2. Flowcharts vs Pseudocode
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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3. Rules for Pseudocode
Write only one statement per line
Capitalise initial keyword
Indent to show hierarchy and structures
End multiline structures
Keep statements language independent
Remember you are describing a logic plan to develop
a program, you are not programming!
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4. One Statement Per Line
Each statement in pseudocode should express
just one action for the computer.
Note capitals for the initial keywords
Pseudocode
READ name, hoursWorked, payRate
gross = hoursWorked * payRate
WRITE name, hoursWorked, gross
These are just a few of the keywords to use,
others include
READ, WRITE, IF, ELSE, ENDIF, WHILE, ENDWHILE
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5. Indent to Show Hierarchy
Sequence:
Keep statements in sequence all starting in the same column
Selection: READ name, grossPay, taxes
IF taxes > 0
IF, ELSE (or ELSEIF), ENDIF
net = grossPay – taxes
must be in line
ELSE
Indent all statements that depend net = grossPay
on a condition ENDIF
Loop: WRITE name, net
count = 0
WHILE, ENDWHILE
WHILE count < 10
Indent statements that fall inside ADD 1 to count
the loop but not keywords that WRITE count
form the loop ENDWHILE
Also REPEAT, UNTIL WRITE “The End”
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6. The Selection Structure
yes no
amount < 100
interestRate = .06 interestRate = .10
IF amount < 100
interestRate = .06
Pseudocode ELSE
InterestRate = .10
ENDIF
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7. The Looping Structure
In flowcharting one of the more confusing things
is to separate selection from looping. This is
because each structure use the diamond as their
control symbol.
Pseudocode avoids this by using specific
keywords to designate looping
WHILE / ENDWHILE: condition checked before loop
REPEAT / UNTIL: condition checked after loop
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8. WHILE / ENDWHILE
Start
count = 0
WHILE count < 10
ADD 1 to count
count = 0
WRITE count
ENDWHILE
WRITE “The End”
count
Mainline
<10
Modular
count = 0
Write WHILE count < 10
add 1 to “The End”
count DO Process
ENDWHILE
Stop
write count WRITE “The End”
Process
ADD 1 to count
WRITE count
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9. REPEAT / UNTIL
Start count = 0
REPEAT
count = 0
ADD 1 to count
WRITE count
UNTIL count >= 10
add 1 to WRITE “The End”
count
Mainline
Modular
write count count = 0
REPEAT
DO Process
count
<10 UNTIL count >= 10
WRITE “The End”
Write Process
“The End”
ADD 1 to count
Stop WRITE count
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10. Flowchart vs Pseudocode
Flowchart Advantages: Pseudocode Advantages
Standardized Easily modified
Visual Implements structured
concepts
Done easily on Word
Processor
Flowchart Disadvantages: Pseudocode
Hard to modify Disadvantages:
Structured design elements Not visual
not implemented No accepted standard, varies
Special software required from company to company
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11. Access of Data
The READ statement tells the computer to get a
value from an input device and store it in a memory
location.
How to deal with memory locations which have been
allocated an address e.g. 19087
Give them names (field or variable names)
Using descriptive words e.g. Total as opposed to a
location addresses
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12. Rules for Variable Names
Begin with lowercase letter
Contain no spaces
Additional words begin with capital
Unique names within code
Consistent use of names
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13. Working with Fields
Calculations Selection
+ add > greater than
- subtract < less than
* multiply = equal to
/ divide >= greater than or equal to
** or ^ exponentiation <= less than or equal to
() grouping <> not equal to
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