Editing RT-11 (section)

===Human interface===
[[File:RT-11 help.jpg|thumb|The end of the {{mono|HELP}} command output from [[:en:RT-11|RT-11SJ]] displayed on a [[:en:VT100|VT100]].]]
Users generally operated RT-11 via a [[Teleprinter|printing terminal]] or a [[Computer terminal|video terminal]], originally via a strap-selectable current-loop (for conventional teletypes) or via an [[RS-232]] (later [[EIA-422|RS-422]] as well) interface on one of the CPU cards; DEC also supported the VT11 and VS60 graphics display devices ([[vector graphics]] [[Computer display|terminal]]s with a graphic character generator for displaying text, and a [[light pen]] for graphical input). A third-party favorite was the [[Tektronix 4010]] family.

The Keyboard Monitor (KMON) interpreted commands issued by the user and would invoke various utilities with Command String Interpreter (CSI) forms of the commands. 
RT-11 command language had many features (such as commands and device names) that can be found later in the [[DOS]] line of operating systems which heavily borrowed from RT-11. The CSI form expected input and output [[filename]]s and [[Command-line argument|options]] ('switches' on RT-11) in a precise order and syntax. The command-line switches were separated by a slash (<code>/</code>) rather than the dash (<code>-</code>) used in [[Unix-like]] operating systems. All commands had a full form and a short one to which they could be contracted. For example, the RENAME command could be contracted to [[ren (command)|REN]].

Batch files and the batch processor could be used to issue a series of commands with some rudimentary [[control flow]]. Batch files had the [[filename extension|extension]] .BAT.

In later releases of RT-11, it was possible to invoke a series of commands using a .COM command file, but they would be executed in sequence with no flow control. Even later, it was possible to execute a series of commands with great control through use of the Indirect Command File Processor (IND), which took .CMD control files as input.

Files with the extension .SAV were a sort of executable. They were known as "save files" because the RT-11 SAVE command could be used to save the contents of memory to a disk file which could be loaded and executed at a later time, allowing any session to be saved.

The SAVE command, along with GET, [[start (command)|START]], REENTER, EXAMINE and DEPOSIT were basic commands implemented in the KMON. Some commands and utilities were later borrowed in the [[DOS]] line of operating systems. These commands include [[dir (command)|DIR]], [[copy (command)|COPY]], [[ren (command)|RENAME]], [[assign (command)|ASSIGN]], [[cls (command)|CLS]], [[del (command)|DELETE]], [[TYPE (DOS command)|TYPE]], [[help (command)|HELP]] and others. The [[format (command)|FORMAT]] command was used for physical disk formatting, although it was not capable of creating file system, for which purpose the INIT command was used (analogue of DOS command FORMAT /Q). Most commands supported using [[Wildcard character|wildcards]] in file names.

Physical device names were specified in the form 'dd{n}:' where 'dd' was a two-character alphabetic device name and the optional 'n' was the unit number (0–7). When the unit number was omitted, unit 0 was assumed. For example, TT: referred to the console terminal, LP: (or LP0:) referred to the parallel line printer, and DX0:, DY1:, DL4: referred to disk volumes (RX01 unit 0, RX02 unit 1, RL01 or RL02 unit 4, respectively). Logical device names consisted of 1–3 alphanumeric characters and were used in the place of a physical device name. This was accomplished using the <code>ASSIGN</code> command. For example, one might issue <code>ASSIGN DL0 ABC</code> which would cause all future references to 'ABC:' to map to 'DL0:'. Reserved logical name DK: referred to the current default device. If a device was not included in a file specification, DK: was assumed. Reserved logical name SY: referred to the system device (the device from which the system had been booted).

Later versions of RT-11 allowed specification of up to 64 units (0–77 octal) for certain devices, but the device name was still limited to three alphanumeric characters. This feature was enabled through a SYSGEN selection, and only applied to the DU and LD device handlers. In these two cases, the device name form became 'dnn:' where 'd' was 'D' for the DU device and 'L' for the LD device, and 'nn' was 00–77(octal).