1 - Programming GapFill

There are four programming constructs, which determine the order and quantity in which instruction executes.  ComputationSequenceSelectionIncrementation involves each instruction executing once, in a fixed order.   IterationSelectionSequenceIncrementation, indicated by keywords such as  'public''until''do''if' and  'case''begin''protected''loop', involves one path being taken through the code where more than one path was available.   RecursionSequenceIterationSelection is the repeated execution of a block of code, which is signified by programming keyworks such as  'if''private''while''end' and  'for''case''default''catch'.  Finally,  computationselectioniterationrecursion is the construct in which a subroutine calls itself.

When a subroutine calls another subroutine, or calls itself, data can be passed to the called subroutine by way of   parametersglobal variablesmember variablesfields.  There are two ways of doing this.  Passing by  valuefieldvariableliteral involves making a copy of the data that's passed in.  Passing by  literalreferencevalueindex involves passing a pointer to the called subroutine – any changes made to this data entail changes being made to the original, as there is no copy.  A subroutine might return a value, in which case it is referred to as a  functionpassprocedureformula.  If it returns no value, it is known as a  procedurecallpassmethod.