Computable Minds -

How they swindle us with the Megabits, Megabytes and Mebibytes

Posted on: Sep, 3rd 2010
Binary code
There is a big lack of knowledge about how is measured the quantity of information in a computer. It is a fact that storage device sellers and Internet providers have take advantage to cheat us. Also, not a lot of time ago was changed the nomenclature of the international system of information units generating even more confusion.

- The bit:

In first place I'm going to explain the basic unit information, the bit, concept invented by Clude E. Shannon in 1948. The bit can represent any two states. In a computer we talk about this states are the 0 and the 1, but all depends of how we interpret that 0 and that 1. Instead we can think in up and down, white and black or any other pair of states that we think, without that have to be necessarily opposed.

The two states of a bit are represented in a computer passing or not current, in a hard disk is represented with the magnetic domains aligned to the left or to the right, in a CD is there is a hole or not, etc.

In the same way that joining 1.000 meters we have 1 kilometre, if we join 1.000 bits we have 1 kilobit (Kbit), if we join 1.000 Kbit a Megabit (Mbit). Following in the same way we have the Gigabit (Gbit), the Terabit (Tbit), the Petabit (Pbit), the Zettabit (Zbit) and finally, and by the moment, the Yottabit (Ybit).

The bit by second is the information unit used to measure the transmission speed of a medium as an ADSL connexion.

- The byte:

A byte (name invented by Waner Buchholz in 1957) are 8 bits, and this is so because is the minimum unit information with the most personal computer can work. To any machine that work with the binary numbering system, is more comfortable and optimum work with quantities that are multiples of power of 2, in this case 23, at the same way, to any human that works with the decimal numbering system, is more easy multiply and divide by powers of 10.

The byte is information unit used to measure the quantity of information that can store a device.

- Megabyte y Mebibyte:

Before of the norm published by the International Electrotechnical Commission (IEC) in 1994 the Megabyte was 1.024 bytes (1.024=210). Is that to say, to know how many bytes had a diskette of 1,44 MB we had to multiply two times by 1.024 (not by 1.000). This nomenclature also was used in all operating system to show the quantity of information stored in the files and the RAM memory.

After, will appear the CD that followed using the nomenclature correctly, but in some hard disk will began to calculate the quantity of Megabytes dividing incorrectly two times by 1.000, the quantity of bytes, getting a greater value of Megabytes than the really had, being more the difference when more capacity had the hard disk.

As the majority of users didn't realize about it, this swindle rapidly was extended to all the store devices, the DVD, Blu-Ray, Pen-Drives, etc. For instance a DVD of 4,7 GB, really have (4,7 * 109)/230= 4,377 GB (according to the nomenclature prior to the IEC), a Blu-Ray of double side of 50 GB have really (50 * 109)/230= 46,566 GB, and a hard disk of 1 TB have (1*1012)/240= 0,909 TB. In this last case we have 92,67 GB less than we expected.

To avoid more confusion comes to the rescue a norm published by the (IEC) in 1994, saying that since then a Megabyte was 1.000 kilobytes and a Mebibyte was 1.024 kibibytes. Is that to say, that the before was called Mega now is Mebi, and the magnitude called Mega now is another thing that have been invented by the manufacturers to swindle the users. The new prefixes are:

Kibibyte (KiB), Mebibyte (MiB), Gibibyte (GiB), Tebibyte (TiB), Pebibyte (PiB), Exbibyte (EiB), Zebibyte (ZiB), Yobibyte (YiB).

To finish messing completely all, with this terrible norm, appears other unit for the bits, the Mebibit (Mibit) that it is equivalent to 1.024 kibibits, although in this case the old nomenclature is kept and a Megabit (Mbit) remains being 1.000 Kilobits (1.000).

- The swindle of the Megas:

When an Internet provider sell us a line of 20 Megs without saying more, he do it knowing that the user don't know that the 20 Megs are really 20 Megabits/s. The provider hide deliberately the information of the magnitude used because he knows that the only information unit that know the majority of users is the one that shows their operating system when they look how much space fill an archive (that will be Mebibtys or Megabytes depending of the application or the operating system, although really allways are talking about the same).

To know the equivalence of these 20 Megabits/s to hard disk space we have to do this operation (20 * (106)/8)/220= 2,38 MiB/s that is quite less.

- Moral:

The informatics illiteracy implies that the enterprises can manipulate the people, for that is important that always you be well informed visiting Computable Minds.

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