11.3: Flowcharting

Flowcharting Symbols

Terminal

The rounded rectangles, or terminal points, indicate the flowchart's starting and ending points.

Figure \(\PageIndex{1}\)

Process

The rectangle depicts a process such as a mathematical computation, or a variable assignment.

Note: the C++ language equivalent is the statement.

Figure \(\PageIndex{2}\)

Input/Output

The parallelograms designate input or output operations.

Note: the C++ language equivalent is cin or cout.

Figure \(\PageIndex{3}\)

Connectors

Sometimes a flowchart is broken into two or more smaller flowcharts. This is usually done when a flowchart does not fit on a single page, or must be divided into sections. A connector symbol, which is a small circle with a letter or number inside it, allows you to connect two flowcharts on the same page. A connector symbol that looks like a pocket on a shirt, allows you to connect to a flowchart on a different page.

On-Page Connector

Figure \(\PageIndex{4}\)

Off-Page Connector

Figure \(\PageIndex{5}\)

Decision

The diamond is used to represent the true/false statement being tested in a decision symbol.

Figure \(\PageIndex{6}\)

Module Call

A program module is represented in a flowchart by rectangle with some lines to distinguish it from process symbol. Often programmers will make a distinction between program control and specific task modules as shown below.

Note: C++ equivalent is the function.

Local module: usually a program control function.

Figure \(\PageIndex{7}\)

Library module: usually a specific task function.

Figure \(\PageIndex{8}\)

Flow Lines

Note: The default flow is left to right and top to bottom (the same way you read English). To save time arrowheads are often only drawn when the flow lines go contrary the normal.

Figure \(\PageIndex{9}\)

Examples

We will demonstrate various flowcharting items by showing the flowchart for some pseudocode.

Functions

Pseudocode: Function with no parameter passing
Function clear monitor
  Pass In: nothing
  Direct the operating system to clear the monitor
  Pass Out: nothing
Endfunction 

Figure \(\PageIndex{10}\)

Pseudocode: Function main calling the clear monitor function
Function main
  Pass In: nothing
  Doing some lines of code
  Call: clear monitor
  Doing some lines of code
  Pass Out: value zero to the operating system
Endfunction 

Figure \(\PageIndex{11}\)

Sequence Control Structures

The next item is pseudocode for a simple temperature conversion program. This demonstrates the use of both the on-page and off-page connectors. It also illustrates the sequence control structure where nothing unusually happens. Just do one instruction after another in the sequence listed.

Pseudocode: Sequence control structure
Filename: Solution_Lab_04_Pseudocode.txt
Purpose:  Convert Temperature from Fahrenheit to Celsius
Author:   Ken Busbee; © 2008 Kenneth Leroy Busbee
Date:     Dec 24, 2008

Pseudocode = IPO Outline

input
  display a message asking user for the temperature in Fahrenheit
  get the temperature from the keyboard
processing
  calculate the Celsius by subtracting 32 from the Fahrenheit
  temperature then multiply the result by 5 then
  divide the result by 9. Round up or down to the whole number.
  HINT: Use 32.0 when subtracting to ensure floating-point accuracy.
output
  display the celsius with an appropriate message
  pause so the user can see the answer 

Figure \(\PageIndex{12}\)

Figure \(\PageIndex{13}\)

Selection Control Structures

Pseudocode: If then Else
If age > 17
  Display a message indicating you can vote.
Else
  Display a message indicating you can't vote.
Endif 

Figure \(\PageIndex{14}\) If then Else control structure

Pseudocode: Case
Case of age
  0 to 17   Display "You can't vote."
  18 to 64  Display "Your in your working years."
  65 +      Display "You should be retired."
Endcase 

Figure \(\PageIndex{15}\) Case Control Structure

Iteration (Repetition) Control Structures

Pseudocode: While
count assigned zero
While count < 5
  Display "I love computers!"
  Increment count
Endwhile 

Figure \(\PageIndex{16}\) While control structure

Pseudocode: For
For x starts at 0, x < 5, increment x
  Display "Are we having fun?"
Endfor 

The for loop does not have a standard flowcharting method and you will find it done in different ways. The for loop as a counting loop can be flowcharted similar to the while loop as a counting loop.

Figure \(\PageIndex{17}\) For control structure

Pseudocode: Do While
count assigned five
Do
  Display "Blast off is soon!"
  Decrement count
While count > zero 

Figure \(\PageIndex{18}\) Do While control structure

Pseudocode: Repeat Until
count assigned five
Repeat
  Display "Blast off is soon!"
  Decrement count
Until count < one

Figure \(\PageIndex{19}\) Repeat Until control structure

Definitions

Flowcharting

A programming design tool that uses graphical elements to visually depict the flow of logic within a function.

Process Symbol

A rectangle used in flowcharting for normal processes such as assignment.

Input/Output Symbol

A parallelogram used in flowcharting for input/output interactions.

Decision Symbol

A diamond used in flowcharting for asking a question and making a decision.

Flow Lines

Lines (sometimes with arrows) that connect the various flowcharting symbols.