HACTRN basics

HACTRN is the first program the user interacts with when having logged in. It's another name for the debugger DDT, which is used to start and control programs, and to manipulate the file system. It's similar to, but much more powerful than the non-timesharing DDT which is used to start and debug ITS itself.

Many HACTRN commands come in two versions: a colon command and a DDT command. Colon commands start with a colon, followed by a name. DDT commands are control characters, or have an Altmode prefix, or both. Colon commands may be easier to learn and remember in the beginning, but DDT commands have stronger fluidity in use and have the same user experience as TECO and EMACS. Beginners are encouraged to use the DDT commands from the start.

A running programs is called a job. DDT can manage up to eight jobs. Each job may in turn have subjobs. You can usually suspend the current job by typing ^Z, but it will remain waiting in the background.

HACTRN remembers the last file name you typed to it; this is called file name defaults. When you type a file name, missing components will be filled in from the defaults, and then defaults are updated.

Some important HACTRN commands are:

DDT command	Colon command	Meaning
foo$U	:LOGIN foo	Log in as user foo.
$$U	:LOGOUT	Log out.
	:HELP	Brief help.
	:?	List all colon commands.
^F	:LISTF	List files in current directory.
foo^F	:LISTF foo	List files in foo, which may be a device or directory.
foo$$^S	:CWD foo	Change current directory to foo.
^Rfoo	:TYPE foo	Print the file foo on the display.
foo^K	:foo	Start program named foo.
^Z		Suspend current job.
$$V	:LISTJ	List jobs.
$J	:JOB	Switch to the next job in the list.
foo$J	:JOB foo	Switch to the job named foo.
$^X.	:KILL	Kill current job.
foo$^X		Kill job named foo.
$P	:CONTINUE	Resume current job.
^P	:PROCED	Run current job in the background.