Why are network cables rated in bits, when files are stored as bytes?

Question

Cat5 - 100Mbps
Floppy disk - 1.44MB

Answer 1

Usually, serial devices are rated in bits per second. Serial devices transfer data a bit at a time, and the data doesn't necessarily have an 8 bit frame. For example, with those fax/phone modems, PCs typically used 8 bit data, 1 stop bit, no parity bit, while Macs used 7 bit data, 1 stop bit, no parity bit. Also, those modems were rated using the 'baud' term (e.g. 14400 baud).

Answer 2

It's all binary code. A bit is either a 1 or a 0. For cables, the bitrate is the standard of measure. For storage of data, a computer processes bytes (8 bits). Nowadays, with multiprocessors, a computer can process 32 bits at once, or 4 bytes. So, one refers to the rate that 1's or 0's are flowing along a wire, the other refers to data storage. You could say a floppy holds 8 times 1.44 MB bits of data, but it's more economical to refer to storage size in bytes.

Answer 3

Because the actual data sent may not be in complete bytes.

When you send the text "Hello" (5 bytes), it may take more than that 5 byte information over the network. Each layer of protocol adds their header and trailer info around your message. This may include your address, routing info, error detection/correction codes, framing flags, etc (depending on what protocols are used). Your message may also be encrypted into something not recognizable. At the end, it may end up like 151 bits, for example.

Counting bytes on a communication wire is just not practical.

Answer 4

Back a hundred years ago :-), communications between computers were rated in bits because that was what could be moved across the line reliably, i.e., the number of discrete conditions or events per second. As things sped up, the measuring mechanism stayed. Ditto for the storage nomenclature.

IBM came out with the first storage device for computers - it was 5mb and the size of two? refrigators. They decided on the sizing and that is all she wrote.

Interesting thought on this line of thinking - how long before mb's lose their meaning as well? gb's are fairly standard and I imagine in a few years tb's will be.

Answer 5

Bandwidth.
Cable can only (generally) carry data 1 bit at a time in serial fashion, therefore the capacity of the cable is expressed in bits/sec. It's for the same reason that data lines are expressed in bits/sec. They also send and recieve data serially.

Answer 6

Well, first of all, everything digital is ultimatly stored in bits, which is either a 1, or a 0. Although I don't know the exact reason, I believe it is so you can measure the exact amount of data transfered, including binaries.

Answer 7

The truth is, it's a marketing trick. 100 megabits sounds faster than 12.5 megabytes, so it sounds like you're getting a better deal. Rental places quote by the week instead of the month to make the payments sound less. Same theory in reverse.