LEC 5 [CS 101] Introduction to computer science.pdf
- 1. Modern Academy FOR Computer Science & Management Technology in Maadi Department of Computer Science • Subject: (CS 101) Introduction to Computer Science • Professors: Prof. Mahmoud Gadallah, and Dr. Mohamed Elnabawy • Tutorial and Lab Coordinator: Instructor Teams • CONTACT: ( LMS-MOODLE) & (WhatsApp: 01005586337). E-Mail: [email protected] • COURSE RULES: GRADES/ LATE HW/ ATTENDANCE. CS 101 Dr. Mohamed M. Elnabawy Fall 2025
- 2. General Objective of the Course 1. Define the basic concepts and components of computer system (hardware and software). 2. Describe the computer organization and its different hardware components. 3. Apply the methodologies of problem solving and program development and translate the solution to an algorithm or flow chart. 4. Describe the basic structure of computer networks and the associated hardware.
- 3. Chapter 2: Problem Solving and Program Development
- 5. pseudocode Basic Guidelines for Pseudocode: 1- Do not use language-specific commands in your statements Pseudocode should be universal. So, when creating the task list you would not include commands that are for any specific language like C++, Java, C#. The point of pseudocode is to design a program that can be translated into any language. 2- Write only one task/statement per line Make sure you put only one task on each line. Including too much information on one line can be confusing and increases the possibility of errors. 3- Capitalize Keywords Capitalizing keywords like Read, Write, or Display helps to show when an action is occurring or when a specific command or process will be necessary when coding in your specific language. 4- Indent statements in a loop to better see the flow of your program
- 6. Pseudocode (Cont.) The "structured" part of pseudocode is a notation for representing specific structured programming constructs: 1. SEQUENCE: is a linear progression where one task is performed sequentially after another. 2. SELECTION: ❖ IF-THEN-ELSE: is a decision (selection) in which a choice is made between two alternative courses of action. ❖ CASE: is a multiway branch (decision) based on the value of an expression. CASE is a generalization of IF-THEN-ELSE. 3. REPETITION: ❖ WHILE: is a loop (repetition) with a simple conditional test at its beginning. ❖ REPEAT-UNTIL: is a loop with a simple conditional test at the bottom. ❖ FOR: is a "counting" loop.
- 7. • Sequential control is indicated by writing one action after another, each action on a line by itself, and all actions aligned with the same indent. • The actions are performed in the sequence (top to bottom) that they are written. Example (non-computer) Brush teeth Wash face Comb hair Smile in mirror Example READ height of rectangle READ width of rectangle COMPUTE area as height times width • Sequence Structure Pseudo code
- 8. Common Action Keywords: Input: READ, OBTAIN, GET Output: PRINT, DISPLAY, SHOW Compute: COMPUTE, CALCULATE, DETERMINE Initialize: SET, INIT Add one: INCREMENT, BUMP • Sequence Structure Pseudo code
- 9. IF-THEN-ELSE A binary choice on a given Boolean condition is indicated by using four keywords: IF, THEN, ELSE, and ENDIF. The general form is: IF condition THEN Sequence 1 ELSE Sequence 2 ENDIF • The ELSE keyword and “sequence 2” are optional. • If the condition is true, sequence 1 is performed, otherwise, sequence 2 is performed. • Selection Pseudo code
- 10. Example IF HoursWorked > NormalMax THEN Display overtime message ELSE Display regular-time message ENDIF • Selection Pseudo code
- 11. CASE • A CASE construct indicates a multiway branch based on mutually exclusive conditions. • Four keywords, CASE, OF, OTHERS, and ENDCASE, and conditions are used to indicate the various alternatives. The general form is: CASE expression OF condition 1 : sequence 1 condition 2 : sequence 2 ... condition n : sequence n OTHERS: default sequence ENDCASE • Selection Pseudo code
- 12. • The OTHERS sentence with its default sequence is optional. • Conditions are normally numbers or characters indicating the value of "expression", but they can be English statements or some other notation that specifies the condition under which the given sequence is to be performed. • A certain sequence may be associated with more than one condition. • Selection Pseudo code
- 13. Example: CASE Title OF Mr : Print "Mister" Mrs : Print "Missus" Miss : Print "Miss" Ms : Print "Mizz" Dr : Print "Doctor" ENDCASE • Selection Pseudo code Example: CASE grade OF A : points = 4 B : points = 3 C : points = 2 D : points = 1 F : points = 0 ENDCASE
- 14. WHILE • The WHILE construct is used to specify a loop with a test at the top. • The beginning and ending of the loop are indicated by two keywords WHILE and ENDWHILE. • The general form is: WHILE condition sequence ENDWHILE The loop is entered only if the condition is true. The "sequence" is performed for each iteration. After each iteration, the condition is evaluated and the loop continues as long as the condition is true. • Repetition (Loop) Pseudo code
- 15. Example WHILE Population < Limit Compute Population as Population + Births - Deaths ENDWHILE • Repetition (Loop) Pseudo code
- 16. REPEAT-UNTIL • This loop is similar to the WHILE loop except that the test is performed at the bottom instead of at the top. • Two keywords, REPEAT and UNTIL are used. The general form is: REPEAT sequence UNTIL condition • Repetition (Loop) Pseudo code
- 17. • The "sequence" in this type of loop is always performed at least once, because the test is performed after the sequence is executed. • After each iteration, the condition is evaluated, and the loop repeats if the condition is false. • The loop terminates when the condition becomes true. • Repetition (Loop) Pseudo code
- 18. FOR This loop is a specialized construct for iterating a specific number of times, often called a "counting" loop. Two keywords, FOR and ENDFOR are used. The general form is: FOR iteration bounds sequence ENDFOR In cases where the loop constraints can be related it is best to describe the loop using problem domain vocabulary. • Repetition (Loop) Pseudo code
- 19. Examples
- 20. Develop an algorithm that calculates and prints the area of a trapezoid with two bases of lengths base1 and base2 and height h. Example: 1- The problem: Writing an algorithm to calculate and print the area of a trapezoid Sequence structure
- 21. 2- Reasoning: In this step we describe the following: Formal statement: trapezoid problem Input(s): base1, base2, height Output(s): area Process(es): area = ((base1 + base2) / 2) x height 3- Solution (Design the algorithm): In this step, the solution can be put in the form of a flow chart or an algorithm written in a pseudo code language. Sequence structure
- 22. Start Input base1, base 2, height basesum = base1 + base2 area = (basesum / 2) x height OUTPUT area Stop The Algorithm of the trapezoid problem • The Flow Chart The Flow Chart (Cont.)
- 23. • The Algorithm in pseudo code: START Step 1: INPUT base1 Step 2: INPUT base2 Step 3: INPUT height Step 4: basesum = base1 + base2 Step 5: area = (basesum / 2) x height Step 6: OUTPUT area Step 7: STOP pseudocode
- 24. • Desk checks that this sequence of steps is an algorithm whose execution solves the intended problem. • Try the reasonable values: base1 = 10 base2 = 20 Height = 15 Then basesum = 10 + 20 = 30 and Area = (30/2) x 15 = 225 START Step 1: INPUT base1 Step 2: INPUT base2 Step 3: INPUT height Step 4: basesum = base1 + base2 Step 5: area = (basesum / 2) x height Step 6: OUTPUT area Step 7: STOP 4- Test
- 25. Selection: Is the choice of alternate paths (branches) depending on a possibility that may arise in the logical flow of the algorithm. Pseudo code Flow Chart IF Condition THEN Process 1 ELSE Process 2 ENDIF Cond ition ? YES NO Process 2 Process 1 II- Selection
- 26. Problem Write an algorithm that accepts a number representing either a Fahrenheit or a Celsius temperature scale and converts it to the other scale. Example
- 27. Reasoning: Formal statement: temperature conversion problem Input: temperature scale (Fahrenheit or Celsius), temperature Output: converted temperature Process: CelsTemp = 5/9 (FahrenTemp – 32) FahrenTemp = 9/5 CelsTemp +32 Example (Cont.)
- 28. Solution (Design the algorithm) a- The algorithm as a flow chart: START INPUT scale, temperature ConvTemp = 9/5 x temperature +32 Is scale = ‘F' ? ConvTemp = 5/9 x (temperature – 32) OUTPUT ConvTemp STOP YES NO Example (Cont.) Input: scale (F or C), temperature Output: converted temperature Process: CelsTemp = 5/9 (FahrenTemp – 32) FahrenTemp = 9/5 CelsTemp +32
- 29. The Algorithm in pseudo code: START Step 1: INPUT scale Step 2: INPUT temperature Step 3: IF scale = ‘F’ THEN ConvTemp = 5/9 x (temperature – 32) ELSE ConvTemp = 9/5 x temperature +32 ENDIF Step 4: OUTPUT ConvTemp Step 5: STOP Example (Cont.)
- 30. Test: Trace the algorithm for various values for temperatures such as 212 Fahrenheit and 100 Celsius, which are equivalent. Trace the Algorithm Example (Cont.)
- 31. Example-4: Assume that a salesperson is paid a commission based on the number of sales made during the week. The salesperson is paid a commission of $8 per sale for fewer than the established quota of 15 sales, $12 per sale if the quota is reached, and $16 per sale if the quota is exceeded. Write an algorithm to find the salesperson’s commission Assignment
- 32. The Algorithm in pseudocode: Step 1: INPUT sales Step2 : INPUT quota Step 3: IF sales < quota THEN Rate = 8 ELSE IF sales = quota THEN Rate = 12 ELSE Rate = 16 Step 4: commission = rate x sales Step 5: OUTPUT commission Step 6: STOP Draw the Flow Chart Assignment Solution
- 33. Definition of a loop: It is a piece of code that repeats again and again until some condition, called an exit condition, is met. There are different methods to implement loops such as: For, While and Repeat…..Until. This structure provides for repeated execution of part of the algorithm. III- Repetition (looping)
- 34. For Loop: Pseudo code Flow Chart FOR counter =1 to 5 PROMPT user “Enter input” GET input counter = counter +1 END FOR Counter = 0 Get input Counter=counter+1 Is Counter ≤5? YES NO III- Repetition (looping)
- 35. While Loop: Pseudo code Flow Chart PROMPT “Enter total” GET total WHILE total <= 50 PROMPT “Enter Number” GET Number total = total +Number Get Number total = total +Number Is total ≤50? YES NO Get total Repetition (looping) (Cont.)
- 36. REPEAT - UNTIL Loop: Pseudo code Flow Chart Total = 0 REPEAT PROMPT “Enter Number” GET Number total = total +Number UNTIL total > 50 Get Number total = total +Number Is total >50? YES NO Total = 0 Repetition (looping) (Cont.)
- 37. Problem Reconsider the problem in example 4 but allow for an entire sales staff. Reasoning Formal statement: sales commission problem (2) Input: number of salespeople , quota Number of sales for each salesperson Output: commission for each salesperson Process: commission = rate x number of sales Where rate is determined as: $ 8/sale for Number of sales < than 15 $12/sale for Number of sales = 15 $16/sale for Number of sales > than 15 Example 5
- 38. 1- The Algorithm in pseudocode: START Step 1: INPUT numSalespeople , quota Step 2: LOOP numSalespeople times INPUT sales IF sales < quota THEN Rate = 8 ELSE IF sales = quota THEN Rate = 12 ELSE Rate = 16 ENDIF Commission = rate x sales OUTPUT commission Step 3: STOP Solution: Example 5 (Cont.)
- 39. a) The Algorithm in Flow Chart: Start Input NumSalesperson Count = 1 Is Count < NumSalesperson? Input Sales Is Sales = quota ? ? NO Rate = 8 Rate = 12 Rate = 16 Commission = rate x sales Is Sales < quota ? YES Count = Count + 1 YES NO YES NO Output commission End Loop
- 40. Exercise (3) ECE 202 Dr. Mohamed M. Elnabawy Spring 2024 (Q.1) Design a flow chart and pseudo code that receives 2 integers and calculates/displays their Sum and Average. (Q.2) Design a flow chart and pseudo code that receives 2 integers from the user and Calculate/display their Difference, Product, and quotient. (Q.3) Design a flowchart and pseudo code that will prompt for the price of a computer and tax rate, calculate the tax and new price, and display them on the screen.
- 41. Exercise (3) Cont. ECE 202 Dr. Mohamed M. Elnabawy Spring 2024 (Q.4) Design a Flowchart and pseudo code that will prompt for the length and width of a rectangle and the radius of a circle, receive them, then calculate the area of the rectangle and the area of a circle and its circumference and display them to the screen. (Q.6) Design a flow chart and pseudo code that will prompt for 2 numbers and accept them then sort them into ascending order, and then display them on the screen. (Q.5) Design a flow chart and pseudo code that will receive 3 numbers then find the maximum and display it on the screen.
- 42. Exercise (3) Cont. ECE 202 Dr. Mohamed M. Elnabawy Spring 2024 (Q.7) Design a flow chart and pseudo code that will ask for student score in a subject, and receive it then match the score to a letter(s) grade, then display grade to the screen. the letter grade is to be calculated as follows:
- 43. Exercise (3) Cont. ECE 202 Dr. Mohamed M. Elnabawy Spring 2024 (Q.8) Design a flow chart and pseudo code that accepts pairs of integers from the user and Calculate / display their Sum, Difference, Product and quotient. The program will terminate after 5 entries. (Q.9) Design a flow chart and pseudo code that will ask for 10 temperatures expressed in degree Fahrenheit. Then it will accept each Fahrenheit temperature, then convert it into Celsius, display the converted temperature to the screen. Celsius = (Fahrenheit - 32) * 5 / 9
- 44. Exercise (3) Cont. ECE 202 Dr. Mohamed M. Elnabawy Spring 2024 (Q.10) Design a flow chart and pseudo code that will accept pairs of numbers, and calculate the sum, if the sum is +ve then display a message beside it says “The sum is positive” and if the sum is –ve then display a message beside it says “the sum is negative”. The program will terminate after 10 entries is entered. (Q.11) Design a flow chart and pseudo code that will calculate the factorial of a number and display the result.
- 45. Thanks 45 CS 101 Dr. Mohamed M. Elnabawy Fall 2025