Pascal Programming by dffhrtcv3

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									Pascal
Programming

Records, Stacks & Queues
Pascal Programming

 Record data types—a complex type that
  combines different data types into a
  single record.
 Sometimes called set types.
 The individual elements of a record are
  called fields or components or
  component fields.
Pascal Programming

 Each field has a name . . .the field identifier.
 The field identifiers provide a means of
  accessing each field in the record, similar to
  an array index.
 Each field has a type, which is established
  when the record is declared.
 The value of a record is a collection of values.
  There is a value in each field.
Pascal Programming

 The component of a record variable is a
  component variable.
 . field identifier . . .specifies a
  component variable.
   – e g: Business1.PresidentsLastName
 Though a record is a collection of
  values, it can sometimes be treated as
  a single value.
Pascal Programming

   So . . .
    – The record variable describes the raw
      record.
    – Record value indicates all the values in
      the record.
    – Component values indicate the field
      values.
    – Field identifiers name the fields in record.
Pascal Programming

 Syntax . . .
 type
    – Business =
      • record
         –   BusinessName: string[30];
         –   StreetAddress: string[35]
         –   City: string[20];
         –   State: string[2];
         –   zip: integer;
      • end;
Pascal Programming

 A programmer may want to structure
  data with a hierarchy of records.
 e g:
    – student identification
    – birth date and age
    – core courses . . .etc . . .
Pascal Programming

 Records for a group may be read into
  an array.
 Thus, we see that . . .
    – data structures are a means of
     organizing, storing and manipulating data.
   How do we chose which structure to
    use?
    – Everything being equal, chose the one that can be
      understood and worked with most easily.
Pascal Programming

 If all items are of the same type
  . . .a single array of that type works
  best.
 If items differ in type, use an array
  of records.
 Or, use parallel arrays.
Pascal Programming

 with statements . . .
 With provides instruction(s) to carry out
  an operation.
 Syntax
    – with record_variable_list do
       • statement (usually compound)
   The records_variable_list is separated
    by commas.
Pascal Programming

 Stacks and Queues
 The stack, a specialized data structure,
  compares to a stack of shoe boxes.
 New data goes into a box on the top of
  the stack.
 To read from the stack, access the first
  box, discard it, read the second box,
  discard it etc . . ..
Pascal Programming

 Stacks serves the purpose of reversing
  the order of data -- first in, last out.
 e g: stacktop = (TopValue) -1 . . . This
  creates a decrementation of the stack.
   The text illustrated using the stack to match
    parenthesis. Find and save a left parenthesis
    then look for the right one, eliminate all
    characters in between. Cry fowl when a left
    parenthesis occurs again without a right one.
Pascal Programming

 Queue . . . A data structure for first
  in/first out data handling. The opposite
  of the stack.
 Like a waiting line . . .first come . . .first
  served.
 A queue can be implemented so that as
  the array empties and reaches the end
  the beginning fills again. It becomes
  circular.
Pascal Programming

 Pascal Sets
 Sets contain data like a list but that data
  is unordered.
 To use sets in a variable, we use set
  types
 The ordinals in the sets are its
  elements.
 These are the Base_type of the set.
Pascal Programming

 Example
 type
    – Grade = set of 0 .. 100;
   constant
    – superior: grade = [94 .. 100]
   The first illustrates the declaration of a
    set and the second the appending of a
    typed constant.

								
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