See also gnu

bc [ -lwsqv ] [long-options] [ file ... ]

bc supports arbitrary precision numbers.
Executes files on the command line, then reads from the standard input and processes interactively.

Sets scale=20 loads math library.
Give warnings for extensions to POSIX bc.
Do not print the welcome.
Display version number, short copyright and quits, see warranty.
bc 1.06
Copyright 1991-1994, 1997, 1998, 2000 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.  

In .profile set up alias bc='/usr/bin/bc -q ~/.bin/bc.ini' and
create ~/.bin/bc.ini containing :scale=2
then echo 5/6|bc will output .83