Editor functions (ed.*c)
ed.chared.c:	Editor basic function implementation. (Motion/Search etc.)
ed.defns.c:	Editor command tables.
ed.init.c:	Editor initialization. Tty/signal setup.
ed.term.c:	Tty driver dependent initialization portion.
ed.inputl.c:	Editor input, editor command parser, and dispatcher.
ed.refresh.c:	Editor refreshing. How to change the old line to the current.
ed.screen.c:	Termcap related functions.
ed.xmap.c:	Key macro handling.

glob.c:		The 4.4BSD globbing library function.

Shell functions (sh*.c). All these files are from csh.
sh.c:		Initialization, command loop and script handling.
sh.char.c:	Character classification tables.
sh.dir.c:	Directory handling (cd, pushd, popd, dirs). Initialization
		and symbolic link resolution.
sh.dol.c:	Input line processor. Dollar/History expansion.
sh.err.c:	Error handling routines and table.
sh.exec.c:	Command execution (searching and executing commands)
		also which builtin.
sh.exp.c:	Expression evaluation.
sh.file.c:	Old csh file completion. Not used in tcsh.
sh.func.c:	Csh builtin functions.
sh.glob.c:	Wildcard matching. Also backquote, brace and tilde evaluation.
sh.hist.c:	History book-keeping.
sh.init.c:	Signal and builtin tables.
sh.lex.c:	Lexical analyzer.
sh.misc.c:	General purpose utilities.
sh.parse.c:	Parser. Not really a parser. Recognizes sequences of tokens
		as builtins.
sh.print.c:	Primitive output (basic character output).
sh.proc.c:	Job handling. Adds new children to the job list.
		Catches dead children and removes them from the job list.
		Builtins for stopping/killing/ and moving jobs to the background
		foreground.
sh.sem.c:	Job spawning (nice and time are handled here too) and I/O
		redirection.
sh.set.c:	Variable setting.
sh.time.c:	Time keeping and reporting.

Tcsh additions (tc*.c)
tc.alloc.c:	Malloc/Free
tc.bind.c:	Key binding user access functions.
tc.const.c:	Short String constants.
tc.disc.c:	Line discipline set/clear.
tc.func.c:	Tcsh additional builtins.
tc.os.c:	OS dependencies/system call emulations.
tc.printf.c:	Stdio like printf using the routines in sh.print.c
tc.prompt.c:	Prompt expansion.
tc.sched.c:	Scheduling commands handling.
tc.sig.c:	Signal emulation for SVR2, SVR1 and V5.
tc.str.c:	<string.h> for short strings.
tc.vers.c:	HOSTTYPE and $version
tc.who.c:	Watch variable handling.

Spelling, listing, and completion (tw*.c)
tw.help.c:	Display help for a command by catting a file.
tw.init.c:	Initialization and some utilities.
tw.parse.c:	All the listing and completion. Tries to tokenize the line
		and figure out where the word(s) started and if they were
		commands or not. Then it applies the requested function to
		the word fragment.
tw.spell.c:	String spelling correction.
tw.comp.c:	File completion builtin

OS/Dependent files
mi.termios.c:	Minix termios emulation
mi.varargs.h:	Minix varargs
mi.wait.h:	Minix wait.
ma.setp.c:	MACH's setpath() library function
atp.termcap.c:  Termcap routines for vmsposix