1 - Programming GapFill

There are four programming constructs, which determine the order and quantity in which instruction executes.  ComputationSelectionIncrementationSequence involves each instruction executing once, in a fixed order.   IncrementationSelectionSequenceIteration, indicated by keywords such as  'public''if''until''do' and  'loop''begin''case''protected', involves one path being taken through the code where more than one path was available.   IterationSelectionSequenceRecursion is the repeated execution of a block of code, which is signified by programming keyworks such as  'end''if''while''private' and  'default''catch''for''case'.  Finally,  iterationrecursioncomputationselection 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   member variablesparametersglobal variablesfields.  There are two ways of doing this.  Passing by  fieldvaluevariableliteral involves making a copy of the data that's passed in.  Passing by  indexreferencevalueliteral 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  formulapassfunctionprocedure.  If it returns no value, it is known as a  methodprocedurecallpass.