Students in CS&E 141 should use the
following format for writing up "Back of the Envelope Calculations"
(abbreviated "BotEC").
BotEC's have:
Formula(s) that provide a roadmap to the
upcoming calculations. The formula should include names for
any quantity that will be estimated, and should give units
of measurement (in parentheses). Conversion factors (e.g. bits/Byte)
can appear without a name.
Estimates of the quantities appearing
in the formula. There should be a very brief justification of the
estimate if it isn't obvious. You should use "wiggley equal signs"
to indicate approximations.
Calculations in which the estimates and
known facts are substituted into the formula.
Example: Bandwidth needed for full screen video
Formula
Bandwidth (Bytes/sec) = ScreenSize(dots/image) x RefreshRate (images/sec)
x Information (Bytes/dot)
Estimates
ScreenSize ~= 1,000,000 dots/image (estimating a 1000x1000 screen)
RefreshRate ~= 30 images/second (so eye won't see flicker)
Information = 3 Bytes/dot (one Byte each for R, G, B)
Calculation
Bandwidth ~= 10^6 dots/image x 30 images/sec x 3 Bytes/dot = 90x10^6 Bytes/sec
~= 100 MByte/sec