![Pseudocode
• read/get – indicates a user will be inputting something
• display/print/show – indicates that an output will appear on the screen
• SET, INIT: To initialize values
• Expressions
• ←Assignment (like = inC)
• = Equality testing (like = = inC)
• n2 superscripts and other mathematical formatting allowed
• Method call
• var.method (arg [, arg…])
• Return value
• return expression](https://image.slidesharecdn.com/1-240315185410-1b560e96/85/Algorithms-for-c-nit-jamshedpur-first-year-16-320.jpg)
Algorithms for c nit jamshedpur first year
- 1. CS1101 Introduction toComputer Programming and Data Structures Dr. B Ramachandra Reddy
- 2. Outline • Algorithm • Flow Charts • Pseudo Code
- 3. Program Planning To write a correct program, a programmer must write each and every instruction in the correct sequence Logic (instruction sequence) of a program can be very complex Hence, programs must be planned before they are written to ensure program instructions are: Appropriate for the problem In the correct sequence
- 4. Algorithm Refers to the logic of a program and a step-by-step description of how to arrive at the solution of a given problem. In order to qualify as an algorithm, a sequence of instructions must have following characteristics: Each and every instruction should be precise and unambiguous Each instruction should be such that it can be performed in a finite time One or more instructions should not be repeated infinitely. This ensures that the algorithm will ultimately terminate After performing the instructions, that is after the algorithm terminates, the desired results must be obtained
- 5. SampleAlgorithm (Example 1) • There are 50 students in a class who appeared in their final examination. Their mark sheets have been given to you. • The division column of the mark sheet contains the division (FIRST, SECOND, THIRD or FAIL) obtained by the student. • Write an algorithm to calculate and print the total number of students who passed in FIRST division.
- 6. SampleAlgorithm (Example 1) Step 1: Initialize Total_First_Division and Total_Marksheets_Checked to zero. Step 2: Take the mark sheet of the next student. Step 3: Check the division column of the mark sheet to see if it is FIRST, if no, go to Step 5. Step 4: Add 1 to Total_First_Division. Step 5: Add 1 to Total_Marksheets_Checked. Step 6: Is Total_Marksheets_Checked = 50, if no, go to Step 2. Step 7: Print Total_First_Division. Step 8: Stop.
- 7. Representation ofAlgorithms As flowcharts As pseudocodes
- 8. Flowchart Flowchart is a pictorial representation of an algorithm Uses symbols (boxes of different shapes) that have standardized meanings to denote different types of instructions Actual instructions are written within the boxes Boxes are connected by solid lines having arrow marks to indicate the exact sequence in which the instructions are to be executed Process of drawing a flowchart for an algorithm is called flowcharting
- 10. Examples of Decision Symbol Is I = 10? No Yes (a) A two-way branch decision. (b) A three-way branch decision. A > B A = B A < B Compare A & B
- 11. Examples of Decision Symbol I = ? (c) A multiple-way branch decision. = 0 = 1 = 2 = 3 = 4 = 5 = Other
- 12. Sample Flowchart
- 13. Sample Flowchart
- 14. Pseudocode A program planning tool where program logic is written in an ordinary natural language using a structure that resembles computer instructions “ Pseudo” means imitation or false and “ Code” refers to the instructions written in a programming language. Hence, pseudocode is an imitation of actual computer instructions Because it emphasizes the design of the program, pseudocode is also called Program Design Language (PDL)
- 15. Basic Logic (Control) Structures • Any program logic can be expressed by using only following three simple logic structures: 1. Sequence logic, 2. Selection logic, and 3. Iteration (or looping) logic • Programs structured by using only these three logic structures are called structured programs, and the technique of writing such programs is known as structured programming
- 16. Pseudocode • read/get – indicates a user will be inputting something • display/print/show – indicates that an output will appear on the screen • SET, INIT: To initialize values • Expressions • ←Assignment (like = inC) • = Equality testing (like = = inC) • n2 superscripts and other mathematical formatting allowed • Method call • var.method (arg [, arg…]) • Return value • return expression
- 17. SequenceLogic Process 1 (b) Pseudocode Process 2 Process 1 Process 2 (a) Flowchart
- 18. Selection Logic • Also known as decision logic, it is used for making decisions • Three popularly used selection logic structures are 1. IF…THEN…ELSE 2. IF…THEN 3. CASE
- 19. Selection Logic (IF…THEN…ELSE Structure) THEN ELSE Process 1 Process 2 IF Condition ENDIF (b) Pseudocode THEN Process 1 ELSE Process 2 Yes No (a) Flowchart IF (condition)
- 20. Selection Logic (IF…THEN Structure) (b) Pseudocode THEN ENDIF IF Condition Process 1 THEN Process 1 Yes No (a) Flowchart IF (condition)
- 21. Selection Logic (CASE Structure) (b) Pseudocode CASE Type Case Type 1: Case Type 2: Process 1 Process 2 ENDCASE Case Type n: Process n Type 1 Type n Process 2 Process 1 Process n Yes Yes Yes No Type 2 No No (a) Flowchart
- 22. Iteration (or Looping) Logic Used to produce loops in program logic when one or more instructions may be executed several times depending on some conditions Two popularly used iteration logic structures are 1. DO…WHILE 2. REPEAT…UNTIL
- 23. Iteration (or Looping) Logic (DO…WHILE Structure) (b) Pseudocode DO WHILE Condition Process 1 Process n ENDDO Process 1 False (a) Flowchart Process n True Condition? Block
- 24. Iteration (or Looping) Logic (REPEAT…UNTIL Structure) (b) Pseudocode REPEAT Process 1 Process n UNTIL Condition Process 1 Process n True (a) Flowchart False Condition?
- 25. SampleAlgorithm
- 26. SampleAlgorithm
- 28. Flowchart Pseudocode Start/End Begin/End Input/output Read: read x,y Print: Print y Process Computation: X<-y+6 Decision If/if-lse/case/while/ do-while/for Connector Not Applicable Predefined Process Not Applicable FlowchartVs Pseudo code
- 29. FlowchartVs Pseudo code • Flowchart Advantages • Standard • Visual • Flowchart Disadvantages • Hard to modify • Structured design elements not implemented • Special software required • Pseudocode Advantages • Easily modified • Implements structured concepts • Done easy on Word Processor • Pseudocode Disadvantages • Not Visual • Not accepted standard, varies from company to company
- 30. Assignments • Write a pseudo code and flowchart to find the given number is prime or not? • Write a pseudo code and flowchart to generate the Fibonacci series upto n numbers. • Write a pseudo code and flowchart to check the given number is palindrome or not?