Pseudocode An Introduction

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Pseudocode An Introduction
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Flowcharts were the first design tool to be
widely used, but unfortunately they do not
reflect some of the concepts of structured
programming very well. Pseudocode, on the other
hand, is a newer tool and has features that make
it more reflective of the structured concepts.
The drawback is that the narrative presentation
is not as easy to understand and/or follow.
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What is Pseudocode?

• Pseudocode is "halfway" between english and a
  programming language.
• It is a description of a process in detail,
  though not necessarily in full sentences.
• The key is to provide enough information so that
  anyone could follow the instructions (a child, an
  alien, or even a computer, if the instructions
  were translated into a language it understands).
• Recipes are one type of pseudocode, instructions
  for assembling things are another.

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Rules for Pseudocode

• Write only one statement per line

• Capitalize initial keyword

• Indent to show hierarchy

• End multiline structures

• Keep statements language independent

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One Statement Per Line

• Each statement in pseudocode should express just
  one action for the computer. If the task list is
  properly drawn, then in most cases each task will
  correspond to one line of pseudocode.

Task List Read name, hours worked, rate of
pay Perform calculations gross hours worked
rate of pay Write name, hours worked, gross
Pseudocode READ name, hoursWorked, payRate gross
hoursWorked payRate WRITE name, hoursWorked,
gross
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Capitalize Initial Keyword

• In the example below note the words READ and
  WRITE. These are just a few of the keywords to
  use, others include
• READ, WRITE, IF, ELSE, ENDIF, WHILE, ENDWHILE

Pseudocode READ name, hoursWorked, payRate gross
hoursWorked payRate WRITE name, hoursWorked,
gross
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Example of Pseudocode for Washing the Dishes

• close the sink drain holesquirt some dish liquid
  in the sinkturn on hot waterWHILE sink is not
  full    wait 2 seconds    splash water to
  create bubblesturn off water(sink is now full
  of hot, soapy water)put a dishrag in the
  sinkWHILE there are dirty dishes    grab a
  dish    put dish in the sink    scrub dish with
  dishrag    IF dish is still dirty        THEN
  scrub dish with scouring pad    rinse dish   
  put dish in draineropen the sink drain holeput
  dishrag in laundry basket
• Drying the dishes is left as an exercise to the
  reader ) Even though this description is fairly
  complex, it still has some pieces missing. If
  there are nonstick dishes, we don't want to
  scratch them with the scouring pad. We don't want
  to wash greasy dishes first, since they will make
  the water dirty. There are no instructions for
  times when the dish drainer is full... The
  pseudocode you write should be detailed enough
  that it can be understood (by a child, alien, or
  computer) without being so detailed that it
  becomes difficult to follow.

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Advantages Disadvantages

• Flowchart Advantages
• Standardized
• Visual

• Pseudocode Advantages
• Easily modified
• Implements structured concepts
• Done easily on Word Processor

• Flowchart Disadvantages
• Hard to modify
• Structured design elements not implemented
• Special software required

• Pseudocode Disadvantages
• Not visual
• No accepted standard, varies from company to
  company

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References

• http//www.cs.indiana.edu/rscherle/a106/lesson3.h
  tml
• http//faculty.ccri.edu/mkelly/COMI1150/Pseudocode
  20Basics.ppt