Q. Show the boundary of a Word?
The boundary of a Word is defined as either 16-bits or the size of the data bus for the processor, and a Double Word is Two Words. so, a Word and a Double Word is not a fixed size but varies from system to system depending on the processor. Though, for our discussion, we will define a word as two bytes.
For the 8085 micro processor and 8086 micro processor, a word is a group of 16 bits, We will number the bits in a word starting from bit zero (b0) through fifteen (b15) as follows:
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b15
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b14
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b13
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b12
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b11
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b10
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b9
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b8
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b7
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b6
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b5
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b4
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b3
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b2
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b1
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b0
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Like the byte, bit 0 is the least significant bit (LSB) and bit 15 is the most significant bit MSB. While referencing the other bits in a word use their bit position number.
Notice that a word contains precisely two bytes. The Bits b0 through b7 form the low order byte, bits 8 through 15 form the high order byte. It naturally, a word may be further broken down into four nibbles. The Nibble zero is the low order nibble in the word and nibble three is the high order nibble of the word and The other two nibbles are "nibble one" or "nibble two".
With a 16 bits, you can represent 2^16 (65,536) different values. These might be the unsigned numeric values in the range of 0 => 65,535, signed numeric values in the range of -32,768 => +32,767 or any other data type with no more than 65,536 values. The three main uses for words are
- 16-bit integer data values
- 16-bit memory addresses
- any number system requiring 16 bits or less