Algorithms, Flowcharts, Pseudocode & Dry Run

Course: Algorithms, Flowcharts, Pseudocode & Dry Run

---

1. Algorithm

• Definition: An algorithm is a step-by-step method to solve a problem or perform a specific task.
• Key Points:
  • Each step must be clear and ordered properly.
  • It must produce the correct result.
  • It should finish after a limited number of steps.

Example: Find Greater Number

1. Start
2. Input A, B
3. If A > B → Print "A is greater"
4. Else → Print "B is greater"
5. Stop

---

2. Flowchart

• Definition: A flowchart is a visual diagram that shows the steps of an algorithm using symbols.
• Common Symbols:
  • Oval → Start / End
  • Parallelogram → Input / Output
  • Rectangle → Process
  • Diamond → Decision (Yes/No)
  • Arrow → Flow of control

Example: Check Even or Odd Number

1. Start
2. Input Number
3. Is Number % 2 == 0?
4. If Yes → Print "Even"
5. If No → Print "Odd"
6. End

---

3. Pseudocode

• Definition: Pseudocode is writing an algorithm in simple English-like steps before coding.
• Advantages:
  • Easy to understand
  • No syntax errors
  • Helps in planning logic

Example: Check Even or Odd

START
Input num
IF num % 2 == 0 THEN
   PRINT "Even"
ELSE
   PRINT "Odd"
END

---

4. Dry Run

• Definition: Dry run means checking your algorithm or code manually, step by step, using sample data.
• Purpose:
  • Find logic mistakes.
  • Understand program flow.

Example: Check Positive or Negative

x = -5
IF x > 0 THEN
    PRINT "Positive"
ELSE
    PRINT "Negative"

Dry Run Table:

Step	Statement	x	Output
1	x = -5	-5	-
2	x > 0 ?	-5	False
3	Else → Print "Negative"	-5	Negative

Final Output: Negative

---

5. Example Algorithms, Flowcharts, and Pseudocodes

Example 1: Check Greater Number

Algorithm:
1. Start
2. Input A, B
3. If A > B → Print "A is greater"
4. Else → Print "B is greater"
5. Stop

Pseudocode:
START
Input A, B
IF A > B THEN PRINT "A is greater"
ELSE PRINT "B is greater"
END

Example 2: Nested Loops

Algorithm:
1. Start
2. For i = 1 to 3
   For j = 1 to 2
       Print i, j
3. Stop

Pseudocode:
START
FOR i = 1 TO 3
   FOR j = 1 TO 2
       PRINT i, j
END FOR
END

Example 3: Nested Conditions

Algorithm:
1. Start
2. Input x
3. If x > 0
     If x % 2 == 0 → Print "Positive Even"
     Else → Print "Positive Odd"
   Else → Print "Negative or Zero"
4. Stop

Example 4: Series 5,10,15,20,25,30

Algorithm:
1. Start
2. For i = 5 to 30 step 5
     Print i
3. Stop
Output: 5 10 15 20 25 30

Example 5: Series 1,4,9,16,25,36,49,64

Algorithm:
1. Start
2. For i = 1 to 8
     Print i * i
3. Stop
Output: 1 4 9 16 25 36 49 64

Example 6: Fibonacci Series (0,1,1,2,3,5,8,13,21)

Algorithm:
1. Start
2. Set a = 0, b = 1
3. Print a, b
4. For i = 3 to n
      c = a + b
      Print c
      a = b
      b = c
5. Stop
Output: 0 1 1 2 3 5 8 13 21

Example 7: Finding Factorial

Algorithm:
1. Start
2. Input n
3. Set fact = 1
4. For i = 1 to n
      fact = fact * i
5. Print fact
6. Stop
Output: For n = 5 → 120

Example 8: Bubble Sort

Algorithm:
1. Start
2. Input list of numbers
3. Repeat (n-1) times
4. For i = 0 to n-2
     If list[i] > list[i+1], swap them
5. Print sorted list
6. Stop
Example Input: [5, 2, 4, 1]
Output: [1, 2, 4, 5]

Example 9: ATM Withdraw Machine

Algorithm:
1. Start
2. Input PIN
3. If PIN is correct
     Display Menu: Withdraw, Balance, Exit
     If Withdraw → Input amount
        If amount <= balance → Dispense cash & update balance
        Else → Print "Insufficient Balance"
   Else → Print "Wrong PIN"
4. Stop

Pseudocode:
START
Input PIN
IF PIN == 1234 THEN
   PRINT "1.Withdraw 2.Balance 3.Exit"
   Input choice
   IF choice == 1 THEN
       Input amount
       IF amount <= balance THEN PRINT "Cash Dispensed"
       ELSE PRINT "Insufficient Balance"
   ENDIF
ELSE
   PRINT "Invalid PIN"
END