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# Algorithms and flowcharts

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Algorithms and flowcharts

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### Algorithms and flowcharts

1. 1. Types of OS: Operating System can also be classified as, Single User Systems  Multi User Systems
2. 2. Single User Systems:  Provides a platform for only one user at a time.  They are popularly associated with Desk Top operating system which run on standalone systems where no user accounts are required. Example: DOS 
3. 3. Multi-User Systems:  Provides regulated access for a number of users by maintaining a database of known users.  Refers to computer systems that support two or more simultaneous users.  Another term for multi-user is time sharing.  Ex: All mainframes and are multi-user systems. Example: Unix 
4. 4. Contents  Today's Topic: Problem Solving Techniques  We will learn 1. 2. Problem Statement. Algorithm Types, Example Flowchart  Symbols, Examples.  1.
5. 5. Problem Solving Techniques
6. 6. Problem Statement: Problem Statement help diagnose the situation so that your focus is on the problem, helpful tools at this stage include Algorithms and flowcharts for identifying the expected steps of a process. Therefore to solve any problem,     Collect and analyze information and data Talk with people familiar with the problem If at all possible, view the problem first hand Confirm all findings
7. 7. Algorithm: The algorithm is part of the blueprint or plan for the computer program, an algorithm is: “An effective procedure for solving a class of problems in a finite number of steps.” Every algorithm should have the following 5 characteristic feature: 1. 2. 3. 4. 5. Input Output Definiteness Effectiveness Termination
8. 8. Algorithm (Contd…):  1) 2) 3) 4) 5) 6) To find largest of three numbers Start Read 3 numbers: num1, num2, num3 if num1 > num2 then go to step 5 if num2 > num3 then print num2 is largest else print num3 is largest goto step 6 if num1 > num3 then print num1 is largest else print num3 is largest end.
9. 9. Algorithm (Contd…): Example: One of the simplest algorithms is to find the largest number in an (unsorted) list of numbers. High-level description: 1) 2) 3) Assume the first item is largest. Look at each of the remaining items in the list and if it is larger than the largest item so far, make a note of it. The last noted item is the largest in the list when the process is complete.
10. 10. Algorithm (Contd…): Formal description: Written in prose but much closer to the high-level language of a computer program, the following is the more formal coding of the algorithm in pseudo code (find the largest number in an (unsorted) list of numbers) Algorithm LargestNumber Input: A non-empty list of numbers L. Output: The largest number in the list L. 1) 2) 3) 4) largest ← L0 for each item in the list L, do if the item > largest, then largest ← the item return largest
11. 11. Flowchart: What is a Flowchart?    The flowchart is a means of visually presenting the flow of control through an information processing systems, the operations performed within the system and the sequence in which they are performed. It is a graphic representation of how a process works, showing, at a minimum, the sequence of steps. Flowcharts are generally drawn in the early stages of formulating computer solutions.
12. 12. Flowchart (Contd…): Guideline for drawing a flowchart: Flowcharts are usually drawn using some standard symbols; Some standard symbols, which are frequently required for flowcharting many computer programs are shown below,-
13. 13. Flowchart (Contd…): A set of useful standard Flowchart symbols:     Rounded box use it to represent an event which occurs automatically. Rectangle or box use it to represent an event which is controlled within the process. Typically this will be a step or action which is taken. Diamond use it to represent a decision point in the process. Circle use it to represent a point at which the flowchart connects with another process.
14. 14. ADVANTAGES OF USING FLOWCHARTS:     Communication: Flowcharts are better way of communicating the logic of a system Effective analysis: Problem can be analyzed in more effective way. Proper documentation: Flowcharts serve as a good program documentation Efficient Coding: Flowcharts act as a guide or blueprint during the systems analysis and program development phase.
15. 15. ADVANTAGES OF USING FLOWCHARTS (Contd…):  Proper Debugging: Flowchart helps in debugging process.  Efficient Program Maintenance: The maintenance of operating program becomes easy with the help of flowchart.
16. 16. Flow chart of the while loop :
17. 17. Flow chart of the for loop:
18. 18. The flow chart of the if statement:
19. 19. The flow chart of the if…else statement:
20. 20. The flow chart of the switch statement:
21. 21. Flowchart for finding the sum of first five natural numbers ( i.e. 1,2,3,4,5):
22. 22. Flowchart (Example): Flowchart to find the sum of first 50 natural numbers.
23. 23. Flow Chart to find largest of two numbers: Start Read A, B Yes Is A > B No Print B Print A End
24. 24. Flowchart to find the largest of three numbers A,B, and C: NO
25. 25. LIMITATIONS OF USING FLOWCHARTS:  Complex logic: Sometimes, the program logic is quite complicated. In that case, flowchart becomes complex and clumsy.  Alterations and Modifications: If alterations are required the flowchart may require re-drawing completely.  Reproduction: As the flowchart symbols cannot be typed, reproduction of flowchart becomes a problem.
26. 26. Flowchart (Exercise): 1. Draw a flowchart to depict all steps that you do reach your college. 2. Draw Flowchart for Linear search.