition must be true
         • NOT
           • inverts the result e.g. NOT(A and B) will only be false when both A and B are true
   • STRING
     • LEFT("monkey",4) is "monk"
       • SLICING
       • LEN("monkey")[=6]
         • LENGTH
         • monkey.uppercase
           • CHANGE CASES
           • .lowercase
   • FORMATTING
     • ASCII and UNICODE
       • ASCII("c")
       • SPACE
         • NewLine, TAB 4 or 5 spaces

3. SEQUENCES

   • DISADVANTAGES
     • not efficient
       • becomes difficult to follow with large programs
         • extremely hard to maintain
     • ADVANTAGES
       • each line follows the next
         • create simple programs quickly
           • easy to follow for a small program

4. SELECTION

   • use boolean for more complex conditions
     • SELECT CASE can also use boolean operators
       • its columnar nature makes nested select case statements rare
         • switch statements
   • NESTED SELECTION
     • we can only evaluate a condition if some pre-condition is met
       • need two selection statements, one inside the other
         • outside selection is the pre-condition
           • inside selection is condition