2.6 Actions

Definition: Sequence is when instructions are executed one after another in order.

Purpose: To ensure steps happen in the correct order.

When used: In all programs where actions must follow a logic flow.

Python example:

print("Start program")
x = 5
y = 10
total = x + y
print(total)
        

Definition: Selection allows different actions based on conditions.

Purpose: Decision‑making in programs.

When used: When different outcomes are needed.

Python example (if / elif / else):

score = 65

if score >= 70:
    print("Distinction")
elif score >= 50:
    print("Pass")
else:
    print("Fail")
        

Python example (match / case):

day = "Monday"

match day:
    case "Monday":
        print("Start of week")
    case "Friday":
        print("End of week")
    case _:
        print("Midweek")
        

Definition: Loops repeat actions while a condition is met.

Types:

• Count‑controlled loops (for)
• Condition‑controlled loops (while)

For loop example:

for i in range(1, 6):
    print(i)
        

While loop example:

count = 1

while count <= 5:
    print(count)
    count += 1
        

Benefits:

• Reduce repeated code
• Improve efficiency
• Handle large datasets easily

Drawbacks:

• Infinite loops if conditions are incorrect
• Logic errors if misused

Interpreting code means understanding what it will do.

Example:

total = 0

for i in range(3):
    total += i

print(total)
        

This loop adds 0, 1, and 2.

Python example:

number = int(input("Enter a number: "))

if number % 2 == 0:
    print("Even")
else:
    print("Odd")
        

Incorrect code:

count = 1

while count <= 5:
print(count)
count += 1
        

Problems:

• Indentation error
• Loop body incorrectly structured

Corrected code:

count = 1

while count <= 5:
    print(count)
    count += 1