Flowchart Structure 25th October 2018

Transcription

1 Flowchart Structure 25 th October 2018

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3 Section 1: Basic rules in flowchart Section 2: Translating Pseudocode to Flowchart Algorithm Section3: Examples of Flowchart Section 4: Control structures (Sequence, Selection, Repetition

4 Flowchart - a traditional graphical tool with standardized symbols. Show the sequence of steps in an algorithm. Flowcharts are also called block diagrams, flow diagrams, system charts, procedural charts, run diagrams and logic charts. 1. The flowchart should flow from top to bottom 2. If the chart becomes complex, utilize connecting blocks 3. Avoid intersecting flow lines 4. Use meaningful description in the symbol

5 TYPES of FLOWCHARTS System Outline charts System Flowcharts Run Flowcharts Program Flowcharts NB: Appropriate use of flow symbols are critical in program flowchart than the other three (3)

6 1. Complex- The major disadvantages in using the flowcharts is that when a program is very large, the flowcharts may continue for many pages, making them hard to follow. 2. Costly- Drawing flowcharts are viable only if the problem solving logic is straight forward and not very lengthy. However, if flowcharts are to be drawn for a huge application, the time and cost factor of program development may get out of proportion.

7 3. Difficult to modify- due to symbolic nature, any changes of modifications to a flowcharts usually requires redrawing the entire logic again, and redrawing a complex flowchart is not a simple tasks. 4. No update: usually program are updated regularly. However corresponding update in the flowchart may not take place, especially in the case of large programs. As a result the logic in flowchart may not match with the actual program; causing logical error.

8 Relational Operators Operator Description > Greater than < Less than = Equal to Greater than or equal to Less than or equal to Not equal to

9 Flowcharting Symbols SYMBOL NAME DESCRIPTION TERMINAL Start/Stop Begin/End INITIALIZATION INPUT/OUTPUT PROCESS FLOW LINES DECISION MAKING Defines the starting and ending point of a flowchart. The preparation or initialization of memory space for data processing. The inputting of data for processing, and printing out of processed data. Manipulation of data(assignments and mathematical computations) Defines logical sequence of the program. Its points to the ext symbol to be performed Process conditions using relational operators. Used for trapping and filtering data.

10 Control Structures Application Examples: Flowcharts Sequence So let s say we want to express the following algorithm: Read in a number and print it out.

11 START Every programming has Start point and End point to avoid infinity execution

12 START Read in A Read is the input to be processed during the execution/running

13 START Read in A Print A Print is the Output/results after the processing of A

14 START Read in A Print A END End means the system has to stop running. We have obtained the results

15 Examples: Flowcharts Selection So let s say we want to express the following algorithm: Read in a number, check if it is odd or even.

16 START

17 START Read in A

18 START Read in A Does A/2 give a remainder? Introduction of selection/decision symbol

19 START Read in A Print It s Odd Yes Does A/2 give a remainder?

20 START Read in A Print It s Odd Yes Does A/2 give a remainder? No Print It s Even

21 START Read in A Print It s Odd Yes Does A/2 give a remainder? No Print It s Even END

22 Examples: Flowcharts Iteration So let s say we want to express the following algorithm: We want to wash our hand under a tap until hands are clean.

23 Start Turn on Water Dispense Soap Rub Hands Together YES Hands Clean? NO Wash Hands till Clean (Iteration/loop/while) Rinse Soap Off Turn off Water Dry Hands END

24 Flow chart to explain how to wash your hair Start Wet Hair Set Wash Count To 0 Lather Hair Rinse Hair Add 1 to value of Wash Count Wash Count =2? No Stop Yes

25 Example: 3 Complex

26 PRINT PASS START Input M1,M2,M3,M4 GRADE (M1+M2+M3+M4)/4 N IS GRADE<50 Y PRINT FAIL Pseudocode: Start 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 stop STOP

27 Write an algorithm in pseudocode and draw a flowchart to convert the length in feet to centimeter. Pseudocode: Begin Input the length in feet (Lft); Calculate the length in cm (Lcm) by multiplying LFT with 30; Print length in cm (LCM); End

28 Algorithm Step 1: Input Lft Step 2: Lcm Lft x 30 Step 3: Print Lcm Flowchart START Input Lft Lcm Lft x 30 Print Lcm STOP

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30 Question: With the aid of flowchart diagram, programme your future and career life for the next 7-10years. Write definite procedure and use the following set of rules in the algorithm: Sequence, selection and iterations (optional) where necessary. NB: Consider in the process; 1. National Service 2. Job Market Entry/self-employment 3. Marriage, 4. Expectancy: 1 st Child, 2 nd Child, 3 rd Child nth Child 5. Master Degree (2years) 6. PHD (4years+1year language studies in some countries) 7. Abroad visit/stay (optional)

31 Summary: 1. Pseudocode 2. Flowchart 3. Translating Pseudocode to flowchart 4. Coding unto machine-vb Platform (4) Lab Assignment: Use Visual Basics to Implement Algorithm. Download assignment from Sakai Thank you