NCERT Class 11 Computer Science Computer Science: Chapter 2 — Encoding Schemes and Number System
This chapter, "Encoding Schemes and Number System," from NCERT Class 11 Computer Science, introduces how computers interpret human-readable data like keyboard inputs. It explains that computers understand only binary (0s and 1s) and thus, keyboard characters are mapped to unique codes, then converted to binary. The chapter defines encoding as the process of converting data into an equivalent cipher using specific codes. It highlights the importance of standard encoding schemes like ASCII (American Standard Code for Information Interchange), which assigns unique codes to characters, ensuring consistent communication between computers. ASCII, initially using 7 bits, can represent 128 characters and is widely used for the English language. The chapter also touches upon encryption and decryption.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 11 |
| Subject | Computer Science |
| Book | Computer Science |
| Chapter | Chapter 2 — Encoding Schemes and Number System |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 3 minutes |
| Word count | 554 |
Learning outcomes
- Understand the concept of data encoding and its necessity for computers.
- Learn about standard encoding schemes like ASCII.
- Recognize how keyboard inputs are converted into binary for computer processing.
- Understand the role of unique codes in character representation.
Vocabulary
| Word | Meaning |
|---|---|
| Encoding | The mechanism of converting data into an equivalent cipher using a specific code. |
| Cipher | Something converted to a coded form to hide or conceal it. |
| Encryption | The process of converting data into a cipher. |
| Decryption | The process of converting a cipher back to its original form. |
| ASCII | American Standard Code for Information Interchange, a character encoding standard. |
| Binary | A number system with base 2, using only digits 0 and 1. |
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Practice questions
- What is encoding? Answer: Encoding is the mechanism of converting data into an equivalent cipher using a specific code.
- Why is encoding necessary for computers? Answer: Computers understand only binary language (0s and 1s), so human-readable data must be encoded into a format they can process.
- What does ASCII stand for and what is its purpose? Answer: ASCII stands for American Standard Code for Information Interchange. Its purpose is to standardize the representation of characters on keyboards.
- How many characters can be encoded by a 7-bit ASCII code? Answer: A 7-bit ASCII code can encode 2^7 = 128 different characters.
Frequently asked questions
How do computers understand characters typed on a keyboard?
Computers understand only binary language. When a key is pressed, it's mapped to a unique code, which is then converted into binary for the computer to process.
What is the role of encoding schemes like ASCII?
Encoding schemes like ASCII assign a unique code to each character (letters, numbers, symbols), ensuring that different keyboards and computers represent them consistently.
What does ASCII stand for?
ASCII stands for American Standard Code for Information Interchange.
How many characters can be represented using 7-bit ASCII?
Using 7 bits, ASCII can represent 2^7, which equals 128 different characters.
Is ASCII used for languages other than English?
Initially, ASCII was designed for the English language character set. For other languages, different or extended encoding schemes are used.
What is the difference between encoding and encryption?
Encoding converts data into a specific code for computer processing. Encryption converts data into a cipher to hide it, which can then be decrypted back to the original form.
Related resources
Important topics
Topics covered
NCERT Class 11 Computer Science — Computer Science — Chapter 2 — Encoding Schemes and Number System. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.