Codes — Digital Logic -

💻 Basics of Digital Logic (Codes)

Imagine you’re sending a message to your friend in secret.
You both agree on a way to hide your words using special symbols so that only you two understand them.
That’s what codes do in the digital world — they let computers store, send, and understand information using patterns of 0s and 1s.

💡 What Are Codes in Digital Logic?

In simple terms, a code is a way of representing information (like numbers, letters, or symbols) using a specific combination of binary digits (bits) — 0s and 1s.

Since computers only understand these two values, everything we type — text, sound, or images — has to be converted into binary form using different coding methods.

So, codes are like languages that bridge human understanding and machine logic.

🧠 Why Do We Need Codes?

Think about how we humans use different languages — English, Hindi, Chinese — to communicate.
Computers do the same, but their “language” is binary.
Codes help computers:

Represent numbers, alphabets, and characters
Detect and correct errors in data
Simplify arithmetic and logical operations
Store information efficiently

Without codes, digital communication would be confusing and unreliable.

🔹 Types of Codes in Digital Logic

Let’s explore the main ones in a simple way:

1. Binary Codes

This is the most basic type of code.
Each number or symbol is written as a unique combination of binary digits.

Example:
Decimal numbers can be represented in binary form:

0 → 0000
1 → 0001
2 → 0010
3 → 0011
… and so on.

These are the building blocks for all other coding systems.

2. BCD (Binary Coded Decimal)

BCD means each decimal digit (0–9) is represented by its 4-bit binary equivalent.

Example:
Decimal number 57 →
5 = 0101
7 = 0111
So, (57)₁₀ = 0101 0111 in BCD.

This makes it easy for digital devices like calculators to handle decimal numbers directly without converting to pure binary form.

3. Gray Code

Gray Code is a special binary code where only one bit changes between two consecutive numbers.
This reduces errors in systems like rotary encoders and sensors.

Example:

Decimal	Binary	Gray
0	000	000
1	001	001
2	010	011
3	011	010

So, Gray Code prevents mistakes when signals change quickly — like a speedometer needle moving between two positions.

4. Excess-3 Code

Excess-3 is a self-complementing code used for decimal digits.
It’s created by adding 3 to the actual decimal number and then converting it to binary.

Example:
Decimal 5 → 5 + 3 = 8 → (1000)₂
Decimal 9 → 9 + 3 = 12 → (1100)₂

This property makes arithmetic operations simpler for digital circuits.

5. ASCII Code (American Standard Code for Information Interchange)

ASCII is how computers represent text characters.
Every letter, number, or symbol has its own 7-bit (or sometimes 8-bit) binary code.

Examples:

‘A’ → 65 → (1000001)₂
‘B’ → 66 → (1000010)₂
‘a’ → 97 → (1100001)₂

Whenever you type something on a keyboard, ASCII helps the computer recognize which key you pressed.

6. Unicode

While ASCII covers English characters, Unicode expands the range to include symbols, emojis, and languages from around the world — making computers truly global in communication.

🧩 Real-Life Analogy

Think of codes like different writing systems.
The same word “Hello” can be written as “Hola” (Spanish) or “नमस्ते” (Hindi).
The meaning stays the same — only the representation changes.
Similarly, in digital logic, codes help represent information in various ways without changing its meaning.

Codes are patterns of 0s and 1s that represent information for computers.
They make communication, data storage, and arithmetic operations easier and error-free.
Common digital codes include Binary, BCD, Gray, Excess-3, ASCII, and Unicode.
Understanding codes helps us see how computers “read,” “write,” and “think” in their own language.