A programming language for the HP48 calculator. The RPL language, which includes a transparent compiler, is visible to the user and looks like:

  1 10 FOR X
    X SIN   NEXT
System RPL, or SysRPL, is a strict superset of User RPL and includes far more functionality than User RPL allows. The above program, viewed in SysRPL terms:
  %1 %10 xFOR ' ID X
    ::     ID X xSIN    ;
However, the HP48 calculator does not include a compiler for SysRPL. Despite this fact, enterprising souls produced several and it is entirely possible to program SysRPL and even assembly on the HP48.