1. Bits and bytes
September 19, 2017

2. Units of measure Recall: Eight bits of data are called a byte.
A single character of ASCII text requires one byte.
How many bytes would be needed to store “hello” in a plain text document?
Plain text document (.txt): 5 bytes
Word document (.docx): 21,969 bytes
Why the difference??

3. Bytes Kilobyte (KB): about 1,000 bytes (103)
Megabyte (MB): about 1,000 KB, or 1 million (106) bytes
A 3.5” floppy disk has a capacity of 1.44 MB.
Gigabyte (GB): about 1,000 MB, or 1 billion (109) bytes
A DVD disk has a capacity of 4.7 GB.
Terabyte (TB): about 1,000 GB, or 1 trillion (1012) bytes

4. Why “about”?
Since all of these measures are based on bits, which are in turn based on powers of 2, there is a school of thought that says 1 KB = 210 bytes.
210 = 1024 bytes
Similarly, 1 MB = 220 bytes = 1,048,576 (10242) bytes
1 GB = 230 bytes = 1,073,741,824 (10243) bytes…
The terms “kibibyte,” “mebibyte,” “gibibyte,” and “tebibyte” have been introduced as a means of referring to this powers-of-2 interpretation.
For our purposes, stick with the powers-of-10 interpretation.

5. Unit conversions Simple math: If you have n bytes, you have n/1000 KB.
23,000 bytes = 23 KB.
Similarly, if you have n KB, you have n/1000 MB.
45,400 KB = 45.4 MB.
Et cetera.

6. Unit conversions 2,000,000 bytes is about how many MB?
23,000 KB is about how many MB?
500 KB is about how many MB?
4,000,000,000 bytes is about how many GB?
Suppose you have several 5 MB .jpg images. How many would fit on a 16 GB flash drive?