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The Bit
A Bit is the smallest unit of data on a binary computer. A single bit is capable of representing only one value, either 0 or 1. If you are using a bit to represent a Boolean (True/False) value then that bit represents true or false.
The Nibble
The Nibble specially comes in the area of interest when we are talking about the number systems, BCD (Binary Coded Decimal) or/and hexadecimal (base 16) numbers.
A nibble is a collection of bits on a 4-bit boundary. It takes four bits to represent a single BCD or hexadecimal digit. With a nibble, we can represent up to 16 distinct values.
In the case of hexadecimal numbers, the values 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F are represented with four bits. BCD uses ten different digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) and requires four bits.
In fact, any sixteen distinct values can be represented with a nibble but hexadecimal and BCD digits are the primary items we can represent with a single nibble. The bit level representation of nibble will be as follows:
The Byte
The Byte is the most important data structure used by 80x86 microprocessor. A byte consists of eight bits and is the smallest addressable data item in the microprocessor. The Main memory and I/O addresses in the computer are all byte addresses and thus the smallest item that can be individually accessed by an 80x86 microprocessor programs is an 8-bit value.
To access anything smaller requires that you read the byte containing the data and mask out the unwanted bits. We shall do the programming to do this in the next chapters.
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