Abbreviations like Kb, KB, Mb and GB are often confused, misunderstood or used incorrectly. Here’s a brief explanation of proper usage.

Let’s start at the beginning. The only data that a computer can understand is on (1) and off (1). But those two simple commands can be grouped into millions of combinations and it is the way they are grouped in series that creates complex data.

The basic unit is called a bit (binary digit). Each bit has an electronic switch, or gate. If the gate is open the bit is on and electricity can go through. The computer reads on or open switches as a number 1. If the gate is closed or off, the electricity is blocked and the computer reads off bits as 0.

Bits can be grouped together to allow more complex code. Eight bits are grouped together to form a byte. This allows 256 possible combinations of 1/0. The abbreviation for bit is a lowercase “b”; the abbreviation for byte is an uppercase “B”. Bits and bytes can then be expressed in larger measurements. They are generally expressed in exponents of two, known as binary code

The Standards

Although computer data is normally measured in binary code, the prefixes for the multiples are based on the metric system. The nearest binary number to 1,000 is 2^10 or 1,024; thus 1,024 bytes was named a Kilobyte. So, although a metric “kilo” equals 1,000 (e.g. one kilogram = 1,000 grams), a binary “Kilo” equals 1,024 (e.g. one Kilobyte = 1,024 bytes). Not surprisingly, this has led to a great deal of confusion.

In December 1998, the International Electrotechnical Commission (IEC) approved a new IEC International Standard. Instead of using the metric prefixes for multiples in binary code, the new IEC standard invented specific prefixes for binary multiples made up of only the first two letters of the metric prefixes and adding the first two letters of the word “binary”. Thus, for instance, instead of Kilobyte (KB) or Gigabyte (GB), the new terms would be kibibyte (KiB) or gibibyte (GiB).

Sometimes in the routine life, just a few abbreviations involved with our activity, it’s like about bits,B ytes, KBytes and the end GBytes, it’s not underestimated fact, if we far from ZByte and up.

In other case, when question comes during on my study, which that Subnetting or in Network design activity, record data stream capture or any field’s are involve the abbreviations meter, sincerely I’ve been stack or confused, little forget exactly, 😉 which one that’s correctly to calculate the metric.

but, come on !! soon you will be graduate man, how could you answer if your knowledge about abbreviations and the role of it ‘s none, where’s your basically
By the way, here are brief summaries of the Old Standard and the IEC Standard:

IEC Standard 1 bit (bit) = 0 or 1 = one binary digit

1 Octet = Always 8 bits
1 kilobit (kbit) = 10^3 bits = 1,000 bits

1 megabit (Mbit) = 10^6 bits = 1,000,000 bits

1 gigabit (Gbit) = 10^9 bits = 1,000,000,000 bits

1 terabit (Tbit) = 10^12 bits = 1,000,000,000,000 bits

1 petabit (Pbit) = 10^15 bits = 1,000,000,000,000,000 bits

1 exabit (Ebit) = 10^18 bits = 1,000,000,000,000,000,000 bits

1 zettabit (Zbit) = 10^21 bits = 1,000,000,000,000,000,000,000 bits

1 yottabit (Ybit) = 10^24 bits = 1,000,000,000,000,000,000,000,000 bits

Binary to Decimal Conversion to Decimal Conversion
Converting binary to decimal examples:


128 64 32 16 8 4 2 1: Bit values
0 0 0 0 0 0 0 0 = 0
1 1 1 1 1 1 1 1 = 255
0 0 0 0 1 1 1 1 = 15
0 1 0 1 0 1 0 1 = 85
1 0 0 0 0 0 1 1 = 131
0 0 0 1 0 1 1 0 = 22

Binary (Cont.) (Cont.)
Bits Binary Decimal

0 00000000 0
1 10000000 128
2 11000000 192
3 11100000 224
4 11110000 240
5 11111000 248
6 11111100 252
7 11111110 254
8 11111111 255

Math to Memorize! to Memorize!
Subnet mask First Subnet’


256-192 =64
256-224 =32
256-240 =16
256-248 =8
256-252 =4

Powers of 2 Powers of 2

2^1=2
2^2=4
2^3=8
2^4=16
2^5=32
2^6=64
2^7=128
2^8=256


Courtesy of : Globalnet Training Inc. – CCNA/DA Copyright 2002/2003

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