Computer – Fundamentals of Computer

Binary System – Bit vs Byte

What is Binary System :   A system in which information can be expressed by combinations of the digits 0 and 1.  The modern day origin of this can be traced to  late 1930s,  when Claude Shannon showed that it was possible to carry out logical operations by assigning the  number 1 to “true” and 0 to “false” while  using switches which were closed for “true” and open for “false,”.

What is Bit? Or What is Bits ? : The term  bit or bits means“binary digit“, meaning 0 or 1 in binary numbering.  .  Thus, we can say that it is the smallest unit of information which can be manipulated by a digital machine. (While writing in short form we merely use a lowercase b to represent bits).  With two bits, you can have four different states (2*2):

0	0	0	0
0	1	0	1
1	0	1	0
1	1	1	1

With 3 bits, you can have eight different states (2*2*2), and so on.   Thus, for a group of n bits, it is possible to represent 2ⁿvalues.

What is Byte? : The byte is a unit of information composed of 8 bits. It can be used to store, among other things, a character, such as a letter or number.  (While writing in short form we merely use an uppercase B to represent a byte).

For a byte, the smallest number possible is 0 (represented by eight zeroes, 00000000), and the largest is 255 (represented by eight ones, 11111111), making for 256 different possible values.

The data and instructions (code) that a CPU uses are coded into bytes. For example,  capital letter ‘A’ in ASCII (PC) code is byte 0100 0001. A lower case ‘a’ is byte 0110 0001.

A 16-bit unit of information is usually called a word.

A 32-bit unit of information is called a double word (sometimes called a dword).

Tips :

Bit Vs Byte :

A bit is always represented by a small “b”, a Byte is always represented by a large “B”.

It has become common practice to use bits in reference to interface speeds and bytes in reference to memory and storage capacities.

Kilobytes and Megabytes :

Till  1998 , the following system for presenting various values was prevalent (Some softwares still use the  following system)

·         One kilobyte (kB) = 2¹⁰ bytes = 1024 bytes

·         One megabyte (MB) = 2²⁰ bytes = 1024 kB = 1,048,576 bytes

·         One gigabyte (GB) = 2³⁰ bytes = 1024 MB = 1,073,741,824 bytes

One terabyte (TB) = 2⁴⁰ bytes = 1024 GB = 1,099,511,627,776 bytes

However, in December 1998, , the International Electro technical Commission weighed in on the issue and issued new guidelines which are known as  IEC’s standardised units.

·         One kilobyte (kB) = 1000 bytes

·         One megabyte (MB) = 1000 kB = 1,000,000 bytes

·         One gigabyte (GB) = 1000 MB = 1,000,000,000 bytes

·         One terabyte (TB) = 1000 GB = 1,000,000,000,000 bytes

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The earlier system of representing bytes has been redefined by IEC and is known as binary kilo (kibi), binary mega (mebi), binary giga (gibi), and binary tera (tebi).   They are defined as:

·         One kibibyte (kiB) is worth 2¹⁰ = 1024 bytes

·         One mebibyte (MiB) is worth 2²⁰ = 1,048,576 bytes

·         One gibibyte (GiB) is worth 2³⁰ = 1,073,741,824 bytes

·         One tebibyte (TiB) is worth 2⁴⁰ = 1,099,511,627,776 bytes