Bits, Bytes, and Binary
A common question clients often ask is how long should it take to download a file or transfer data? A quick review of data measurements will help answer the question.
At the physical level, your computer hardware sees data as either yes or no, voltage or no voltage, marked or not marked, on or off, and so on. These two options, or binary choices, are represented by a 1 or a 0. We refer to this as binary since there are only two possible choices. A single value, either a 1 or a 0 is referred to as a bit. With only 2 options, a single bit is a small amount of data. We get a more useful amount of data by grouping 8 bits together to form a byte. A byte of data, or 8 bits, has 2^8 options (256) and is much more useful for storing data.
Kilo, Mega, and Giga – not quite 1000
In the metric system that we all know, Kilo means 1000 times the base unit. This naming structure is used for computers because most people are familiar with it, and it is close to correct. The slight error comes from the fact that for data, computes use a binary system, rather than a decimal system for counting. In binary, Kilo means 1024 or 2^10. So a Kilobyte is actually 1024 bytes. This seemingly small difference really adds up. For example, just how many bytes does a 120 Gigabyte backup hold?
120 Gigabytes x 1024 = 122,880 Megabytes
122,880 Megabytes x 1024 = 125,829,120 Kilobytes
125,829,120 Kilobytes x 1024 = 128,849,018,880 Bytes
As we can see this little difference really adds up.
120 Gigabytes = 128 Billion bytes, not 120 Billion bytes.
Proper Abbreviation of Bits and Bytes Prevents Confusion
When we write out the entire word, bit or byte, it is clear what we are talking about. When we abbreviate, the meaning can get lost if we are not careful. The convention is for bits, use a lower case b; for bytes, use a capital B. Most often this confusion occurs when talking about files or data connections. A file might be 2 Megabytes, or 2 MB, and an internet connection might be 3 Megabits per second, or 3 Mbps. Sadly, this convention is not followed all the time, usually because people just don’t think it matters. A good rule of thumb is that data storage is usually bytes, and transfer rates are usually bits, but not always.
How to use Bits, Bytes, and Binary for Everyday Applications
How long should it take to download a 3 Meg file on a 384 K high speed internet connection? With the information above, we should be able to answer the question. Since we don’t know if we are taking about bits or bytes from the question, we will assume that the file is in bytes, and the internet connection is in bits, since this is usually the case. If we convert the 3 Megabyte file into Kilobits to match the internet connection we will have a common unit that allows us to divide and find out how much time.
3 Megabytes x 8 = 24 Megabits
24 Megabits x 1024 = 24,576 Kilobits
24,576 Kb / 384 Kbps = 64 seconds
So we now know that the file should take just over a minute to download. By using the same techniques we can also convert our internet speed from 384 Kbps, to a slightly easier to work with 2.8 Megabytes per minute.
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