iDSKY

The Basics

The user interface of the Apollo Guidance Computer was the "Display and Keyboard," which was abbreviated to DSKY, and pronounced "dis-key". The Command Module had two DSKYs - one on the Main Display Console, and one at the navigation station. The Lunar Module had a single DSKY.

Display

The display consists of two major parts: the alert annunciators on the left, and the numeric display on the right. The alert annunicators are used to highlight various conditions:

Legend	Meaning
UPLINK ACTY	Data is being uplinked to the AGC from Mission Control.
NO ATT	The Inertial Measurement Unit (IMU) is not in a state to provide useful attitude reference data. It needs to be initialized.
STBY	The AGC is in low-power standby mode. This state is entered by executing PROG 06; it can be exited by pressing the PRO key.
KEY REL	The AGC has data to display, but the DSKY is currently being used by a crewmember for another task. When that task is completed, the crewmember should press KEY REL to allow the pending data to be displayed.
OPR ERR	A keystroke combination was entered that was not valid. For example the user tried to load data into a noun that is not permitted to be loaded.
TEMP	The temperature of the IMU is outside its normal operating limits.
GIMBAL LOCK	This is a warning that the middle gimbal of the IMU is within 15° of entering a configuration that will prevent free gimbaling. If Gimbal Lock actually occurs, NO ATT will be illuminated.
PROG	An internal hardware or software error was detected. The RSET key can be used to acknowledge the alert and reset the PROG annunciator. V05N09E can be used to display more information on the specific error.
RESTART	An error has occurred that required an automatic restart of the executing program. As with the PROG alert, RSET will turn off the RESTART annunciator.
TRACKER	An failure has occurred in the optics subsystem electronics.
ALT	(LM only) Flashing: Landing radar altitude reasonability test failed. Steady: Landing radar range data not good.
VEL	(LM only) Flashing: Landing radar velocity reasonability test failed. Steady: Landing radar velocity data not good.
PRIO DISP	(LM only) A priority display from P20 is pending.
NO DAP	(LM only) Indicates that the Digital Autopilot is not controlling the spacecraft attitude.
Note: These annunciators were slightly different between the CM and the LM DSKYs. Also, they occasionally would be changed or rearranged on different flights. What is shown in iDSKY is a typical CM arrangement.

The numeric part of the display consists of three 2-digit displays that indicate the currently active Program, Verb and Noun; and three signed 5-digit registers. If a sign a present, this indicates that decimal data is being displayed; the absence of a sign indicates that data is displayed in octal.

Keyboard

This is the primary input method. Additional input controls are available at the navigation station.

Key	Meaning
+ and –	Indicates that the following data entry is decimal. Decimal data entry requires that five digits must be entered (i.e. leading zeroes are required).
VERB	Used to blank the Verb code and initiate Verb entry.
NOUN	Used to blank the Noun code and initiate Noun entry.
CLR	Clears the register currently being loaded. Subsequent presses will clear previously loaded registers.
PRO	Used to indicate that the currently running program should proceed without any further input.
KEY REL	Releases the display for internal use.
ENTR	Terminates data entry.
RSET	Clears the OPR ERR annunciator.