Presentation on theme: "Introduction to Programming"— Presentation transcript:
1 Introduction to Programming AlgorithmsAndreas Savva
2 What is an algorithm?An Algorithm is a detailed sequence of simple steps that are needed to solve a problem.It is a step-by-step solution to a problem.
3 Mathematical ExampleProblem: What is the value of x in the following equation?5x – 10 = 30Algorithm (Solution):Step 1: 5x =Step 2: 5x = 40Step 3: x = 40/5Step 4: x = 8
4 Making a cake Step 1: Preheat oven to 200 degrees. Step 2: Mix the eggs with the sugar.Step 3: Add the butter, flour, and the rest of the ingredients.Step 4: Stir for 5 minutes.Step 5: Put the mixture into a baking pan and cook it in a 175 degrees for 40 minutes.Step 6: Keep it in the pan for 15 minutes to cool down.Step 7: Serve with vanilla ice-cream.
5 Algorithms The Problem: How will the robot go to the file folder? Step 1: Move 3 squares and turn right.Step 2: Move 1 square and turn left.Step 3: Move 2 squares and turn left.Step 4: Move 2 squares and turn right.etc.The Problem: How will the robot go to the file folder?
6 Representation of Algorithms Verbal representationPseudo-codeFlowchart
7 Verbal representation of Algorithms Example: Write an algorithm to read and calculate the average of three numbers.Algorithm:Step 1: Ask for the first number.Step 2: Ask for the second number.Step 3: Ask for the third number.Step 4: Add the three numbers to find their sum.Step 5: Divide the sum by 3.Step 6: Display the result.
8 Flowcharts - graphical representation of an algorithm Start – FinishInput – OutputProcessingSub-programs (Separate flowchart)Choice Statements (Question, Decision)CommentsFlow
9 Flowchart G R Sum a Average b c Start Read a Read b Read c Sum a + b + cAverage Sum / 3Display AverageFinish
10 StructuresFor the solution of a problem we use three basic structures:Sequential structureConditional structureRepetitive structure
11 Example 2Write an algorithm to read two numbers and display the appropriate message if the two numbers are equal or not.Read a.Read b.If a = b then display that the two numbers are equal.Else display that the two numbers are NOT equal.
12 Conditional Structure Start Read a Read b FALSE a = b ? TRUE Display: ”The two numbersare not equal”Display:”The two numbersare equal”Finish
13 Example 3Write an algorithm to read two numbers a and b and find the sum of all the numbers between a and b inclusive. i.e.a = 3, b = 7, Sum = = 25a = 1, b = 100, Sum = … = 5,050Read a, bSum 0Counter aIf Counter > b then Goto 8Sum Sum + CounterCounter Counter + 1Goto 4Display Sum
14 Repetitive Structure Start Read a, b Sum 0 i a i is the Counter i > b ?TRUEFALSESum Sum + ii i + 1Display SumFinish
15 Exercises Design a flowchart for the following problems: Calculate the weekly salary of an employee, when the employee-name, working-hours, and rate-per-hour are given. If the working-hours exceed 40, the rate-per-hour is double than the normal hour.Given 4 numbers X1, X2, X3, and X4, find and display the smaller one.Given two numbers A and B. Calculate and display the remainder of their division B:A. (Hind: Keep subtracting A from B until you find a smaller number than A. i.e. for the division 20:6 it will be 20 – 6 = 14; 14 – 6 = 8; 8 – 6 = 2; so Remainder = 2).