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An introduction to flowcharting including the demonstration of functions and various control structures.

Flowcharting symbols

Terminal

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

Process

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

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

Input/output

The parallelograms designate input or output operations.

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

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

Off-Page Connector

Decision

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

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.

Library module: usually a specific task function.

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.

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 monitorPass Out: nothing Endfunction

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Function clear monitor

Pseudocode: function main calling the clear monitor function

Function main Pass In: nothingDoing some lines of code Call: clear monitorDoing some lines of code Pass Out: value zero to the operating systemEndfunction

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Function main

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 CelsiusAuthor: Ken Busbee; © 2008 Kenneth Leroy Busbee Date: Dec 24, 2008Pseudocode = IPO Outline inputdisplay a message asking user for the temperature in Fahrenheit get the temperature from the keyboardprocessing calculate the Celsius by subtracting 32 from the Fahrenheittemperature 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. outputdisplay the celsius with an appropriate message pause so the user can see the answer

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Sequence control structure

Sequence control structured continued

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

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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

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Case control structure

Iteration (repetition) control structures

Pseudocode: while

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

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While control structure

Pseudocode: for

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

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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.

For control structure

Pseudocode: do while

count assigned five DoDisplay "Blast off is soon!" Decrement countWhile count>zero

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Do While control structure

Pseudocode: repeat until

count assigned five RepeatDisplay "Blast off is soon!" Decrement countUntil count<one

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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.

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Source:  OpenStax, Programming fundamentals - a modular structured approach using c++. OpenStax CNX. Jan 10, 2013 Download for free at http://cnx.org/content/col10621/1.22
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