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algorithm
The document defines algorithms and different representations of algorithms such as normal English, flow charts, pseudo code, and programs. It provides examples of different control structures like sequence, selection, and repetition. Key points include: algorithms must be unambiguous, terminate in a finite number of steps, and time, memory, accuracy and generality are qualities of a good algorithm. Pseudo code uses keywords and indentation to represent program logic clearly. Flow charts use standard symbols and avoid intersecting lines to depict a process visually. Control structures determine the order of execution through sequencing, conditional checks, or repeated execution.
algorithm
- 1.
- 2. Definition: • Algorithm isa finite sequence of instructions required for producing the desired result. • It is also defined as “any problem whose solution can be expressed in a list of executable instruction.”
- 3. Characteristics: • The stepsin the algorithm must be unambiguous . • It should be written in sequence. • Ensure that the algorithm will terminate. • It should conclude after a finite number of steps.
- 4. Quality of goodalgorithm: • Time • Memory • Accuracy • Sequence • Generality
- 5. Representation of algorithm: •Normal English -The algorithm is represented in step by step sequential order in normal English. • Flow chart- It is a pictorial representation of an algorithm. • Pseudo code –it is a formal design tool and utilized very well with the rules of structure design and programming.
- 6. Contd.. • Decision table-it is used to helps a lot in designing a specific segment of a design. • Program - it is represented as a program using any high level language.
- 7. Example • Addition oftwo numbers Step1: Start Step2: Read a, b Step3: Add the value of a with b and store the result in c. Step4: Display the value of c Step5: Stop
- 8.
- 9. Definition: • Pseudo meansimitates and code means instruction. • It is formal design tool. • It is also called Program Design Language.
- 10. Keywords • READ,GET • PRINT,DISPLAY •COMPUTE,CALCULATE
- 11. Guidelines for writingPseudo code • Steps should be understandable • Capitalize the keyword. • Indent to show hierarchy. • End multiple line structure etc,.
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- 13. Example READ a,b IF a>b PRINTa is greater ELSE PRINT b is greater ENDIF stop
- 14. Advantage & Disadvantage •It can be easily modified • It can be understood easily • Compare to flowchart it is difficult to understand the program logic.
- 15. Flowcharts • It isthe pictorial representation of the algorithm. • A flow chart, or flow diagram, is a graphical representation of a process or system that details the sequencing of steps required to create output. • A flowchart is a picture of the separate steps of a process in sequential order.
- 16. Flowchart Symbols • Terminalsymbol – It is used to represent the start, end of the program logic. • Input/Output – It is used for input or output. • Process Symbol – It is used to represent the calculations, data movements, initialization operations etc,.
- 17. • Decision Symbol –It is used to denote a decision to be made at that point • Flow lines – It is used to connect the symbols • Connectors – It is used to connect the flow lines.
- 18. Rules for preparing flowcharts •It should be simple. • Standard symbols should be used. • The flow lines should not intersect each others. • In case of complex flowcharts use the connectors symbols.
- 19. • Only oneflow line should enter the process symbol and only one flow line should come out from a process symbol. • Only one flow line used with the terminal symbol. START STOP
- 20. • Only oneflow line should enter the decision symbol and two or three flowlines may leave from the decision symbol.
- 21. Benefits of Flowcharts •Makes Logic Clear • Communication • Effective Analysis • Useful in coding • Useful in Testing etc,.
- 22. Limits of Flowcharts •It is difficult to use flowcharts for large program • Difficult to modify • Cost etc,.
- 23. Program control structures: •Program control structure are defined as the program statements that specifies the order in which statements are executed. • Types: – Sequence control structure – Selection control structure – Repetition control structure
- 24. • The instructionsare computed in sequence i.e. it performs instruction one after another. • It uses top-down approach. Sequence control structure
- 25. Sequence control structure Flowchart Pseudo code Process 1 Process 2 Process nProcess 2 Process n Process 1
- 26.
- 27. SELECTION CONTROL STRUCTURE • Itis used for making decisions. • It allows the program to make a choice from alternative paths. • IF …THEN • IF …THEN… ELSE • CASE etc.,
- 28. IF…THEN Pseudo code Flow chart IFcondition THEN process 1 . . END IF . . If condition NO YES Process 1
- 29. Example Start Read a If a>0 Printa is Positive Stop no yes
- 30. IF…THEN…ELSE Pseudo code Flowchart IFcondition THEN process 1 . . ELSE process 2 . . END IF . . If condition YES NO Process 1 Process 2
- 31. Example Start Read a,b If a>b Printa is Greater Print b is Greater Stop no yes
- 32. CASE structure Pseudo codeFlow chart . . CASE Type Case Type-1: Process 1 Case Type-2: Process 2 . . Case Type-n: Process n . . END CASE Type 1 Type 2 Type 3 Process 1 Process 2 Process 3 no no no yes yes yes
- 33. start stop Read m1,m2,m3 Avg=(m1+m2+m3)/3 If Avg>=60 If Avg>=50 If Avg>=35 Fail Print First Class Print SecondClass Print Third Class Example: Finding the Grade
- 34. Repetition control structure(looping) •It is used to execute some instructions several time based on some condition. • WHILE loop • Do…WHILE loop etc.,
- 35. WHILE Loop Pseudo codeFlow chart WHILE condition . . Body of the loop . . END WHILE Body of The loop condition no yes
- 36.
- 37. DO…WHILE Loop Pseudocode Flowchart DO . . Body of the loop . . WHILE condition . . END WHILE Body of The loop condition no yes
- 38.
- 39. Example: Finding thearea of a circle Algorithm Step1: Start Step2: Read the value of r Step3: Calculate area = 3.14*r*r Step4: Print area Step5: Stop