EEE 243B Applied Computer Programming 11 - Flowcharts §Appendix C Sylvain P. Leblanc

EEE 243BApplied Computer Programming

11 - Flowcharts§Appendix C

Sylvain P. Leblanc

Review• What are the three ways to use the name

of a function in a program?• Are identifiers required for the parameters

in a function prototype?• Can you use a void function in an

assignment expression? • Why/Why not

• What information does the type of a variable give us?

Winter 2011 2Prof S.P. Leblanc

Outline

1. Representing Program Behaviour2. Flowchart Evolution and Motivation3. Flowchart Symbols

a. Auxiliaryb. Primary

4. Flow Control Flowchartsa. if-elseb. switchc. ford. whilee. do…while

5. Flowcharts and EEE243

3Winter 2011 Prof S.P. Leblanc

1. Representing Program Behaviour• In the lectures 08 and 09, we have seen

flow of control structures: functions, if-else, else-if, switch, while, for and do-while

• There are several methods to represent the logic behind the use of these constructs• Pseudo code – English like statements• Flowcharts – Graphical • Chapin diagrams – Graphical


5Prof S.P. Leblanc

Flowcharts vs. Structure Charts• The Structure Charts that we discussed

with functions are also a graphical method, but they are different:• Structure Charts describe the hierarchical

organization• Flow Charts describe the behaviour

• In Flowcharts, each of the flow control constructs can be graphically represented• Regardless if you use OOAD or structured

programming, flowcharts can help you visualize the logic flow of a program

Winter 2011

6Prof S.P. Leblanc

2. Flowchart Evolution• Flowcharts used to be the main design tool

for symbolic languages to represent the logic flow of a program

• Flowcharts fell out of grace when new analysis and design techniques emerged• Flowcharts were seen as not scalable for large

scale designs• Before diagrammatic tools, flowcharts

were drawn by hand using stencils

Winter 2011

2. Flowchart Evolution• The production of these charts was

tedious, and for large monolithic programs, they were difficult to manage• For large programs it used to be common to

see “wall flowcharts”• So why do we still use them?

• Our programs are no longer huge monolithic lines of assembler code

• We decompose our problems into manageable parts (functions)


2. Flowcharts Motivation

• Flowcharts are now used to describe the inside of functions; not the entire program• A flowchart shows an algorithm – a way to

solve a problem• The flowchart frees the programmer from

the syntax and details of the programming language and allows him to concentrate on the details of the problem to be solved

• A pictorial representation of our programs allows us to think more clearly• There are several software tools that you can

use to draw flowcharts. • PowerPoint was used for all these charts• Visio also has this capability


3a. Flowcharts – Auxiliary Symbols

• We will not cover all the symbols here, we covered the main symbols that you will need to produce algorithms

• Terminal symbol – shows start and end of algorithms

• Flow lines – Shows the order of actions

• Connector – Shows connecting points in algorithm:• When we reach the end of a page or column,• When we want to show something that does

not fit in the flowWinter 2011 9Prof S.P. Leblanc

Start

n

3b. Flowcharts – Primary Symbols

• Assignment Statements

• I/O Statements

• Call to a function in another module

• Compound Statement


sum = a + bmult = a * b

READ (a)

x abs()from math.h

4a Flowcharts – if-else


a > 10

SomethingSomething

else

T F

4a Flowcharts – switch


a ?

Somethingm

Something0

Somethingn

m n o

4. Flowcharts - for


Initial conditionCondition

Update

Something

T

F

4. Flowcharts – while


Condition

Something

T

F

4. Flowcharts – do…while


T

F

Something

Condition

5. Flowcharts in EEE243• Note that you will be required to create a

flowchart to hand in for one of your labs• I recommend flowcharting to capture solution

you develop when faced with a problem• Step 4 in the structured design procedure we

covered in lecture 04• Flowcharts are at the same conceptual level a

C code• But flowcharts make it easier to see the algorithm ..

It represents a different abstraction• Most student’s generate their flow chart

afterwards instead of using it as a design tool• That’s a mistake!• Practice with flow charting, and complex problems

will become easier to solve.Winter 2011 16Prof S.P. Leblanc

Quiz Time

• Why are flow charts useful?


Next Lecture• Arrays and Command Line Arguments


Documents

EEE 243B Applied Computer Programming 11 - Flowcharts §Appendix C Sylvain P. Leblanc