With 8 bits, we have 28= 256 possibilities (each bit can be zero or one, and the possibilities multiply together). We call 8 bits a byte. The very common ASCII system makes each letter of the alphabet, both capital and small (plus punctuation and some other symbols) correspond to a number from 0 to 255 (for example a=97, b= 98 and so on), so one letter can be expressed with one byte. Show Thus the word "Shannon" takes 7 bytes. A page of a book (with 50 characters per line, 50 lines per page) takes 2,500 bytes, so a 400 page book takes 1,000,000 bytes. As with metres and kilometres, we need some new units, or we'd need a lot of zeroes! Hence we write that a page is approximately 2.5KB, and a book is approximately 1 MB (something strange happens here in that KB ("kilobyte") = 1,024 = 210 bytes, not 1000 as you might expect). It's easiest to keep track of things with powers of 2 like this. The next largest unit is 1MB ("megabyte") = 1,048,576 = 220 bytes, and then 1GB ("gigabyte") = 230 bytes.  Bits and bytes Computers often represent a pixel of colour with 3 bytes. This is like mixing paint - the amount of red in the mixture varies from 0 to 255, the amount of green varies from 0 to 255, the amount of blue from 0 to 255. A computer monitor showing As for a movie, we need A CD-R can typically store about 700MB, a DVD can store about 4GB. It's clear we have to do something clever (that is, data compression) to fit a movie on a disc. 32 space 33 ! 34 " 35 # 36 $ 37 % 38 & 39 ' 40 ( 41 ) 42 * 43 + 44 , 45 - 46 . 47 / 48 0 49 1 50 2 51 3 52 4 53 5 54 6 55 7 56 8 57 9 58 : 59 ; 60 < 61 = 62 > 63 ? 64 @ 65 A 66 B 67 C 68 D 69 E 70 F 71 G 72 H 73 I 74 J 75 K 76 L 77 M 78 N 79 O 80 P 81 Q 82 R 83 S 84 T 85 U 86 V 87 W 88 X 89 Y 90 Z 91 [ 92 \ 93 ] 94 ^ 95 _ 96 ` 97 a
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Data is often expressed in bytes, which are composed of eight binary digits. Bytes are used to represent all sorts of data, including letters, numbers and symbols. Each byte is made up of a string of bits that must be used in the larger unit for applications. This page provides tables that include information about how many bytes are required to store data for various information objects or purposes. It also summarizes a number of facts about how much information exists in the world. How many bytes for anything?The following table shows information objects that range in size from 1 bit to exabytes (EB) and zettabytes (ZB). Much of the information originally came from calculations done by Roy Williams on his "Powers of Ten," webpage, which is now expired. Data also came from the University of California at Berkeley, which derived some of its data from the Williams article. In a more recent update, data was added from Bryn Mawr College, Computer Hope, GreenNet, IDC and BBC Science. Information object How many bytes? A binary decision 1 bit A single text character 1 or 2 bytes A typical text word 10 to 20 bytes A line of text 70 bytes Two or three paragraphs of text 1 kilobyte (KB) A page of plain text 2 KB A short email 5 KB A simple five-page word-processor document 30 KB A low-resolution photograph 100 KB A short novel 1 megabyte (MB) The average size of a webpage 2 MB A high-resolution photograph 2 to 3 MB A three-minute MP3 audio 3 to 5 MB The complete works of Shakespeare 5 MB One meter of shelved books 100 MB The contents of a CD-ROM 700 MB A pickup truck filled with books 1 gigabyte (GB) The contents of a single-layer DVD 4.7 GB The collected works of Beethoven 20 GB A library floor of academic journals 100 GB 50,000 trees made into paper and printed 1 terabyte (TB) An academic research library 2 TB The print collections of the U.S. Library of Congress 15 TB Total archived data for the Hubble Space Telescope 150 TB Total data the National Centers for Environmental Information managed 30 petabytes (PB) Total data Amazon, Facebook, Google and Microsoft stored 1.2 EB All words ever spoken by human beings 5 EB The installed base of storage capacity in 2020 6.7 ZB Total data created or replicated in 2020 64.2 ZB How many bytes for a website?The following table contains information from the Page Weight report published by HTTP Archive, an open source project. Information object How many bytes? The average transfer size of all HTML documents requested by a webpage 29.7 KB The average transfer size of all external stylesheets requested by a webpage 74.2 KB The average transfer size of all fonts requested by a webpage 141.1 KB The average transfer size of all external scripts requested by a webpage 505.6 KB The average transfer size of all external images requested by a webpage 979.5 KB The average transfer size of all resources requested by a webpage 2.2 MB The average transfer size of all videos requested by a webpage 2.5 MB A downloadable file, program or driver File sizes vary; users are sometimes notified of a file's size before downloading it. How much information exists?The following table includes information published by FinancesOnline, a software discovery and research platform. FinancesOnline gathered the information from a wide range of other sources. How many bits are needed for the alphabet?We call 8 bits a byte. The very common ASCII system makes each letter of the alphabet, both capital and small (plus punctuation and some other symbols) correspond to a number from 0 to 255 (for example a=97, b= 98 and so on), so one letter can be expressed with one byte. Thus the word "Shannon" takes 7 bytes.
How many bits would be needed to count all of the students in class?How many bits would you need to count all of the students in class today? If you have 12 students in class you will need 4 bits. Each time we add another bit, what happens to the amount of numbers we can make? What are the similarities and differences between the binary and decimal systems?
How many bits would be needed to count 30 students?30 in binary is 11110. Unlike the decimal number system where we use the digits 0 to 9 to represent a number, in a binary system, we use only 2 digits that are 0 and 1 (bits). We have used 5 bits to represent 30 in binary.
How many bits would be needed to count 15 students?For example, the number 15 can be represented in 4 bits, but 16 requires 5 bits.
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