✅ Understand the purpose of character encoding standards.
✅ Differentiate between ASCII and Unicode.
Why Binary? 💡
Computers don't understand words. They understand electricity.
At the most basic level, a computer circuit can be in one of two states:
ON (electricity is flowing)
OFF (no electricity)
We represent these two states using numbers:
ON = 1
OFF = 0
This two-digit system (0 and 1) is called the Binary System, and it's the fundamental language of all digital computers.
Try It: Binary Switches
Click each circuit switch. Watch how ON maps to 1 and OFF maps to 0.
0
0
0
0
Binary digits: 0000
Each switch = one binary digit (bit)
Bits and Bytes: The Building Blocks
All data (text, images, sound) is broken down into these simple units.
Bit (Binary Digit)
The smallest possible unit of data.
0 or 1
Byte
A group of 8 bits.
01000001
A single byte can represent 256 (28) different values.
Try It: Build a Byte
Click the 8 bit buttons to flip them. See the decimal value of the byte you build.
2726252423222120
Decimal value: 0 / 255 max
Measuring Data Storage 📊
The byte is the standard unit for measuring digital storage.
Kilobyte (KB) ≈ 1,000 bytes
(A plain text email)
Megabyte (MB) ≈ 1 million bytes
(A high-quality photo or MP3 song)
Gigabyte (GB) ≈ 1 billion bytes
(A standard-definition movie)
Terabyte (TB) ≈ 1 trillion bytes
(The storage of a typical modern laptop)
Quiz: Match the Data Unit
Select the correct storage unit for each scenario, then check your answers.
Scenario
Your Answer
A plain text email
A high-quality photo or MP3 song
A standard-definition movie
A typical modern laptop's full storage
Representing Text: The Challenge
How does a computer understand the letter 'A' or the symbol '?'
It uses Character Encoding Standards: a dictionary that maps each character to a unique binary number.
'A' ➡️ [Encoding Standard] ➡️ 01000001
The First Standard: ASCII
ASCII (American Standard Code for Information Interchange)
An early, widely adopted standard.
Uses 7 or 8 bits per character.
Can represent 128 characters:
Uppercase English (A-Z)
Lowercase English (a-z)
Numbers (0-9)
Common punctuation (!, @, #, etc.)
Example: In ASCII, the character 'A' is represented by the number 65, which is 01000001 in binary.
Try It: ASCII Lookup
Type a single letter or digit and see its ASCII decimal code and binary representation.
Enter a character above
The Problem with ASCII 🌍
ASCII was great for English, but what about other languages?
Nepali (नेपाली)
नमस्ते
Japanese (日本語)
こんにちは
Arabic (العربية)
مرحبا
Limitation: With only 128-256 possible values, ASCII cannot represent characters from most of the world's languages.
The Universal Solution: Unicode
Unicode is a modern standard designed to fix ASCII's limitations.
Its goal is to represent every character from every language.
It can represent over 1 million unique characters (including emojis! 👍🎉).
It is the dominant standard for the web, modern operating systems, and software development.
The most common implementation of Unicode is UTF-8, which is backward compatible with ASCII.
ASCII vs. Unicode at a Glance 🔍
ASCII
Scope: English-centric
Size: 7 or 8 bits
Characters: 128-256
Use: Legacy systems
Unicode (UTF-8)
Scope: Universal (All languages)
Size: Variable (1-4 bytes)
Characters: Over 149,000+
Use: Modern standard
Quiz: ASCII or Unicode?
For each situation, choose whether ASCII or Unicode is the right choice.
1. Sending an English-only plain text file in 1985.
2. A Nepali government website displaying Devanagari text.
3. An app that needs to support Japanese, Arabic, and emoji.
4. A legacy system that only uses uppercase English letters A-Z.
What About Programs?
Just like data, program instructions must also be in binary for the CPU to execute them.
High-Level Code (Human-readable)
print("Hello, World!")
⬇️
A Compiler or Interpreter translates the code.
⬇️
Machine Code (Binary)
01101000 01100101 01101100 ...
Practical Application in Nepal 🇳🇵
Language and Script: The Nepali language uses the Devanagari script (e.g., क, ख, ग). ASCII cannot represent these characters.
Digital Nepal: Unicode (UTF-8) is essential for all digital services in Nepal, from government websites and the Nagarik App to news portals and social media. It allows us to type and read in Nepali online.
Tech Market: When buying a phone or laptop in Nepal, storage capacity (measured in GB or TB) is a key factor, determining how many photos, videos, and apps you can store.
Key Takeaways ⚡
Computers represent everything using the binary system (0s and 1s) because of their electronic nature (on/off).
A bit is a single 0 or 1. A byte is a group of 8 bits and is the standard unit for measuring storage.
ASCII is an older, limited encoding for English text.
Unicode is the modern, universal standard that supports all world languages, including Nepali.
Program code must be compiled into binary machine code before a computer can run it.
Exam Practice: Short Answer
Define bit and byte. How many bytes are in 1 KB?
Convert 25 (decimal) to binary and 10110 (binary) to decimal.
Differentiate between ASCII and Unicode.
Exam Practice: Long Answer
Explain how computers represent numbers, text, images, and sound.
What are character encoding standards? Why is Unicode important for languages like Nepali?
Revise the chapter note before writing these answers.