Algorithms and Flowcharts

•A typical programming task can be divided into two phases:
•Problem solving phase
•produce an ordered sequence of steps that describe solution of problem
•this sequence of steps is called an algorithm
•Implementation phase
•implement the program in some programming language
Example 1:Write an algorithm to determine a student’s final grade and indicate whether it is passing or failing. The final grade is calculated as the average of four marks.
Detailed Algorithm
•Step 1: Input M1,M2,M3,M4
Step 3: if (GRADE < 50) then
Print “FAIL”
else
Print “PASS”
Endif
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Flowchart:
A graphical representation of the sequence of operations in an information system or program. Information system flowcharts show how data flows from source documents through the computer to final distribution to users. Program flowcharts show the sequence of instructions in a single program or subroutine. Different symbols are used to draw each type of flowchart.
A Flowchart
•shows logic of an algorithm
•emphasizes individual steps and their interconnections
•e.g. control flow from one action to the next
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Flowchart Symbols Basic:
Name Symbol Use in Flowchart
Oval Denotes the beginning or end of the program
Parallelogram Denotes an input operation
Rectangle Denotes an output operation
Diamond Denotes a decision (or branch) to be made. The
program should continue along one of two routes. (e.g. IF/THEN/ELSE)
Hybrid Denotes a process to be carried out e.g. addition,
subtraction, division etc. Flow line
Flow line Denotes the direction of logic flow in the program
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