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CS 240COMPUTER

PROGRAMMING 1

Flowcharts

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ALGORITHMAn informal definition of an algorithm is:

a step-by-step method for solving a problem or doing a task.

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ALGORITHMA step-by-step problem-solving procedure

An algorithm is a sequence of unambiguous instructions for solving a problem.

The number of steps of an algorithm will be countable and finite.

It is a sequence of instructions (or set of instructions) to make a program more readable; a process used to answer a question.

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HOW TO UNDERSTAND THE PROBLEM?Define the problem

Analyze the problem

Develop an algorithm/method of solution

Write a computer program corresponding to the algorithm

Test and debug the program

Document the program (how it works and how to use it)

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TOOLS

Flowcharts

There are two commonly used tools to help to document program logic (the algorithm)

Pseudo code

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FLOWCHART

The production flowchart is a visual representation of the sequence of the program. It shows what comes first, second, third, etc

Definition

A flowchart indicates:The steps to be taken in order to solve a

problem.The order or the sequence of these steps.

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FLOWCHART RULES1. Use only one start and one stop per flowchart, --that is, one way in and one way out of the flowchart.

2. The logic flow of the solution is displayed from top to bottom and from left to right.

3. Use the appropriate symbol for each type of operation.

4. Use arrows when moving to another part of the flowchart rather than lines.

5. Do not leave dead-ends--that is, a part of a question unanswered.

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SYMBOLSSymbol Description

   TERMINAL - To start or end a flowchart

 INPUT / OUTPUT - Used with Read, Input, Print and other I/O commands.PROCESSING - Used for operations done inside the computer. Such as calculations, storing and moving of data.

DECISION - Used to ask a question in programming. Questions are Yes/No format (Used with the If Statement).

   

 DIRECTION FLOW - Used to connect symbols and to represent the direction of flow. Lines should not cross each other. Arrowheads should be placed at the end close to the symbol. 

Connector - or joining of two parts of program

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1.SIMPLE SEQUENTIAL FLOWCHART

Construct a flow chart that prints "Hello, World"?

Example 1

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1.SIMPLE SEQUENTIAL FLOWCHART

Step 1- Start

Algorithm

Step 2- Print "Hello, World"Step 3- Stop

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1.SIMPLE SEQUENTIAL FLOWCHART

Start

Print“Hello, World”

Stop

Flowchart

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1.SIMPLE SEQUENTIAL FLOWCHART

Construct a flow chart that finds the sum of two numbers.

Example 2

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1.SIMPLE SEQUENTIAL FLOWCHART

C: Sum (A+B)

Variables

B: Second Number

A: First Number

Step 3- Read B

Algorithm

Step 2- Read A

Step 1- Start

Step 4- Calculate C = A+BStep 5- Print CStep 6- Stop

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1.SIMPLE SEQUENTIAL FLOWCHART Flowchart Start

Read A

Read B

C= A+B

Print C

Stop

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1.SIMPLE SEQUENTIAL FLOWCHART

Construct a flow chart that finds the sum, average and product of three numbers.

Example 3

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1.SIMPLE SEQUENTIAL FLOWCHART

Z: Third Number

Variables

Y: Second Number

X: First Number

Step 3- Calculate S = X+Y+Z

Algorithm

Step 2- Read X, Y, Z

Step 1- Start

Step 4- Calculate A = S/3

Step 6- Print S, A, PStep 7- Stop

S: Sum (X+Y+Z)

A: Average (S/3)

P: Product (X*Y*Z)

Step 5- Calculate P = X*Y*Z

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1.SIMPLE SEQUENTIAL FLOWCHART Flowchart Start

Read X,Y,Z

S= X+Y+ZA=S/3

P=X*Y*Z

Print S,A,P

Stop

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1.SIMPLE SEQUENTIAL FLOWCHART

Construct a flow chart that finds the difference and the division of two numbers and display the

result

Example 4

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1.SIMPLE SEQUENTIAL FLOWCHART

D: Difference

Variables

N2 : Second Number

N1 : First Number

Step 3- Calculate D = N1-N2

Algorithm

Step 2- Read N1, N2

Step 1- Start

Step 4- Calculate V = N1/N2

Step 6- Stop

V: DivisionStep 5- Print D,V

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1.SIMPLE SEQUENTIAL FLOWCHART Flowchart

Start

Read N1, N2

D= N1 –N2V=N1/N2

Print D,V

Stop

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1.SIMPLE SEQUENTIAL FLOWCHART

Construct a flow chart that finds the circle area and circumference of a circle where R (radius) is given

Example 5 Exercise

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1.SIMPLE SEQUENTIAL FLOWCHART

A: Area

Variables

PI: PI = 3.14

R : Radius

Step 3- Calculate A = PI*(R)2

Algorithm

Step 2- Read R

Step 1- Start

Step 4- Calculate C = 2*PI*R

Step 6- Stop

C: Circumference

Step 5- Print R, A, C

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2. BRANCHED FLOWCHARTS

Construct a flow chart for the following function

Example 1

F(x) = { XX>=0-X X<0

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2. BRANCHED FLOWCHARTS

Variables

X : Number

Step 3- if X >=0 then F =X

Algorithm

Step 2- Read X

Step 1- Start

Step 4- if X <0 then F =-X

Step 6- Stop

Step 5- Print F

F: function of X

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2. BRANCHED FLOWCHARTS

FlowchartStart

Read X

Print F

Stop

F=-X F=XX>=

0YESNO

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2. BRANCHED FLOWCHARTS

Trace the following flowchart and write the output of it.

Example 2

1. When X = 20

2. When X = -10

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2. BRANCHED FLOWCHARTS

FlowchartStart

Read X

Print X,W

Stop

W=2*X-1 W=X+1X? >00>

=0W=SIN(X)

+5

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2. BRANCHED FLOWCHARTS

Result

X= 20W= 21

When X=20

X= -10W= -21

When X=-10

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2. BRANCHED FLOWCHARTS

Draw a flowchart that shows the traffic light processing

Example 3 Exercise

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2. BRANCHED FLOWCHARTS

Variables

C : Traffic light color

Step 4- if C is RED then Print STOP

Algorithm

Step 2- Read C

Step 1- Start

Step 5- if C is YELLOW then Print WAIT

Step 7- StopStep 6- if C is GREEN then Print PASS

Step 3- make a Decision (what is c)

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3. LOOP FLOWCHARTS

Trace the following flowchart and write the output of it.

Example 1

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3. LOOP FLOWCHARTSFlowchart Start

StopN=N+3

While N<=7

F

T

N=1

Print N

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3. LOOP FLOWCHARTS

Result

N Loop1 14 27 3

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3. LOOP FLOWCHARTS

Trace the following flowchart and write the output of it.

Example 2

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3. LOOP FLOWCHARTSFlowchart Start

Print avg

StopSum= X + Sum

Increment i

avg=Sum/10

While i<10

F

T

i=0Sum=0

Read X

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3. LOOP FLOWCHARTS

ResultLoop Read X Sum i1 3 3 12 4 7 23 1 8 3

4 10 18 45 7 25 56 5 30 67 3 33 78 8 41 89 4 45 910 5 50 10

Avg =50/10 =5