Tags: #◇Computer Science #◇CSARCH1 #◇Computer Architecture #◇Data Representation #◇Binary Data Organization
Binary Data Organization
◇Overview
This module explains the different levels of binary data organization and the difference between Little Endian and Big Endian byte ordering.
◇Binary Data Units
| Organization | Number of bits | Usage / Notes |
|---|---|---|
| Bit | 1 bit (0 or 1) | Basic unit (binary digit). Abbreviated as b. |
| Crumb | 2 bits | Largely defunct term, rarely used. |
| Nibble | 4 bits | Represents a Hex digit or BCD digit. |
| Byte | 8 bits | Smallest addressable data unit. Abbreviated as B. |
| Half word | 16 bits | Definition is architecture-dependent. |
| Word | 32 bits | In 32-bit architecture, 1 word = 32 bits. |
| Double word | 64 bits | |
| Quad word | 128 bits |
◇Significant Bits and Bytes
- Most Significant Bit (MSb): The bit with the highest positional value (e.g., bit 7 in a byte).
- Least Significant Bit (LSb): The bit with the lowest positional value (e.g., bit 0 in a byte).
- Note: Computer architecture convention dictates that numbering starts at 0.
- Concepts of significance extend to nibbles, bytes, and words (e.g., LSB for Least Significant Byte, MSB for Most Significant Byte).
- Example: In the hex number
123ACAFE16:
- Example: In the hex number
FE16is the Least Significant Byte (LSB).1216is the Most Significant Byte (MSB).
◇Endianness
Endianness refers to the convention used to interpret the byte ordering of multi-byte data stored in computer memory.
- Coined by Danny Cohen, based on Jonathan Swift's "Gulliver's Travels".
Little Endian
- Stores the least-significant byte at the lowest memory address, followed by other bytes in ascending order of significance.
- The address of the multi-byte data is the address of its least-significant byte.
- Example: Storing 32-bit hex data
55443322starting at address0000:0000: 220001: 330002: 440003: 55
Big Endian
- Stores the most-significant byte at the lowest memory address, followed by other bytes in ascending order of significance.
- The address of the multi-byte data is the address of its most-significant byte.
- Example: Storing 32-bit hex data
22334455starting at address0000:0000: 220001: 330002: 440003: 55
◇References & Navigation
- Previous Topic: ◇2x vs 10y Ambiguity-1
- Next Topic: ◇Binary Codes for Decimal Digits
ACTIVE RECALL VERIFICATION
Select an answer to verify conceptual comprehension and reveal the technical rationale.
What is the smallest addressable data unit in most computer architectures?
How many bits are contained in a "Nibble"?
In a standard byte, which bit is considered the most significant bit (MSb)?
What does the term "Endianness" refer to in computer architecture?
In a Little Endian system, where is the least-significant byte stored?
If the 32-bit hex data 55443322 is stored at address 0000 in a Little Endian system, what is the content of address 0001?
For the hexadecimal number 123ACAFE16, what is the most significant byte (MSB)?
Who coined the terms Big Endian and Little Endian based on a novel by Jonathan Swift?
If address 0000 contains 22, 0001 contains 33, 0002 contains 44, and 0003 contains 55, what is the 32-bit data read in a Big Endian system?
In computer architecture conventions, what number does bit indexing typically start at?