Pseudocode

• sequential -- one statement after another.
• selection -- picking one (or none) of a set of possible choices
  

            if ( a == 2 )
  	          b = b + 1
            endif
        

• repetition -- doing something zero or more times.

            while ( a < 10 )
  	          c = c + 1
  	          a++;
            end while
        

From the lectures of CMSC104

Generic Algorithm for Cookie Problem

• Get number of children.
• Get number of cookies remaining.
• While there are still children that have not raided the cookie jar,
      multiply the number of cookies by 2 and reduce the number of children by 1.
• Display the original number of cookies.

Pseudocode

• When we broke down the previous problem into steps, we expressed each step as an English phrase.
• We can think of this as writing pseudocode for the problem.
• Typically, pseudocode is a combination of English phrases and formulas.
• Pseudocode is used in
  • designing algorithms
  • communicating an algorithm to the customer
  • converting an algorithm to code (used by the programmer)
  • debugging logic (semantic) errors in a solution before coding (hand tracing)
• Let's write the Cookie Problem algorithm using a more formal pseudocode and being more precise.
  • Display "Enter the number of children: "
  • Read <number of children>
  • Display "Enter the number of cookies remaining: "
  • Read <cookies remaining>

  • While (<number of children>  >  0)
        <cookies remaining> = <cookies remaining> X 2
        <number of children> = <number of children> - 1
    End_While 

  • Display "Original number of cookies = ", <cookies remaining>

Observations

• Any user prompts should appear exactly as you wish the programmer to code them.
• The destination of any output data should be stated, such as in "Display", which implies the screen.
• Make the data items clear (e.g., surround them by < and > ) and give them descriptive names.
• Use formulas wherever possible for clarity and brevity.
• Use keywords (such as Read and While) and use them consistenty. Accent them in some manner.
• Use indentation for clarity of logic.
• Avoid using code. Pseudocode should not be programming language-specific.
• Always keep in mind that you may not be the person translating your pseudocode into programming language code. It must, therefore, be unambiguous.
• You may make up your own pseudocoding guidelines, but you MUST be consistent.