Programming Fundamentals

Subject: Computer Science
Topic: 5
Cambridge Code: 0478

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Programming Basics

Program - Set of instructions for computer

Programming Languages

Levels:

• High-level: Python, Java, JavaScript (human-friendly)
• Low-level: Assembly (machine-oriented)

Types:

• Imperative: Step-by-step instructions (Python, Java)
• Declarative: Describe what to do (SQL)
• Object-oriented: Objects and classes (Java, C++)
• Functional: Functions and immutability (Haskell, Scheme)

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Variables and Data Types

Variables

Variable - Named storage location

Naming conventions:

• Start with letter or underscore
• Alphanumeric + underscore
• Case-sensitive
• Meaningful names

Declaration: Reserve memory and assign type

name = "Alice"
age = 25
score = 95.5

Data Types

Integer:

• Whole numbers: -100, 0, 25, 1000
• Operations: +, -, *, //, %

Float (Real):

• Decimal numbers: 3.14, -0.5, 99.99
• Operations: +, -, *, /

String:

• Text: "Hello", "2024"
• Operations: Concatenation, slicing, length

Boolean:

• True or False
• Logical operations: AND, OR, NOT

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Operators

Arithmetic Operators

Operator	Name	Example
+	Addition	5 + 3 = 8
-	Subtraction	5 - 3 = 2
*	Multiplication	5 * 3 = 15
/	Division	15 / 3 = 5
//	Integer division	15 // 4 = 3
%	Modulo (remainder)	15 % 4 = 3
**	Exponentiation	2 ** 3 = 8

Comparison Operators

Operator	Meaning	Example
==	Equal	5 == 5 → True
!=	Not equal	5 != 3 → True
>	Greater than	5 > 3 → True
<	Less than	5 < 3 → False
>=	Greater or equal	5 >= 5 → True
<=	Less or equal	3 <= 5 → True

Logical Operators

Operator	Meaning	Example
AND	Both true	True AND False → False
OR	At least one true	True OR False → True
NOT	Inverts	NOT True → False

Assignment Operators

x = 5        # Assignment
x += 3       # x = x + 3
x -= 2       # x = x - 2
x *= 2       # x = x * 2

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Control Flow

If-Else Statements

Conditional execution based on conditions

if age >= 18:
    print("Adult")
elif age >= 13:
    print("Teenager")
else:
    print("Child")

Loops

For Loop - Fixed iterations

for i in range(1, 6):  # 1 to 5
    print(i)

While Loop - Conditional iterations

count = 0
while count < 5:
    print(count)
    count += 1

Loop Control:

• break: Exit loop
• continue: Skip to next iteration

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Functions

Function - Reusable block of code

Definition and Calling

def greet(name):
    return f"Hello, {name}!"

message = greet("Alice")  # Calling
print(message)  # Hello, Alice!

Parameters and Arguments

Parameters: Variables in function definition Arguments: Values passed when calling

def add(a, b):           # Parameters
    return a + b

result = add(5, 3)       # Arguments

Return Values

def circle_area(radius):
    import math
    area = math.pi * radius ** 2
    return area         # Returns value

Scope

Local scope: Variables defined inside function Global scope: Variables defined outside functions

x = 10  # Global

def func():
    y = 5  # Local
    print(x)  # Can access global
    print(y)

# print(y)  # ERROR: y not accessible

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Data Structures

Lists (Arrays)

Ordered collection of elements

numbers = [1, 2, 3, 4, 5]
names = ["Alice", "Bob", "Charlie"]

numbers[0]     # 1 (access)
numbers[1:3]   # [2, 3] (slicing)
numbers.append(6)  # Add element

Dictionaries

Key-value pairs

person = {
    "name": "Alice",
    "age": 25,
    "city": "NYC"
}

person["name"]  # "Alice"
person["age"] = 26  # Update

Tuples

Immutable list

coordinates = (10, 20)
color = (255, 128, 0)  # RGB

coordinates[0]  # 10
# coordinates[0] = 15  # ERROR: Cannot modify

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String Operations

String Methods

text = "Hello World"

text.lower()        # "hello world"
text.upper()        # "HELLO WORLD"
text.replace("World", "Alice")  # "Hello Alice"
text.split()        # ["Hello", "World"]
len(text)           # 11

String Formatting

name = "Alice"
age = 25

# Concatenation
message = "Name: " + name + ", Age: " + str(age)

# Format string (modern Python)
message = f"Name: {name}, Age: {age}"

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Input and Output

Input

name = input("What's your name? ")
age = int(input("How old are you? "))

Output

print("Hello, world!")
print(f"Name: {name}, Age: {age}")

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Comments and Documentation

Comments

# Single-line comment

"""
Multi-line comment
or docstring
"""

Docstrings

def add(a, b):
    """Add two numbers and return sum."""
    return a + b

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Key Points

1. Variables store data of specific types
2. Data types: Integer, Float, String, Boolean
3. Operators: Arithmetic, Comparison, Logical
4. Control flow: if-else, for, while
5. Functions encapsulate reusable code
6. Lists/arrays: Ordered collections
7. Dictionaries: Key-value storage
8. Strings: Text with manipulation methods

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Practice Questions

1. Write variable declarations
2. Write arithmetic expressions
3. Create if-else statements
4. Write for and while loops
5. Define and call functions
6. Use lists and dictionaries
7. Manipulate strings

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Revision Tips

• Practice variable naming
• Know operator precedence
• Understand control flow
• Practice function writing
• Know data structure uses
• Test code frequently
• Use meaningful names