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author=Mark Moxon;
description=Fully documented source code disassembly for Acornsoft Aviator on the BBC Micro, with lots of deep dive articles explaining how every aspect of the game works.;

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the, aviator, on, bbc, micro, code, for, fully, documented, source, suggestions, your, visit, if, you, want, to, play, with, similar, projects, 100, handcrafted,

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the (575), and (140), for (136), part (134), line (70), #aviator (52), code (51), indicator (47), point (46), #source (44), byte (42), high (38), alien (37), that (34), object (34), coordinates (31), main (30), screen (30), variables (28), this (28), draw (28), coordinate (28), calculate (27), game (26), process (26), are (25), update (24), from (23), start (22), set (21), bit (21), key (21), lines (20), canopy (20), low (20), check (19), points (18), whether (18), objects (18), with (17), number (17), aliens (17), calculations (17), flight (17), value (17), colour (17), plane (17), bbc (16), micro (16), subroutines (16), each (16), bytes (16), pixel (16), list (15), all (15), which (15), loop (15), storage (15), mainloop (15), updateindicator (15), how (15), runway (14), score (14), you (14), out (13), visibility (13), can (13), routines (13), sound (13), lookup (13), table (13), buffer (13), site (13), more (12), into (12), vector (12), make (12), flying (12), drawing (12), any (11), 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envelopes, envelopedata, toggleenginesound, resetenginesound, pressed, processvolumekeys, either, makesoundenvelope, makesound, choppiness, affected, makeenginesound, define, defineenvelope, please, wait, loads, pleasewaittext, string, loading, loaddashboard, disabling, disablecursor, terminategame, startgame, mode, load, setupscreen, prepare, resetvariables, newgame, rivets, drawcanopy, setup, sizes, zones, skillzonesize, skillzonelo, skillzonehi, scoretext, scorelo, scorehi, highscorelo, highscorehi, updatescore, updatehighscore, beep, scorepoints, required, scorehitpoints, removescore, showing, printscoretext, printscore, displayscore, finer, performing, tests, safely, checkbridgeandtown, awarding, buzzing, scoring, timestable, sinlo, sinhi, shift4right, shift4left, matrix4lo, matrix4hi, matrix3lo, matrix3hi, matrix2lo, matrix2hi, matrix1lo, matrix1hi, lownibble, highnibble, divisionlo, divisionhi, sine16bit, until, retaining, sensitivity, smaller, scalesigned, balance, results, divisions, done, negate, negate16bit, multiply8x8, multiply8x16, multiply4x16, multiply16x16mix, multiply16x16bit0, multiply16x16, divide, subtract, addscaled, add16x16bit0, subtraction, only, timely, fashion, previoustime, mainloopcounter, handle, spend, least, successful, switched, enable, increment, invaded, firing, appropriate, statuses, runs, keytable2lo, keytable2hi, keytable1lo, keytable1hi, updatekeylogger, toggle, togglejoystick, specific, scankeyboard, button, readjoystick, adc, channels, readadcchannel, processotherkeys, joysticks, ylookuplo, ylookuphi, xlookuplo, xlookuphi, vdupoint, vduplot, vdumove, vdudraw, physical, setlogicalcolour, white, setcolourtowhite, setcolourtoblack, flip, colourcycle, colourlogic, flipcolours, particular, avoiding, fillcanopyrows, fillcanopy, square, rivet, across, drawrivet, gun, sights, drawgunsights, drawcanopyview, diagonal, drawcanopycorners, clearrows, clearcanopy, general, clearing, signed, powers, scalefactor, fuelusedlo, fuelusedhi, fuellevel, multiplied, scaling, forcefactor, moved, axischangerate, brake, throttle, control, setengine, relevant, scaleflightforces, altitude, scalebyaltitude, retract, 150, mph, retractflapsiffast, successfully, touched, without, tilt, backwards, touching, emergency, bumpy, rolling, yawing, moments, due, yaw, rates, getmoments, 65th, full, fillupfueltank, flash, crash, checkplaneonrunway, ylinear, zlinear, dyturn, dzturn, rotate, according, vectors, sliprate, near, perspective, effect, gravity, springs, primary, ailerons, implement, instant, feature, applyflightcontrol, bumpiness, applybumpyride, figures, simulate, wing, adjustvelocity, adjustturn, adjustrotation, realistic, linebufferw, linebufferv, linebuffert, linebuffers, linebufferr, linebufferg, colour2row, colour2r2l, colour2l2r, colour1row, colour1r2l, colour1l2r, swaplinepoints, modifydrawroutine, erasecanopylines, step, orthogonal, drawortholine, drawjoystickcross, drawindicatorline, limits, drawindicatorhand, drawindicatorbar, half, drawhalfhorizon, was, edge, steepness, completely, best, clipbestendofline, yradarbuffer, yjoycoord, ydeltamax, xradarbuffer, xjoycoord, xdeltamax, heading, later, previouscompass, joycoord, minimum, indicatormin, indicatormax, indicatorlinev, indicatorlineu, indicatorlinet, indicatorlinej, indicatorlinei, base, indicatorbase, indicator7to11, indicator0to6, quadrant, dialquadrant, large, altitudeminutes, updateradarblip, bottom, speed, small, hour, updatefuelgauge, subsequent, updatedashboard, upside, showupsidedownbar, resetradar, indicatoru, indicatort, indicatorf, indicatorb, dot, getradarvector, gethandvector, drawradarblip, drawfuelpixel, artificialhorizon, radars, zpointhi, zobjectpoint, zobjectlo, zobjecthi, zgroupobjecthi, yobjectpoint, yobjectlo, yobjecthi, 255, xtemppoint2hi, 254, xtemppoint1hi, xpointhi, xobjectpoint, xobjectlo, xobjecthi, 252, xlinearhi, xgroupobjecthi, 253, xgravityhi, sequences, together, objectpoints, objectgroup, total, numberoflines, linestartpointid, lineendpointid, groupstart, indicate, calculated, setpointvisibility, origin, setpointtoorigin, setpointcoords, setpoint, factor, setobjecttoorigin, applicable, groups, location, setmatrixentry, setmatrices, angles, projectaxisangle, nextobjectgroup, overflowed, store, another, overflows, addpointtoobject, transformations, configuration, overview, structured, file, snippets, tell, clues, binary, sure, press, gets, recorded, loggers, generates, cosine, inside, algorithms, arithmetic, thing, scheduling, tasks, sequence, events, program, flow, task, scheduler, caching, buffers, colours, super, animated, flicker, serious, consequences, spots, detecting, hits, spawning, leave, tracer, trails, sky, planning, civilisation, life, growth, patterns, everything, tailored, fast, hard, coded, hands, bridges, behaviour, dangerous, parts, offs, landings, modelling, rip, clean, ripping, simulates, tracking, features, mentioned, manual, matching, simulation, simulating, 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Text of the page (random words):
horizon on indicator 7 drawfuelpixel draw or erase a pixel on the fuel gauge on the dashboard drawradarblip draw a blip on the radar runway or alien gethandvector vector line calculation for a hand on indicators 0 to 6 getradarvector calculate the radar line vector for a line the runway or a dot an alien indicatorb update the brakes indicator b indicatorf update the flaps indicator f and related variables indicatort update the theme indicator t indicatoru update the undercarriage indicator u and related variables resetradar reset the radar display showupsidedownbar show or hide the upside down bar in the artificial horizon indicator updatedashboard update two indicators on the dashboard one from 0 6 one from 7 11 cycling through them with each subsequent call updatefuelgauge update the fuel gauge every 16 iterations of the main loop updateindicator part 1 of 15 update a single indicator on the dashboard updateindicator part 2 of 15 calculations for the compass indicator 0 updateindicator part 3 of 15 calculations for the airspeed indicator indicator 1 updateindicator part 4 of 15 calculations for the altimeter s small hour hand indicator 2 updateindicator part 5 of 15 calculations for the altimeter s minute hand indicator 3 updateindicator part 6 of 15 logic for checking which indicator to update updateindicator part 7 of 15 calculations for the vertical speed indicator indicator 4 updateindicator part 8 of 15 logic for checking which indicator to update updateindicator part 9 of 15 calculations for the turn indicator indicator 5 the bottom part of the slip and turn indicator updateindicator part 10 of 15 calculations for the slip indicator indicator 6 the top part of the slip and turn indicator updateindicator part 11 of 15 calculations for the artificial horizon indicator 7 updateindicator part 12 of 15 logic for checking which indicator to update updateindicator part 13 of 15 calculations for the rudder indicator indicator 9 updateindicator part 14 of 15 calculations for the joystick position display indicator 8 or 10 updateindicator part 15 of 15 calculations for the thrust indicator indicator 11 updateradarblip update a blip on the radar runway or alien variables altitudeminutes the value of the altimeter s large minute hand dialquadrant the value range of a quadrant in each indicator indicator0to6 the first indicator counter indicator7to11 the second indicator counter indicatorbase the base value for each indicator indicatorlinei line buffer storage for the start x coordinate for each indicator line i indicatorlinej line buffer storage for the start y coordinate for each indicator line j indicatorlinet line buffer storage for the indicator line s x delta t indicatorlineu line buffer storage for the indicator line s y delta u indicatorlinev line buffer storage for the indicator line s direction v indicatormax the maximum value shown on each indicator indicatormin the minimum value shown on each indicator joycoord temporary storage previouscompass stores the value of the compass heading when we draw the runway on the radar so we can erase the line later xdeltamax the maximum x delta for the hand line in each indicator xjoycoord temporary storage xradarbuffer the x coordinates of the runway and alien on the radar ydeltamax the maximum y delta for the hand line in each indicator yjoycoord temporary storage yradarbuffer the y coordinates of the runway and alien on the radar drawing lines the core line drawing routines subroutines clipbestendofline clip a line at the start or end point depending on which is best clipstartofline part 1 of 5 check whether the line is completely off screen clipstartofline part 2 of 5 work out the deltas depending on the direction of slope clipstartofline part 3 of 5 work out the deltas depending on the steepness of slope clipstartofline part 4 of 5 calculate where to clip the line clipstartofline part 5 of 5 move the start point to the clipped position and return it drawcanopyline part 1 of 9 draw a line in the canopy view drawcanopyline part 2 of 9 modify the line drawing routine for a shallow horizontal slope drawcanopyline part 3 of 9 draw a line as a shallow horizontal slope drawcanopyline part 4 of 9 draw a part of the line working down the screen drawcanopyline part 5 of 9 draw a part of the line working up the screen drawcanopyline part 6 of 9 draw a part of the line working along the screen drawcanopyline part 7 of 9 modify the line drawing routine for a steep vertical slope drawcanopyline part 8 of 9 draw a line as a steep vertical slope drawcanopyline part 9 of 9 if the line was clipped draw a line from the clipped coordinates to the edge of the screen drawclippedline part 1 of 6 clip a line to fit on screen starting with the line deltas drawclippedline part 2 of 6 work out whether the line s start point is on screen drawclippedline part 3 of 6 work out whether the line s end point is on screen drawclippedline part 4 of 6 calculate the starting point and direction for our clipped vector line drawclippedline part 5 of 6 calculate the deltas for our clipped vector line drawclippedline part 6 of 6 add the clipped line to the line buffer and draw it drawhalfhorizon draw half of the horizon line drawindicatorbar draw a vertical bar on indicator 9 rudder or 11 thrust drawindicatorhand apply min and max limits to an indicator value and draw a hand on the indicator drawindicatorline draw a line on indicators 0 to 7 i e a dial hand 0 6 or an artificial horizon 7 drawjoystickcross draw a cross in the joystick position display indicator 8 or 10 drawortholine draw an orthogonal line i e vertical or horizontal drawvectorline part 1 of 3 draw a line set up pixel bytes and slope variables drawvectorline part 2 of 3 calculate the coordinates of the next pixel as we step along the line by one pixel drawvectorline part 3 of 3 plot a pixel at i j erasecanopylines draw all the lines from a line buffer to erase them modifydrawroutine modify the drawing routines to draw in the correct colour for the current colour cycle swaplinepoints copy an end point into a start point variables colour1l2r pixel bytes for drawing canopy lines left to right in colour 1 colour1r2l pixel bytes for drawing canopy lines right to left in colour 1 colour1row pixel bytes for erasing canopy lines in colour 1 colour2l2r pixel bytes for drawing canopy lines left to right in colour 2 colour2r2l pixel bytes for drawing canopy lines right to left in colour 2 colour2row pixel bytes for erasing canopy lines in colour 2 linebufferg line buffer storage for the max min y coordinate g linebufferr line buffer storage for the start x coordinate r linebuffers line buffer storage for the start y coordinate s linebuffert line buffer storage for the line s x delta t linebufferv line buffer storage for the line direction v linebufferw line buffer storage for the max min x coordinate w flight model the aerodynamics behind the spitfire s realistic movement through the air subroutines adjustrotation move the plane and adjust its rotation adjustturn adjust the plane s turn rate adjustvelocity adjust the plane s velocity vector applyaerodynamics part 1 of 3 set up various variables to use in the aerodynamics calculations applyaerodynamics part 2 of 3 check whether the plane is stalling and if it is simulate one wing stalling before the other and make the stalling sound applyaerodynamics part 3 of 3 calculate various aerodynamic figures applybumpyride apply a random amount of roll or bumpiness to the plane applyflightcontrol calculate the effects of the primary flight controls elevator rudder and ailerons and implement the instant centre feature applyflightmodel part 1 of 7 apply the flight model to the plane starting by calculating the effect of gravity and the undercarriage springs applyflightmodel part 2 of 7 convert velocity to the plane s perspective and calculate various aerodynamic forces applyflightmodel part 3 of 7 if we are near to an exploding alien apply turbulence applyflightmodel part 4 of 7 calculate the dxturn and xlinear vectors and the sliprate applyflightmodel part 5 of 7 calculate the forces for when we are on the ground applyflightmodel part 6 of 7 adjust the plane s velocity and turn rate rotate the plane according to the forces on the aircraft process landing applyflightmodel part 7 of 7 calculate fuel usage applyturnandthrust part 1 of 2 calculate the dxturn dyturn dzturn vector applyturnandthrust part 2 of 2 calculate the xlinear ylinear zlinear vector checkplaneonrunway check whether the plane is over the runway crash make a crashing sound flash the canopy and start a new game fillupfueltank fill up the fuel tank by 1 65th of a full tank every four iterations of the main loop getmoments calculate the pitching rolling and yawing moments due to the current pitch roll and yaw rates processlanding part 1 of 7 if this is an emergency landing make the landing a bumpy one processlanding part 2 of 7 if we are too high to be touching the ground then we can t be landing so stop the landing checks processlanding part 3 of 7 if we are taxiing restrict the plane s vertical movement and roll processlanding part 4 of 7 if we are taxiing with the undercarriage up restrict pitching processlanding part 5 of 7 if we are taxiing with the undercarriage down restrict pitching and tilt the plane backwards processlanding part 6 of 7 if we are not taxiing process the landing processlanding part 7 of 7 we have successfully touched down without crashing so process the effects of landing on the plane retractflapsiffast retract the flaps if we are going faster than 150 mph scalebyaltitude multiply the high byte of the plane s altitude by a 16 bit number scaleflightforces scale the flight forces by the relevant scale factors setengine set the engine status updateflightmodel part 1 of 4 apply any axis control key presses to the current axis values updateflightmodel part 2 of 4 apply any throttle key presses to the current thrust value updateflightmodel part 3 of 4 process the undercarriage brake flaps and fire keys updateflightmodel part 4 of 4 set up matrices apply the flight model and update the dashboard variables axischangerate stores the amount by which the three axes of movement change when the aileron elevator or rudder are moved forcefactor the factors by which the flight forces are multiplied as part of the scaling process fuellevel the current fuel level fuelusedhi the high byte of the current batch of fuel used fuelusedlo the low byte of the current batch of fuel used scalefactor scale factors for the flight forces in signed powers of 2 graphics general graphics routines for drawing the canopy clearing the screen and so on subroutines clearcanopy clear the canopy to black leaving the canopy edges alone clearrows clear the specified number of rows on screen drawcanopycorners draw the diagonal corners at the top of the canopy drawcanopyview draw the main view out of the canopy drawgunsights draw the canopy corners and the gun sights if shown drawrivet draw a square rivet 2 pixels across 4 pixels high fillcanopy fill the canopy with a specified colour leaving the canopy edges alone fillcanopyrows fill multiple screen rows with a particular colour avoiding the canopy edges flipcolours flip the values of colourcycle and colourlogic to cycle to the next colour state setcolourtoblack set a logical colour to black setcolourtowhite set a logical colour to white setlogicalcolour set a logical colour to a physical colour vdudraw draw a line using the standard vdu routines vdumove move the graphics cursor using the standard vdu routines vduplot perform a plot command using the standard vdu routines vdupoint draw a point on screen using the standard vdu routines variables xlookuphi lookup table for converting pixel x coordinate to high byte of screen address xlookuplo lookup table for converting pixel x coordinate to low byte of screen address ylookuphi lookup table for converting pixel y coordinate to high byte of screen address ylookuplo lookup table for converting pixel y coordinate to low byte of screen address keyboard processing key presses and joysticks subroutines processotherkeys apply the undercarriage brakes flaps and fire keys readadcchannel read the joystick position from one of the adc channels readjoystick read the joystick axes and fire button and update the aileron elevator and fire key values accordingly scankeyboard scan the keyboard for a specific key togglejoystick toggle the joystick setting updatekeylogger scan the keyboard for keys in the two key tables and update the key logger variables keytable1 internal key numbers of high priority keys that are scanned first keytable1hi key logger value high byte for key presses in keytable1 keytable1lo key logger value low byte for key presses in keytable1 keytable2 internal key numbers of lower priority keys that are scanned second keytable2hi key logger value high byte for key presses in keytable2 keytable2lo key logger value low byte for key presses in keytable2 main loop the core game loop that runs aviator subroutines mainloop part 1 of 15 start the main loop by processing gunfire and bullets mainloop part 2 of 15 reset object statuses and related points mainloop part 3 of 15 make the sound of firing if appropriate mainloop part 4 of 15 check whether aliens have invaded acornsville mainloop part 5 of 15 update lines check flying skills increment main loop counter update the radar mainloop part 6 of 15 check whether any aliens have been hit mainloop part 7 of 15 process the terminate key mainloop part 8 of 15 if we fire the guns on the runway enable the theme mainloop part 9 of 15 fill up the tank if the engine is switched off and process the volume keys mainloop part 10 of 15 award points for a successful landing mainloop part 11 of 15 process engine start and stop mainloop part 12 of 15 spend at least 9 centiseconds processing lines from the linestohide list mainloop part 13 of 15 process more lines and update the view out of the canopy mainloop part 14 of 15 handle the score display mainloop part 15 of 15 update the status of any new line points variables mainloopcounter the main loop counter previoustime stores the current time low byte only so we can process lines in a timely fashion during the main loop maths addition subtraction multiplication division subroutines add16x16bit0 add two 16 bit numbers that have their signs in bit 0 addscaled add or subtract a scaled amount to a variable dividescaled divide a 16 bit number by a scaled 16 bit number multiply16x16 multiply two unsigned 16 bit numbers multiply16x16bit0 multiply two 16 bit numbers that have their signs in bit 0 multiply16x16mix multiply two 16 bit numbers with different sign bits one in bit 7 of the high byte the other in bit 0 of the low byte multiply4x16 multiply a 4 bit and a 16 bit number multiply8x16 multiply an 8 bit and a 16 bit number multiply8x8 multiply two unsigned 8 bit numbers negate16bit negate a 16...