Computer Science Basics for Beginners

🧠 Variables & Memory Mapping

Variables are one of the most fundamental building blocks in programming. They act as named storage locations in memory that hold values used by your program. Understanding how variables work and how they map to memory is critical to writing efficient, bug-free code.

📝 What is a Variable?

A variable is a label or name that refers to a value stored in computer memory. It allows you to store, access, and manipulate data in your program.

// Python
name = "Alice"
age = 25
  

• name is a variable storing a string "Alice"
• age is a variable storing a number (integer) 25

📦 How Variables Map to Memory

When a variable is declared and assigned a value, the computer assigns a memory address to hold that value. The variable name acts as a reference to that memory address.

• Each variable points to a location in RAM
• Data types affect how much memory is allocated
• Variables can be changed and reused

🧠 Memory Layout Example

Variable   Value   Memory Address
--------   -----   ---------------
x          10      0x1001
y          20      0x1005
name     "Ali"     0x1010
  

🧮 Types of Variables

• Local Variable: Defined inside a function or block
• Global Variable: Defined outside all functions
• Constant: Value doesn’t change (e.g., PI = 3.14)

🧬 Variable Naming Rules

• Must begin with a letter or underscore
• Cannot use special characters (like @, #, %)
• Case-sensitive (e.g., name ≠ Name)
• Choose meaningful names (e.g., total_price not x1)

🎯 Why Understanding Memory Matters?

• Prevents memory leaks
• Improves program efficiency
• Helps in understanding pointers, references, garbage collection

💡 Real-Life Analogy

Think of memory as a row of lockers. Each locker has a number (address), and you place a value (like a file or item) in it. The variable name is like labeling a key that tells you which locker contains your stuff.

🧪 Bonus Tip: Inspecting Memory

# Python Example
x = 42
print(id(x))  # prints memory address
  

📝 Practice Questions

1. What is a variable and how does it relate to memory?
2. Explain the difference between local and global variables.
3. Why is understanding memory mapping important?
4. What is the output of id("hello") in Python?

✅ Coming Next

In the next chapter, we’ll learn how to plan logic in coding using Algorithms & Flowcharts.