Introduction to Flowcharting

Objective A program can be divided into 3 parts: Input data Processing data – Calculation, etc. Output information/results Calculation/ Processing Input Output

Arrows From Top to Bottom & from Left to Right Make turn Join together NOTE: Lines/Arrows must always be horizontal or vertical and never cross to avoid confusion

What is a Flowchart? START Display message “How many hours did you work?” Read hours Display message “How much do you get paid per hour?” Read payRate Multiply hours by payRate. Store result in grossPay. Display grossPay END A flowchart is a diagram that depicts the “flow” of a program. A diagram made up of symbols of various shapes connected by arrows. Those symbols indicate either actions to be taken or decisions to be made. It helps us planning & programming. The figure shown here is a flowchart for a pay-calculating program. NOTE: Like IPO charts, there should be nothing programming language specific, just use descriptive words, e.g. “Read” or “Display”

Four Flowchart Structures Sequence (Today) Decision Case Repetition

Sequence Structure A series of actions are performed in sequence The pay-calculating example was a sequence flowchart.

Basic Flowchart Symbols Rounded Rectangle START Display message “How many hours did you work?” Read hours Notice there are three types of symbols in this flowchart: rounded rectangles parallelograms rectangles Each symbol represents a different type of operation. Display message “How much do you get paid per hour?” Parallelogram Read payRate Multiply hours by payRate. Store result in grossPay. Rectangle Display grossPay Rounded Rectangle END

Terminals: Rounded Rectangles START Display message “How many hours did you work?” Terminals represented by rounded rectangles indicate a starting or ending point Only 1 of each allowed! Read hours Display message “How much do you get paid per hour?” Read payRate Multiply hours by payRate. Store result in grossPay. START Display grossPay END Terminal END

I/O Operations: Parallelograms START Display message “How many hours did you work?” Input/Output Operations represented by parallelograms indicate an input or output operation Read hours Display message “How much do you get paid per hour?” Input/Output Operation Read payRate Multiply hours by payRate. Store result in grossPay. Display message “How many hours did you work?” Read hours Display grossPay END

Processing: Rectangles START Display message “How many hours did you work?” Processes represented by rectangles indicates a process such as a mathematical computation or variable assignment (not definition) Read hours Display message “How much do you get paid per hour?” Read payRate Calculate grossPay as hours * payRate Multiply hours by payRate. Store result in grossPay. Process Multiply hours by payRate. Store result in grossPay. Set name to “Fred” Display grossPay END

Stepping Through the Flowchart START Display message “How many hours did you work?” In the next seven slides we will step through each symbol in the flowchart. We will show the program output and the contents of the variables. Read hours Display message “How much do you get paid per hour?” Read payRate Multiply hours by payRate. Store result in grossPay. Variable Contents: hours: ? payRate: ? grossPay: ? Display grossPay END

Stepping Through the Flowchart START Step 1: An Output Operation Display message “How many hours did you work?” Read hours Screen Output How many hours did you work? Display message “How much do you get paid per hour?” Read payRate Multiply hours by payRate. Store result in grossPay. Variable Contents: hours: ? payRate: ? grossPay: ? Display grossPay END

Stepping Through the Flowchart START Display message “How many hours did you work?” Read hours Step 2: An Input Operation (User types 40) How many hours did you work? 40 Display message “How much do you get paid per hour?” Read payRate Multiply hours by payRate. Store result in grossPay. Variable Contents: hours: 40 payRate: ? grossPay: ? The value 40 is stored in hours. Display grossPay END

Stepping Through the Flowchart START Display message “How many hours did you work?” Read hours Screen Output How much do you get paid per hour? Display message “How much do you get paid per hour?” Step 3: An Output Operation Read payRate Multiply hours by payRate. Store result in grossPay. Variable Contents: hours: 40 payRate: ? grossPay: ? Display grossPay END

Stepping Through the Flowchart START Display message “How many hours did you work?” Read hours How much do you get paid per hour? 20 Display message “How much do you get paid per hour?” Read payRate Step 4: Input Operation (User types 20) Multiply hours by payRate. Store result in grossPay. Variable Contents: hours: 40 payRate: 20 grossPay: ? Display grossPay The value 20 is stored in payRate. END

Stepping Through the Flowchart START Display message “How many hours did you work?” Read hours How much do you get paid per hour? 20 Display message “How much do you get paid per hour?” Step 5: The product of hours times payRate is stored in grossPay Read payRate Multiply hours by payRate. Store result in grossPay. Variable Contents: hours: 40 payRate: 20 grossPay: 800 Display grossPay The value 800 is stored in grossPay. END

Stepping Through the Flowchart START Display message “How many hours did you work?” Read hours Screen Output Your gross pay is 800 Display message “How much do you get paid per hour?” Read payRate Multiply hours by payRate. Store result in grossPay. Variable Contents: hours: 40 payRate: 20 grossPay: 800 Display grossPay Step 6: An Output Operation END

Connectors Sometimes a flowchart will not fit on one page. A connector (represented by a small circle) allows you to connect two flowchart segments. A

Connectors The “A” connector indicates that the second flowchart segment begins where the first segment ends. If you needed multiple connectors, you would use different letters for each, e.g. “B”, “C” Think of it as a “teleporter” A START END

Review What do each of the following symbols represent? (Answer on next slide)

Review What do each of the following symbols represent? Terminal Input/Output Operation Process

Review Name the four flowchart structures. Sequence Decision Repetition Case (Answer on next slide)