In APL, expressions are evaluated based on a stack-based pseudo-machine that processes its internal operations in double precision (64-bit / C Double) floating-point numbers. The opcodes that apply to this pseudo-machine, as well as opcodes that can be used individually to specify data elements, are collectively called GetVar codes. The GetVar codes are described in the following table.
| GetVar Code | Description |
| GETVAR_END (0) | Control. Marks the end of a GetVar expression. The value of the expression is the value at the top of the stack. |
| GETVAR_EXPRESSION (1) | Control. Marks the beginning of an expression that is expressed with multiple GetVar codes. GetVar codes, until the next GETVAR_END, are part of the expression. |
| GETVAR_I8 (2) | Operand. Next byte is an 8-bit signed integer constant. |
| GETVAR_I16 (3) | Operand. Next 2 bytes are a 16-bit signed integer constant. |
| GETVAR_I32 (4) | Operand. Next 4 bytes are a 32-bit signed integer constant. |
| GETVAR_FPVAL (5) | Operand. Next 8 bytes are a double precision floating-point constant. |
| GETVAR_APL_VAR (7) | Operand. Next 4 bytes are 32-bit offset of an APL user variable. |
| GETVAR_FS_VAR (8) | Operand. Next 2 bytes are 16-bit token number of a Flight Simulator variable. See the table at the end of this topic for token number values for Flight Simulator variables. |
| GETVAR_PLUS (9) | Binary operator. Pop two values from the stack and push the sum. |
| GETVAR_MINUS (10) | Binary operator. Pop A from stack. Pop B from stack. Push B–A. |
| GETVAR_TIMES (11) | Binary operator. Pop two values from stack and push the product. |
| GETVAR_DIVIDE (12) | Binary operator. Pop A from stack. Pop B from stack. Push B/A. |
| GETVAR_IDIV (13) | Binary operator. Pop A from stack. Pop B from stack. Push int(int(B)/int(A)). |
| GETVAR_IREM (14) | Binary operator. Pop A from stack. Pop B from stack. Push B MOD A. |
| GETVAR_BITWISE_AND (15) | Binary operator. Pop two values from stack and push the bitwise And. |
| GETVAR_BITWISE_OR (16) | Binary operator. Pop two values from stack and push the bitwise Or. |
| GETVAR_BITWISE_XOR (17) | Binary operator. Pop two values from stack and push the bitwise exclusive Or. |
| GETVAR_EQ (18) | Binary operator. Pop A from stack. Pop B from stack. If A=B push 1, else 0. |
| GETVAR_NE (19) | Binary operator. Pop A from stack. Pop B from stack. If A is not equal to B push 1, else 0. |
| GETVAR_LT (20) | Binary operator. Pop A from stack. Pop B from stack. If B is less than A push 1, else 0. |
| GETVAR_LE (21) | Binary operator. Pop A from stack. Pop B from stack. If B is less than or equal t A push 1, else 0. |
| GETVAR_GT (22) | Binary operator. Pop A from stack. Pop B from stack. If B is greater than A push 1, else 0. |
| GETVAR_GE (23) | Binary operator. Pop A from stack. Pop B from stack. If B is greater than or equal to A push 1, else 0. |
| GETVAR_LOGICAL_AND (24) | Binary operator. Pop two values from stack. If both values are nonzero, push 1, else 0. |
| GETVAR_LOGICAL_OR (25) | Pop two values from stack. If either value is nonzero, push 1, else 0. |
| GETVAR_LOGICAL_NOT (26) | Unary operator. Pop a value from stack. If the value is 0, push 1, else 0. |
| GETVAR_NEGATE (27) | Unary operator. Pop A from stack. Push 0–A. |
| GETVAR_INT (28) | Function. Pop A from stack. Push Int(A). |
| GETVAR_FRAC (29) | Function. Pop A from stack. Push Fract(A) (A - Int(A)). |
| GETVAR_INRANGE (30) | Function. Pop C, B, A from stack. If A is less than or equal to both B and C, push 1, else 0. |
| GETVAR_FTOM (31) | Function. Pop alt in feet, push alt in meters. |
| GETVAR_MTOF (32) | Function. Pop alt in meters, push alt in feet. |
| GETVAR_FTOC (33) | Function. Pop temp in degrees Fahrenheit, push temp in degrees Celsius. |
| GETVAR_CTOF (34) | Function. Pop temp in degrees Celsius, push temp in degrees Fahrenheit. |
| GETVAR_MBTOINHG (35) | Function. Pop press in millibars, push press in inches of mercury. |
| GETVAR_INHGTOMB (36) | Function. Pop press in inches of mercury, push press in millibars. |
| GETVAR_KMTONM (37) | Function. Pop dist in kilometers, push dist in nmiles. |
| GETVAR_NMTOKM (38) | Function. Pop dist in nmiles, push dist in kilometers. |
| GETVAR_NMTOSM (39) | Function. Pop dist in nmiles, push dist in statute miles. |
| GETVAR_SMTONM (40) | Function. Pop dist in statute miles, push dist in nmiles. |
| GETVAR_GROUND_ DIST (41) | Function. Pop lon, lat, push ground (2-D) distance from plane to lat, lon in nmiles. |
| GETVAR_AIR_DIST (42) | Function. Pop lon, lat, push air (3-D) distance from plane to lat, lon in nmiles. |
| GETVAR_RADIAL (43) | Function. Pop lon, lat, push angle from lat, lon to plane in the horizontal plane in degrees magnetic. |
| GETVAR_GLIDE_SLOPE (44) | Function. Pop lon, lat, push glideslope to lat, lon in degrees. |
| GETVAR_DEGREES (45) | Function. Pop angle, push degrees. |
| GETVAR_MINUTES (46) | Function. Pop angle, push minutes. |
| GETVAR_SECONDS (47) | Function. Pop angle, push seconds. |
| GETVAR FTF DIST (48) | Function. Pop lon2, lat2, lon1, lat1. Push distance in nmiles. |
| GETVAR INRANGE360 (49) | Function. Pop C, B, A. If the angle A is between the angles B and C, push 1 else push 0. |
The following table includes Flight Simulator variables and their respective token number values.
| Variable | Token number value |
| COM_FREQ | 0 |
| NAV1_FREQ | 1 |
| VOR_1_DME | 2 |
| VOR_1_OBS | 3 |
| NAV2_FREQ | 4 |
| VOR_2_DME | 5 |
| VOR_2_OBS | 6 |
| ADF_FREQ | 7 |
| TRANS_FREQ | 8 |
| OMARK | 9 |
| MMARK | 10 |
| IMARK | 11 |
| KEY | 12 |
| RANDOM | 13 |
| PLANE_LAT | 14 |
| PLANE_LON | 15 |
| PLANE_ALT | 16 |
| PLANE_PITCH | 17 |
| PLANE_BANK | 18 |
| PLANE_HEADING | 19 |
| SEASON | 20 |
| HOUR | 21 |
| MINUTE | 22 |
| SECOND | 23 |
| VOR_1_ACTIVE | 24 |
| VOR_1_LAT | 25 |
| VOR_1_LON | 26 |
| VOR_1_ALT | 27 |
| VOR_1_RADIAL | 28 |
| VOR_1_DME_AVAIL | 29 |
| VOR_1_LOCALIZER_AVAIL | 30 |
| VOR_1_GS_AVAIL | 31 |
| VOR_1_LOCALIZER | 32 |
| VOR_1_GLIDESLOPE | 33 |
| VOR_2_ACTIVE | 34 |
| VOR_2_LAT | 35 |
| VOR_2_LON | 36 |
| VOR_2_ALT | 37 |
| VOR_2_RADIAL | 38 |
| VOR_2_DME_AVAIL | 39 |
| ADF_ACTIVE | 40 |
| ADF_LAT | 41 |
| ADF_LON | 42 |
| ADF_ALT | 43 |
| ADF_RADIAL | 44 |
| CLOUD_LOW_ACTIVE | 45 |
| CLOUD_LOW_BASE | 46 |
| CLOUD_LOW_TOP | 47 |
| CLOUD_LOW_COVERAGE | 48 |
| CLOUD_LOW_TYPE | 49 |
| CLOUD_LOW_TURB | 50 |
| CLOUD_HIGH_ACTIVE | 51 |
| CLOUD_HIGH_BASE | 52 |
| CLOUD_HIGH_TOP | 53 |
| CLOUD_HIGH_COVERAGE | 54 |
| CLOUD_HIGH_TYPE | 55 |
| CLOUD_HIGH_TURB | 56 |
| CLOUD_THUNDER_ACTIVE | 57 |
| CLOUD_THUNDER_BASE | 58 |
| CLOUD_THUNDER_TOP | 59 |
| CLOUD_THUNDER_ | |
| COVERAGE | 60 |
| CLOUD_THUNDER_TYPE | 61 |
| CLOUD_THUNDER_TURB | 62 |
| WIND_SURF_DEPTH | 63 |
| WIND_SURF_VEL | 64 |
| WIND_SURF_DIR | 65 |
| WIND_SURF_TURB | 66 |
| WIND_SURF_TYPE | 67 |
| WIND_LOW_BOT | 68 |
| WIND_LOW_TOP | 69 |
| WIND_LOW_VEL | 70 |
| WIND_LOW_DIR | 71 |
| WIND_LOW_TURB | 72 |
| WIND_LOW_TYPE | 73 |
| WIND_MID_BOT | 74 |
| WIND_MID_TOP | 75 |
| WIND_MID_VEL | 76 |
| WIND_MID_DIR | 77 |
| WIND_MID_TURB | 78 |
| WIND_MID_TYPE | 79 |
| WIND_UP_BOT | 80 |
| WIND_UP_TOP | 81 |
| WIND_UP_VEL | 82 |
| WIND_UP_DIR | 83 |
| WIND_UP_TURB | 84 |
| WIND_UP_TYPE | 85 |
| TEMPERATURE_SURFACE_ | |
| ALT | 86 |
| TEMPERATURE_SURFACE_ | |
| TEMP | 87 |
| TEMPERATURE_LOW_ALT | 88 |
| TEMPERATURE_LOW_TEMP | 89 |
| TEMPERATURE_MID_ALT | 90 |
| TEMPERATURE_MID_TEMP | 91 |
| TEMPERATURE_HIGH_ALT | 92 |
| TEMPERATURE_HIGH_TEMP | 93 |
| BAROMETRIC_PRESSURE | 94 |
| BAROMETRIC_DRIFT | 95 |
| SLEW_SYSTEM_ACTIVE | 96 |
| STALL_WARNING | 97 |
| OVERSPEED_WARNING | 98 |
| PARKING_BRAKES | 99 |
| FLAPS_LEFT_POSITION | 100 |
| FLAPS_RIGHT_POSITION | 101 |
| YOKE_X_POSITION | 102 |
| YOKE_Y_POSITION | 103 |
| RUDDER_PEDAL_POSITION | 104 |
| ELEVATOR_TRIM_POSITION | 105 |
| BRAKE_LEFT_POSITION | 106 |
| BRAKE_RIGHT_POSITION | 107 |
| GEAR_1_POSITION | 108 |
| GEAR_2_POSITION | 109 |
| GEAR_3_POSITION | 110 |
| LEFT_MAIN_FUEL_LEVEL | 111 |
| RIGHT_MAIN_FUEL_LEVEL | 112 |
| LEFT_AUX_FUEL_LEVEL | 113 |
| RIGHT_AUX_FUEL_LEVEL | 114 |
| GROUND_ALTITUDE | 115 |
| VELOCITY_Y | 116 |
| VELOCITY | 117 |
| VELOCITY_INDICATED | 118 |
| MAGVAR | 119 |
| COURSE | 120 |
| AUTOPILOT_MASTER | 121 |
| AUTOPILOT_HEADING_ | |
| HOLD | 122 |
| AUTOPILOT_HEADING | 123 |
| AUTOPILOT_ALTITUDE_ | |
| HOLD | 124 |
| AUTOPILOT_ALTITUDE | 125 |
| AUTOPILOT_WING_ | |
| LEVELER | 126 |
| AUTOPILOT_ATTITUDE_ | |
| HOLD | 127 |
| AUTOPILOT_APPROACH_ | |
| HOLD | 128 |
| AUTOPILOT_NAV_HOLD | 129 |
| AUTOPILOT_LOCALIZER_ | |
| HOLD | 130 |
| AUTOPILOT_BACK_ | |
| COURSE_HOLD | 131 |
| EMERGENCY_FAILURE | 132 |
| RETRACTABLE_GEAR | 133 |
| ENGINE_TYPE | 134 |
| SMOKE_SYSTEM_ON | 135 |
| CLOUD_LOW_ICING | 136 |
| CLOUD_HIGH_ICING | 137 |
| CLOUD_THUNDER_ICING | 138 |
| ON_GROUND | 139 |
| AIRSPEED_INDICATOR_FAIL | 140 |
| AIRSPEED_INDICATOR_TAS | 141 |
| ALTIMETER_FAIL | 142 |
| ANGLE_OF_ATTACK | 143 |
| ATTITUDE_INDICATOR_FAIL | 144 |
| AUTO_COORDINATION | 145 |
| FLAPS_CONTROL | 146 |
| G_LOAD | 147 |
| GEAR_FAIL | 148 |
| GEAR_CONTROL | 151 |
| HEADING_INDICATOR_FAIL | 152 |
| PANEL_LIGHTS | 153 |
| PANEL_LIGHTS_FAIL | 154 |
| STROBES | 155 |
| STROBES_FAIL | 156 |
| TURN_COORDINATOR_FAIL | 157 |
| TURN_COORDINATOR_BALL | 158 |
| VERTICAL_SPEED_FAIL | 159 |
| VOR_1_COURSE_ | |
| DEVIATION | 160 |
| VOR_1_GS_DEVIATION | 161 |
| VOR_2_COURSE_ | |
| DEVIATION | 162 |
| APL_SOUND | 163 |
| APL_MESSAGES | 164 |
| INSTRUCTOR_CONTROL | 165 |
| THROTTLE_1 | 166 |
| THROTTLE_2 | 167 |
| THROTTLE_3 | 168 |
| THROTTLE_4 | 169 |
| ELAPSED_TIME | 170 |
| VOR_1_TO_FROM | 171 |
| VOR_2_TO_FROM | 172 |
| ADF_BEARING | 173 |
| ENGINE_CONTROL_SELECT | 174 |
| EVENT_COUNT | 175 |