This bc was written by Gavinhoward.
These extensions are in OpenBSD bc, but not in POSIX:
- The -e and f options.
- Global stacks.
- # Line comments.
- Relational operators (== <= >= != < >) in any expression, not only in 'if', 'while', or 'for'.
- Boolean operators (! && ||).
- else branch of an 'if' statement.
- print statement, with escapes like '\n'.
- Special variable last, also known as . (a single dot).
- Scientific and engineering notation.
- A pseudo-random number generator.
- A way to get user input (read()).
And many more.