CS 240 Computer Programming 1

CS 240Computer Programming 1 Flowcharts

Algorithm a step-by-step method for solving a problem or doing a task. An informal definition of an algorithm is:

Algorithm A 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.

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)

Tools There are two commonly used tools to help to document program logic (the algorithm) Flowcharts Pseudo code

Flowchart Definition The production flowchart is a visual representation of the sequence of the program. It shows what comes first, second, third, etc A flowchart indicates: The steps to be taken in order to solve a problem. The order or the sequence of these steps.

Flowchart Rules 1. 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.

Symbols

1.Simple sequential Flowchart Example 1 Construct a flow chart that prints "Hello, World"?

1.Simple sequential Flowchart Algorithm Step 1- Start Step 2- Print "Hello, World" Step 3- Stop

1.Simple sequential Flowchart Flowchart Start Print “Hello, World” Stop

1.Simple sequential Flowchart Example 2 Construct a flow chart that finds the sum of two numbers.

1.Simple sequential Flowchart Algorithm Variables Step 1- Start A: First Number Step 2- Read A B: Second Number Step 3- Read B C: Sum (A+B) Step 4- Calculate C = A+B Step 5- Print C Step 6- Stop

1.Simple sequential Flowchart Start Flowchart Read A Read B C= A+B Print C Stop

1.Simple sequential Flowchart Example 3 Construct a flow chart that finds the sum, average and product of three numbers.

1.Simple sequential Flowchart Algorithm Variables Step 1- Start X: First Number Step 2- Read X, Y, Z Y: Second Number Step 3- CalculateS = X+Y+Z Z: Third Number Step 4- Calculate A = S/3 S: Sum (X+Y+Z) Step 5- Calculate P = X*Y*Z A: Average (S/3) Step 6- Print S, A, P P: Product (X*Y*Z) Step 7- Stop

1.Simple sequential Flowchart Start Flowchart Read X,Y,Z S= X+Y+Z A=S/3 P=X*Y*Z Print S,A,P Stop

1.Simple sequential Flowchart Example 4 Construct a flow chart that finds the difference and the division of two numbers and display the result

1.Simple sequential Flowchart Algorithm Variables Step 1- Start N1 : First Number Step 2- Read N1, N2 N2 : Second Number Step 3- CalculateD = N1-N2 D: Difference Step 4- Calculate V = N1/N2 V: Division Step 5- Print D,V Step 6- Stop

1.Simple sequential Flowchart Start Flowchart Read N1, N2 D= N1 –N2 V=N1/N2 Print D,V Stop

1.Simple sequential Flowchart Example 5 Exercise Construct a flow chart that finds the circle area and circumference of a circle where R (radius) is given

1.Simple sequential Flowchart Algorithm Variables Step 1- Start R : Radius Step 2- Read R PI: PI = 3.14 Step 3- CalculateA = PI*(R)2 A: Area Step 4- Calculate C = 2*PI*R C: Circumference Step 5- Print R, A, C Step 6- Stop

2. Branched Flowcharts Example 1 Construct a flow chart for the following function F(x) = { X X>=0 -X X<0

2. Branched Flowcharts Algorithm Variables Step 1- Start X : Number Step 2- Read X F: function of X Step 3- if X >=0 then F =X Step 4- if X <0 then F =-X Step 5- Print F Step 6- Stop

2. Branched Flowcharts Start Flowchart Read X YES NO X>=0 F=-X F=X Print F Stop

2. Branched Flowcharts Example 2 Trace the following flowchart and write the output of it. 1. When X = 20 2. When X = -10

2. Branched Flowcharts Start Flowchart >0 0> Read X =0 W=SIN(X)+5 X? W=2*X-1 W=X+1 Print X,W Stop

2. Branched Flowcharts Result When X=-10 When X=20 X= -10 W= -21 X= 20 W= 21

2. Branched Flowcharts Example 3 Exercise Draw a flowchart that shows the traffic light processing

2. Branched Flowcharts Algorithm Variables Step 1- Start C : Traffic light color Step 2- Read C Step 3- make a Decision (what is c) Step 4- if C is RED then Print STOP Step 5- if C is YELLOW then Print WAIT Step 6- if C is GREEN then Print PASS Step 7- Stop

3. Loop Flowcharts Example 1 Trace the following flowchart and write the output of it.

3. Loop Flowcharts Start Flowchart N=1 Print N F T While N>=7 Stop N=N+3

3. Loop Flowcharts Result

3. Loop Flowcharts Example 2 Trace the following flowchart and write the output of it.

3. Loop Flowcharts Start Flowchart i=0 Sum=0 F T While i<10 Read X avg=Sum/10 Print avg Sum= X + Sum Increment i Stop

3. Loop Flowcharts Result Avg=50/10 =5

CS 240 Computer Programming 1