bc: the scientific calculator
bc is a command-line scientific calculator. It is shipped with most Unix-like systems.
Important variables
scale
Due to bc behaves like an arbitrary-precision calculator, its precision must be set. scale is the special variable that controls the precision; its default value is 0. The command scale=4 to set it to 4 and scale output the current setting.
Comparisons
dc is the predecessor to bc, but it uses a Polish (prefix) notation. bc used to be built on top of dc but it was later rewritten and became independent.
hoc can be considered as a successor to bc that developed as a part of the Plan 9 project. From a calculation perspective, hoc is like bc but it is more convenient than bc because behaves more like a modern programming language (e.g., use 1.2E5 instead of 1.2*10^5 for scientific representation of ); but it is unfortunately usually not built into Unix-like distributions and is less accessible.
Installations
In Windows, bc comes with scoop package unxutils.
Additional notes
Lorinda Cherry, a female developer who worked with Robert Morris to develop bc in Bell labs, passed away in Feb. 2022.