Bits, Bytes

Date: 04/28/2003 at 08:13:37
From: Rami
Subject: Maths

A Web page of 10 megabytes is being retrieved from a Web server. What 
is the time to transfer the page over a modem operating at 28.8kbps?

According to my professor we have to divide something by 8.

Date: 04/28/2003 at 09:23:28
From: Doctor Edwin
Subject: Re: Maths

Hi, Rami.

This is not really a mathematics question; it's really about the units 
used to measure size and capacity in computer equipment.

The basic unit of data in computing is one bit - a one or a zero. Bits 
are almost always used in chunks, and the smallest chunk is usually a 
byte, or 8 bits. Bit is abbreviated with a lower-case b, and byte is 
abbreviated with an upper-case B.

When we measure the size of a file, we typically do so in bytes (or 
megabytes).

Network and dialup connection speeds are generally measured in bits 
per second, abbreviated with a lower-case b.

So your file is 10MB (Megabytes) or 80 Mb (megabits), while your 
connection speed is 28.8 kbps (kilobits per second).

One other thing: In computing, kilo and mega don't exactly mean 1,000 
and 1,000,000. Almost always, kilo means a "binary thousand" or 1024 
(2^10). So a megabyte is 2^20, or 1024^2.

So your file is actually 10 * 1024 * 1024 * 8 bits. 

Hope this helps. Write back if you have any more questions.

- Doctor Edwin, The Math Forum
  http://mathforum.org/dr.math/