Cheat sheet · Class 11 · CBSE · Science Computer Science
Encoding Schemes and Number System cheat sheet
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CBSE Class 11 · Computer Science
Cheat sheet
Chapter 2Encoding Schemes and Number System
Binary groups: 3 bits → one octal digit, 4 bits → one hex digit.
1. Encoding Schemes
| Scheme | Bits | Covers |
|---|---|---|
| ASCII | 7 (128 chars) | English letters, digits, symbols |
| ISCII | 8 | Indian scripts |
| Unicode (UTF-8/16/32) | variable | all world scripts |
‘A’ = 65, ‘a’ = 97, ‘0’ = 48 in ASCII.
2. Number Systems
| System | Base | Digits |
|---|---|---|
| Binary | 2 | 0–1 |
| Octal | 8 | 0–7 |
| Decimal | 10 | 0–9 |
| Hexadecimal | 16 | 0–9, A–F |
3. Conversions
- Decimal → base b: divide repeatedly by b, read remainders bottom-up.
- Base b → decimal: multiply each digit by bⁿ (place value) and add.
- Fractions to base b: multiply by b repeatedly, read integer parts top-down.
- Binary ↔ octal/hex: group bits from the binary point (3 or 4).
(25)₁₀ = (11001)₂ = (31)₈ = (19)₁₆.
4. Key Points
- Hex is compact for memory addresses and colours.
- (1011.1)₂ = 11.5
- Leading zeros don't change value.
- Unicode is a superset of ASCII.
Remember: ASCII vs Unicode | 4 bases | division & grouping methods
Encoding Schemes and Number System: questions and notes
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