End of a working day

1
End of a working day

• Produce PDL pseudocode corresponding to a single
  function which performs the following tasks
• Suppose its the end of a working day.
• After 6pm on Fridays you go to the Manor Quay.
• If youre driving you drink Coke, if not you
  drink Beamish. At 11.30 you go home and go to
  bed.
• If its not a Friday you work late before going
  home and making dinner. After dinner you watch TV
  and then go to bed.

2
function end_of_a_working_day calculate time and
day of week if Friday and after 6 p.m. go to
the Manor Quay loop if driving drink
Coke else drink Beamish ifend loopend
when its 1130 p.m. go home ifend
3
else work late go home make dinner watch
TV ifend go to bed function end
4
Back to the student marks program

• First Cut
• Structure Chart Student
• 
  Marks
• Valid
  Stored
• Marks
  Ranges
• Accept Calculate
  Generate
• Valid Marks Marks Range
  Graph
• We now produce one low level diagram or PDL
  function for each of these 4 modules

5
PDL for student marks program

• Remember that the program accepts pre-validated
  student marks and produces a graph showing the
  count for each of the ranges 0-10, 11-20,
  21-30, ..., 81-90, 91-100.
• Stated assumptions the marks are input as whole
  numbers, and the graph is to be a bar chart of
  asterisks.
• function Student Marks
• set up data
• valid marks lt- accept valid marks ( )
• stored ranges lt- calculate marks range (valid
  marks)
• generate graph (stored ranges)
• function end

6
PDL for Accept Valid Marks

• function Accept Valid Marks
• set up data
• write How many marks?
• read number of marks
• loop for each mark
• read mark
• if mark valid
• write the entered mark
• store mark
• ifend
• loopend
• return the valid marks
• function end

7
PDL for Calculate Marks Range

• function Calculate Marks Range
• set up data
• loop for each mark
• if mark gt 0 subtract 1 from mark
• divide mark by 10 and ignore decimal
  part
• to find the correct range array
  element
• increment the range array element
• loopend
• return the stored ranges
• function end

8
PDL for Generate Graph

• function Generate_Graph
• set up data
• clear the screen
• write graph title
• loop for each range
• calculate lower and upper boundaries
• if lower boundary 1
• lower boundary 0
• ifend
• display range boundaries
• loop for each star
• write
• loopend
• ifend
• loopend
• function end

9
Notes on PDL

• See Sommerville p126 - 129
• In principle, PDLs may be based on any
  programming language. Ada, a standard high level
  language in the defence industry, was designed
  for readability. It is therefore a good choice as
  a base language for a PDL.
• PDLs, with elements of computer code and
  structured natural language, are a compromise
  between comprehensibility and precision.