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1. 1. MTS 3013 STRUCTURED PROGRAMMING INTRODUCTION
3. 3. Introduction  A computer is an electronic device capable of performing commands given by human.  Program – Are sequences of instructions and decisions that the computer carries out to achieve a task  Programmer – person responsible in writing a program
4. 4. Defining Control Structures  All computer programs are written using one or more of three basic structures:  Sequence  Repetition  Selection  These are called control structures or logic structures because they control the flow of a program’s logic.
5. 5. The sequence structure  You use it each time you follow a set of directions, in order, from beginning to end.  Example – a cookie recipe – you need to follow each recipe instruction in order, beginning with the first instruction and ending the last
6. 6.  Example – a robot named Didi. Didi can understand only a specific number of instructions / commands : walk, turn, sit  Walk – takes one complete step forward  Turn – turns 180 degree  Sit – sits down  Assume that Didi is facing a chair that is two steps away from him.  Write the instructions using only commands that Didi understands, that direct Didi to sit in the chair.
7. 7. 1. Walk 2. Walk 3. Turn 4. Sit 2 steps algorithm A set of step-by-step instructions that accomplish a task
8. 8. The repetition structure  Example – shampoo bottles typically include repetition structure in the directions for washing your hair. Those direction usually tell you to repeat the “apply shampoo to hair”, “lather”, and “rinse” steps until your hair is clean.  Repetition structure referred to as loop, directs the computer to repeat one or more instructions until some condition is met, at which time the computer should stop repeating the instructions.
9. 9.  Example : Didi is facing a chair that is 50 steps away from him. Write the algorithm that directs Didi to sit in the chair.  Extra command : repeat x times  Solution:  Write “walk” instruction 50 times  Use the “repeat 50 times.” 1. repeat 50 times: walk 2. turn 3. sit
10. 10. The selection structure  Also called decision structure  Makes a decision, and then takes appropriate action based on that decision  Example: you drive your car and approach an intersection, whether you need to stop or proceed.
11. 11. Example  Example: Didi is holding either a red or yellow balloon and that he is facing two boxes. One of the box is colored yellow and the other is colored red. The two boxes are located 20 steps away from Didi. Your task is have Didi to drop the balloon into the appropriate box. The yellow balloon belongs to the yellow box and the red balloon belongs to the red box. After Didi drops the balloon you should return him to the original position.  You may add additional instructions to Didi’s instruction set
12. 12. The algorithm 1. repeat 20 times: walk 2. if the balloon is red, do this: drop the balloon in the red box otherwise drop the balloon in the yellow box 3. turn 4. repeat 20 times walk 5. turn
13. 13.  Calculate the bonus by multiplying the salary 1%  Calculate the bonus by multiplying the salary 2%  If the years employed are greater than or equal to 5, do this:  If the years employed are less than 5, do this:  Otherwise, do this:  Print the bonus  Read the salary and years employed  Repeat for each employee:
14. 14. Exercise  Assume a company pays an annual bonus to its employees. The bonus is based on the number of years the employee has been with the company. Employees working at the company for less than 5 years receive a 1% bonus, all others receive a 2% bonus. Write an algorithm that prints each employee’s bonus. Use only the instructions given:
16. 16. Problem Solving  Problem solving involves:  Analysis  Algorithm or pseudo code or flow chart or combination of them.
17. 17. Problems Analysis  Identify problems:  Input  Output  Process INPUT PROCESS OUTPUT
18. 18. Problem  Write a program obtain average of 3 numbers given by a user. Display the 3 numbers and the average of the numbers.
19. 19. Problems Analysis  Input : 3 numbers  Process : 1. Add 3 numbers 2. Divide sum of the numbers by 3  Output : Print 3 numbers & average
20. 20. Algorithm  Algorithm  Any computing problem can be done by executing a series of actions in a specific order.  A procedure for solving a problem in terms of the actions to be executed and the order in which these actions are to be executed is called an algorithm.  Is a logical solution that is inline with our daily language or mother tongue language.
21. 21. Algorithm Start 1. Set sum = 0 and average = 0 2. Read 3 numbers: nom1, nom2, nom3 3. Add 3 numbers 4. Calculate the average, average = (sum)/3 5. Print 3 numbers(nom1, nom2, nom3) and the average End
22. 22. Pseudo code  Pseudo code  Is an artificial and informal language  Usually it is use English language  Quite similar to programming language  The purpose of pseudo code is to make humans who do not understand computer programming can easily understand the flow of the problem solving.
23. 23. Pseudo code START SET sum = 0, average = 0 INPUT nom1, nom2, nom3 sum = nom1 + nom2 + nom3 average = sum / 3 PRINT nom1, nom2, nom3 PRINT average END
24. 24. Flow Chart  Flow Chart  It is represents by using geometry shapes with connected line  Use a standard symbol
25. 25. Flow Chart TERMINAL Indicates the beginning or end of an algorithm PROCESS Indicates an input computational or data manipulation. INPUT / OUTPUT Indicates an input or output operation
26. 26. Flow Chart DECISION Indicates a decision point in the algorithm CONNECTOR Indicates an entry to or exit from another part of the flowchart FLOW LINES Used to connect the flowchart symbols and indicate the logic flow LOOP Indicates the initial, final and increment values of a loop
27. 27. Example of a flow chart START END sum = 0, average = 0 Input nom1,nom2, nom3 sum = nom1 + nom2 + nom3 average = sum / 3 print nom1,nom2, nom3 print average
28. 28. Exercise  Write an algorithm and a flow chart to calculate and display a volume of a sphere. Volume = 4/3 x pi x radius x radius , where pi = 3.41
29. 29. Solution  Analyze the problem  Input :  Process :  Output : radius Calculate volume of a sphere Volume = 4/3 x pi x radius x radius print volume of a sphere
30. 30. Solution (algorithm) Start 1. Input radius 2. Calculate volume of a sphere Volume = 4/3 x pi x radius x radius 3. print volume of a sphere End
31. 31. Solution (Flow Chart) START END pi = 3.41 Input radius Volume = 4/3 x pi x radius x radius Print volume
32. 32. Control Structures Flow Chart  3 types of control structures:  Sequence structure  Selection structure  If  If… else  Repetition structure  For  While  Do… while
33. 33. Flow Chart for Selection Structure 1 Pseudo code if condition statement 1 Condition / Boolean operator Statement 1 (inside if structure) True False Example Pseudo code if student’s grade is greater than or equal to 60 Print “Passed”
34. 34. Flow Chart for Selection Structure 2 Condition / Boolean operator true false Statement 2 Statement 2 Pseudo code if condition statement 1 Else statement 2 Example Pseudo code if student’s grade is greater than or equal to 60 Print “Passed” Else Print “Failed”
35. 35. Flow Chart for Repetition Structure Condition / Boolean operator Statement 1 (inside if structure) True False Example Pseudo code While there are more items on the shopping list Purchase next item and cross it off my list
36. 36. Module Structure  Used for a big and complex problem  Divide the problem into smaller problem – sub module  To simplify a problem solving Module structure Pseudo code Main module Call sub module End of main module Sub module name Statements End of sub module Main module Sub module 1 Sub module 2
37. 37. TQ