The interactive processor

Interactive command processor

Launched with no file, each command drops into an interactive command processor — a small, FORTRAN-focused descendant of the TOPS-10 . prompt. It works on whole source files (F66 has no incremental-execution model), except for IMMEDIATE mode. The command set is the same for all three commands; only the starting dialect differs, and SET STD flips it.

f66> RUN prog.for             # compile + run a file        (alias EXECUTE)
f66> CHECK prog.for           # parse + list diagnostics, no run  (alias COMPILE)
f66> LOAD prog.for            # parse a file into the session
f10> START                    # run the loaded program; RESET drops it
f10> SET STD fortran10        # switch dialect / TARGET / PROGRAM between runs
f10> SET TARGET pdp10
f10> SHOW /OUT/               # inspect a COMMON block after a run; SHOW = settings
f10> !ls                      # run a host shell command
f10> @script.mon              # run commands from a file
f10> HELP                     # the command list
f10> EXIT                     # quit                          (alias QUIT)

Debugging

The command processor carries a per-statement debugger/profiler (off by default — a plain RUN pays nothing):

f66> BREAK 7                  # breakpoint at line 7 (no arg = list); UNBREAK to remove
f66> STEP                     # the next RUN stops at the first statement
f66> RUN prog.for             # at a (dbg) prompt: step / next / cont, where, p <expr>
f66> TRACE on                 # echo each statement as it runs
f66> PROFILE on               # per-line execution counts; PROFILE (no arg) shows the report
f66> COVERAGE                 # which lines the last run reached

At the (dbg) prompt, typing a name inspects it (the engine's own evaluator); a bare command word wins over a same-named variable, so use p <expr> / =<expr> to force inspection.

IMMEDIATE (a REPL)

f66> IMMEDIATE                # alias REPL — interactive FORTRAN
*> I = 6 * 7                  # statements run as you type
*> TYPE *, I                  # 42
*> 2 + 3 * 4                  # a bare expression is evaluated and printed -> 14

A DO loop is collected across lines and run as a block; declarations accumulate in a persistent session. COMMON/EQUIVALENCE/NAMELIST are out of scope for immediate mode — put them in a file and LOAD it.

The command processor's ! shell escape and @file scripts run with your shell's privileges and are not reachable from a running FORTRAN program. Treat a command script as trusted input; don't wire the command processor to an untrusted source.