Ds02 flow chart and pseudo code
- 1. Flow Chart and Pseudo Code © Dr. Jyoti Lakhani
- 2. The American National Standards Institute (ANSI) set standards for flowcharts and their symbols in the 1960s. The International Organization for Standardization (ISO) adopted the ANSI symbols in 1970. The current standard, ISO 5807, was revised in 1985. Generally, flowcharts flow from top to bottom and left to right. © Dr. Jyoti Lakhani
- 3. What is a Flowchart? A flowchart is a graphical representations of steps of an Algorithm and programming logic Flowchart Symbols Terminator Process The terminator symbol represents the starting or ending point of the system. A box indicates some particular operation. © Dr. Jyoti Lakhani
- 4. This represents a printout, such as a document or a report. Document Decision A diamond represents a decision or branching point. Lines coming out from the diamond indicates different possible situations, leading to different sub-processes. Data It represents information entering or leaving the system. An input might be an order from a customer. Output can be a product to be delivered. Lines represent the flow of the sequence and direction of a process. Flow © Dr. Jyoti Lakhani
- 5. On-Page Reference This symbol would contain a letter inside. It indicates that the flow continues on a matching symbol containing the same letter somewhere else on the same page. This symbol would contain a letter inside. It indicates that the flow continues on a matching symbol containing the same letter somewhere else on a different page. Off-Page Reference Identifies a delay or a bottleneck. Delay or Bottleneck © Dr. Jyoti Lakhani
- 6. Annotation Indicating additional information about a step in the program. Represented as an open rectangle with a dashed or solid line connecting it to the corresponding symbol in the flowchart Shows named process which is defined elsewhere. Represented as a rectangle with double-struck vertical edges Predefined Process Data File or Database Single documents Multiple documents © Dr. Jyoti Lakhani
- 7. Manual operation Manual input Preparation or Initialization © Dr. Jyoti Lakhani
- 8. © Dr. Jyoti Lakhani
- 9. Calculate Profit and Loss © Dr. Jyoti Lakhani
- 10. Draw a flowchart to input two numbers from user and display the largest of two numbers © Dr. Jyoti Lakhani
- 11. http://flowgorithm.org/download/index.htm Download, Install and Practice © Dr. Jyoti Lakhani
- 12. © Dr. Jyoti Lakhani An example of Algorithm Algorithm to add two numeric values 1. Declare two variables n1 and n2 2. Read values in n1 and n2 3. Declare one more variable sum 4. Add n1 and n2 and assign result in sum 5. Print sum General English
- 13. Flow Chart Implementation Algorithm to add two numeric values Start End Input n1 Input n2 Print Sum Sum = n1 + n2 © Dr. Jyoti Lakhani
- 14. Algorithm Name: Add_Numbers ( n1, n2) Input: Two integers n1 and n2 Output: sum of n1 and n2 Start 1. sum <- n1 + n2 2. Print sum End Pseudo Code Implementation Algorithm to add two numeric values © Dr. Jyoti Lakhani
- 15. Pseudo code is a simple way of writing programming code in English Pseudo code is simply an implementation of an algorithm in the form of annotations and informative text written in plain English. Pseudo code is not actual programming language It has no syntax like any of the programming language and thus can’t be compiled or interpreted by the computer. Algorithms will often be expressed in pseudo code WHY? WHAT? A mixture of code and English “While understanding pseudo code is usually not difficult, writing it can be a challenge” © Dr. Jyoti Lakhani
- 16. Why use pseudo code at all? If we write an algorithm in English, the description may be at so high a level that it is difficult to analyze the algorithm and to transform it into code. If instead we write the algorithm in code, we have invested a lot of time in determining the details of an algorithm we may not choose to implement? The GOAL of writing pseudo code, then, is to provide a high-level description of an algorithm which facilitates analysis and eventual coding but at the same time suppresses many of the details that vanish with asymptotic notation © Dr. Jyoti Lakhani
- 17. Why use pseudo code at all? It allows the designer to focus on the logic of the algorithm without being distracted by details of language syntax. It describe the entire logic of the algorithm so that implementation becomes a rote mechanical task of translating line by line into source code. © Dr. Jyoti Lakhani
- 18. Here are a few general guidelines for checking your pseudo code: -Naomi Nishimura 1. Mimic good code and good English: It is still important that variable names be mnemonic, comments be included where useful, and English phrases be comprehensible (full sentences are usually not necessary). 2. Ignore unnecessary details: you shouldn’t obsess about syntax at all 3. Arrange the sequence of tasks and write the pseudo code accordingly 4. Aim of the algorithm: Start with the statement of a pseudo code which establishes the main goal or the aim. Example: This program will allow the user to check the number whether it's even or odd. © Dr. Jyoti Lakhani
- 19. 5. Proper Indentation: The way the if-else, for, while loops are indented in a program, indent the statements likewise, as it helps to comprehend the decision control and execution mechanism. They also improve the readability to a great extent. Example: if "1" print response "I am case 1" if "2" print response "I am case 2". Example: if "1“ print response "I am case 1“ if "2“ print response "I am case 2" © Dr. Jyoti Lakhani
- 20. 5. Don’t be labor the obvious: In many cases, the type of a variable is clear from context; it is often unnecessary to make it explicit. 6. Take advantage of programming short-hands: Using if-then-else or looping structures is more concise than writing out the equivalent in English; Using parameters in specifying procedures is concise, clear, and accurate, and hence should not be omitted from pseudo code. 7. Use appropriate naming conventions The human tendency follows the approach to follow what we see. If a programmer goes through a pseudo code, his approach will be the same as per it, so the naming must be simple and distinct. © Dr. Jyoti Lakhani
- 21. 8. Use appropriate Naming Convention: such as Camel Case for methods, upper case for constants and lower case for variables. 9. Elaborate everything which is going to happen in the actual code: Don’t make the pseudo code abstract 10. Use standard programming structures such as ‘if-then’, ‘for’, ‘while’, ‘cases’ the way we use it in programming 11. Check whether all the sections of a pseudo code is complete, finite and clear to understand and comprehend 12. Don’t write the pseudo code in a complete programmatic manner: It is necessary to be simple to understand even for a layman or client, hence don’t incorporate too many technical terms. © Dr. Jyoti Lakhani
- 22. Advantages of Pseudo code 1. Improves the readability of any approach. It’s one of the best approaches to start implementation of an algorithm 2. Acts as a bridge between the program and the algorithm or flowchart 3. Also works as a rough documentation, so the program of one developer can be understood easily when a pseudo code is written out. In industries, the approach of documentation is essential. And that’s where a pseudo-code proves vital 4. The main goal of a pseudo code is to explain what exactly each line of a program should do, hence making the code construction phase easier for the programmer © Dr. Jyoti Lakhani
- 23. No broad standard for pseudo code syntax exists, as a program in pseudocode is not an executable program, however certain limited standards exist Pseudo code resembles skeleton programs which can be compiled without errors. Flowcharts, drakon-charts and Unified Modelling Language (UML) charts can be thought of as a graphical alternative to pseudo code, but are more spacious on paper. Languages such as HAGGIS bridge the gap between pseudo code and code written in programming languages. - Wiki © Dr. Jyoti Lakhani
- 24. Type of operation Symbol Example Assignment ← or := c ← 2πr, c := 2πr Comparison =, ≠, <, >, ≤, ≥ Arithmetic +, −, ×, /, mod Floor/ceiling ⌊, ⌋, ⌈, ⌉ a ← ⌊b⌋ + ⌈c⌉ Logical and, or Sums, products Σ Π h ← Σa∈A 1/a Some Conventions to write Pseudo Code - Wiki © Dr. Jyoti Lakhani
- 25. Common Action Keywords: Input: READ OBTAIN GET Output: PRINT DISPLAY SHOW Compute: COMPUTE CALCULATE DETERMINE Initialize: SET INIT Add one: INCREMENT BUMP Action Words © Dr. Jyoti Lakhani
- 26. IF-THEN-ELSE The general form is: IF condition THEN sequence 1 ELSE sequence 2 ENDIF IF HoursWorked > NormalMax THEN Display overtime message ELSE Display regular time message ENDIF Example: © Dr. Jyoti Lakhani
- 27. WHILE The general form is: WHILE condition sequence ENDWHILE The loop is entered only if the condition is true. WHILE Population < LimitCompute Population as Population + Births – Deaths ENDWHILE © Dr. Jyoti Lakhani
- 28. CASE The general form is: CASE expression OF condition 1 : sequence 1 condition 2 : sequence 2 ... condition n : sequence n OTHERS: default sequence ENDCASE CASE grade OF A : points = 4 B : points = 3 C : points = 2 D : points = 1 OTHERS : points = 5 ENDCASE © Dr. Jyoti Lakhani
- 29. FOR The general form is: FOR iteration bounds sequence ENDFOR Example: FOR each month of the year (good) FOR month = 1 to 12 (ok) FOR each employee in the list (good) FOR empno = 1 to listsize (ok) © Dr. Jyoti Lakhani
- 30. REPEAT-UNTIL The general form is: REPEAT sequence UNTIL condition NESTED CONSTRUCTS Example: SET total to zero REPEAT READ Temperature IF Temperature > Freezing THEN INCREMENT total END IF UNTIL Temperature < zero © Dr. Jyoti Lakhani
- 31. INVOKING SUBPROCEDURES Use the CALL keyword. For example: CALL AvgAge with StudentAges CALL Swap (CurrentItem, TargetItem) CALL getBalance RETURNING aBalance BEGIN statements EXCEPTION WHEN exception type statements to handle exception WHEN another exception type statements to handle exception END EXCEPTION HANDLING © Dr. Jyoti Lakhani
- 32. © Dr. Jyoti Lakhani