Lecture-8_ Flowchart Algorithm Pseudocode.pptx

Lecture-8_ Flowchart Algorithm Pseudocode

1. ALGORITHMS AND FLOWCHARTS

2. ALGORITHMS AND FLOWCHARTS A typical programming task can be divided into two phases: Problem solving phase produce an ordered sequence of steps that describe solution of problem this sequence of steps is called an algorithm Implementation phase implement the program in some programming language

3. Steps in Problem Solving First produce a general algorithm (one can use pseudocode ) Refine the algorithm successively to get step by step detailed algorithm that is very close to a computer language. Pseudocode is an artificial and informal language that helps programmers develop algorithms. Pseudocode is very similar to everyday English.

4. Pseudocode & Algorithm Example 1: Write an algorithm to determine a student’s final grade and indicate whether it is passing or failing. The final grade is calculated as the average of four marks.

5. Pseudocode & Algorithm Pseudocode : Input a set of 4 marks Calculate their average by summing and dividing by 4 if average is below 50 Print “FAIL” else Print “PASS”

6. Pseudocode & Algorithm Detailed Algorithm Step 1: Input M1,M2,M3,M4 Step 2: GRADE ← (M1+M2+M3+M4)/4 Step 3: if (GRADE < 50) then Print “FAIL” else Print “PASS” endif

7. The Flowchart (Dictionary) A schematic representation of a sequence of operations, as in a manufacturing process or computer program. (Technical) A graphical representation of the sequence of operations in an information system or program. Information system flowcharts show how data flows from source documents through the computer to final distribution to users. Program flowcharts show the sequence of instructions in a single program or subroutine. Different symbols are used to draw each type of flowchart.

8. The Flowchart An organized combination of shapes, lines and text which graphically illustrate a process/program. A type of diagram that represents an algorithm, workflow or process, showing the steps as boxes of various kinds, and their order by connecting them with arrows. This diagrammatic representation illustrates a solution to a given problem. Emphasizes individual steps and their interconnections Flowcharts are used in analyzing, designing, documenting or managing a process or program. Like other types of diagrams, they help visualize what is going on and thereby help the people to understand a process, and perhaps also find flaws, bottlenecks, and other less-obvious features within it. Very helpful in explaining program to others.

9. Flowchart Symbols Different symbols are used for different states in flowchart, For example: Input/Output and decision making has different symbols. The table below describes most of the symbols that are used in making flowchart

10. Example PRINT “PASS” Step 1: Input M1,M2,M3,M4 Step 2: GRADE ← (M1+M2+M3+M4)/4 Step 3: if (GRADE <50) then Print “FAIL” else Print “PASS” endif START Input M1,M2,M3,M4 GRADE←(M1+M2+M3+M4)/4 IS GRADE<50 PRINT “FAIL” STOP Y N

11. Example 2 Write an algorithm and draw a flowchart to convert the length in feet to centimeter. Pseudocode : Input the length in feet (Lft) Calculate the length in cm (Lcm) by multiplying LFT with 30 Print length in cm (LCM)

12. Example 2 Algorithm Step 1: Input Lft Step 2: Lcm ← Lft x 30 Step 3: Print Lcm START Input Lft Lcm ← Lft x 30 Print Lcm STOP Flowchart

13. Example 3 Write an algorithm and draw a flowchart that will read the two sides of a rectangle and calculate its area. Pseudocode Input the width (W) and Length (L) of a rectangle Calculate the area (A) by multiplying L with W Print A

14. Example 3 Algorithm Step 1: Input W,L Step 2: A ← L x W Step 3: Print A START Input W, L A ← L x W Print A STOP

15. Example 4 Write an algorithm and draw a flowchart that will calculate the roots of a quadratic equation Hint: d = sqrt ( ), and the roots are: x 1 = (– b + d )/2 a and x 2 = (– b – d )/2 a

16. Example 4 Pseudocode : Input the coefficients (a, b, c) of the quadratic equation Calculate d Calculate x 1 Calculate x2 Print x 1 and x2

17. Example 4 Algorithm : Step 1: Input a, b, c Step 2: d ← sqrt ( ) Step 3: x 1 ← (– b + d ) / (2 x a ) Step 4: x 2 ← (– b – d ) / (2 x a ) Step 5: Print x 1, x 2 START Input a, b, c d ← sqrt( b x b – 4 x a x c ) Print x 1 , x 2 STOP x 1 ← (– b + d ) / (2 x a ) X 2 ← (– b – d ) / (2 x a )

18. Example 5 Draw a flowchart to add two numbers entered by user. Start Read a, b End sum ← a + b Declare a, b , sum Print sum

19. Draw a flowchart to print the average of three numbers entered by user. Start Read n1, n2,n3 End sum ← n1 + n2 + n3 avg ← sum / 3 Declare n1, n2 ,n3, sum, avg Example 6 Print avg

20. Example 7 Draw a flowchart to find the largest among three different numbers entered by user.

21. Start Read m End Declare m, counter=0 Print “n” is counter < m Example 8 : Draw a flowchart to print a letter ‘n’ m times. counter=counter+1 F T

22. Algorithm and Pseudo Code Example - 9 Problem 1: Given a list of positive numbers, return the largest number on the list. Inputs: A list L of positive numbers. This list must contain at least one number. (Asking for the largest number in a list of no numbers is not a meaningful question.) Outputs: A number n, which will be the largest number of the list. Algorithm: 1. Set max to 0. 2. For each number x in the list L, compare it to max. 3. If x is larger, set max to x. 4. max is now set to the largest number in the list. Program Segment def find_max (L): max = 0 for x in L: if x > max: max = x return max

23. Example - 10 Add two numbers entered by the user Step 1: Start Step 2: Declare variables num1, num2 and sum. Step 3: Read values num1 and num2. Step 4: Add num1 and num2 and assign the result to sum. sum←num1+num2 Step 5: Display sum Step 6: Stop

24. Example - 11 Find the largest number among three numbers Step 1: Start Step 2: Declare variables a, b and c. Step 3: Read variables a, b and c. Step 4: If a > b If a > c Display a is the largest number. Else Display c is the largest number. Else If b > c Display b is the largest number. Else Display c is the greatest number. Step 5: Stop

25. Example - 12 Find the largest number among three numbers Step 1: Start Step 2: Declare variables a, b and c. Step 3: Read variables a, b and c. Step 4: If a > b If a > c Display a is the largest number. Else Display c is the largest number. Else If b > c Display b is the largest number. Else Display c is the greatest number. Step 5: Stop

26. Example - 13 Find the largest number among three numbers Step 1: Start Step 2: Declare variables a, b and c. Step 3: Read variables a, b and c. Step 4: If a > b If a > c Display a is the largest number. Else Display c is the largest number. Else If b > c Display b is the largest number. Else Display c is the greatest number. Step 5: Stop

27. Example - 14 Find the largest number among three numbers Step 1: Start Step 2: Declare variables a, b and c. Step 3: Read variables a, b and c. Step 4: If a > b If a > c Display a is the largest number. Else Display c is the largest number. Else If b > c Display b is the largest number. Else Display c is the greatest number. Step 5: Stop

28. Example - 15 Find the largest number among three numbers Step 1: Start Step 2: Declare variables a, b and c. Step 3: Read variables a, b and c. Step 4: If a > b If a > c Display a is the largest number. Else Display c is the largest number. Else If b > c Display b is the largest number. Else Display c is the greatest number. Step 5: Stop