Compilation in Unix-like systems that have GCC and SDL installed: make This documentation represents IBNIZ version 1.2 released on 2012-01-XX. The distribution licence is the "zlib/libpng licence" (see licence.txt). === OVERVIEW === IBNIZ is a virtual machine designed for extremely compact low-level audiovisual programs. The leading design goal is usefulness as a platform for demoscene productions, glitch art and similar projects. Mainsteam software engineering aspects are considered totally irrelevant. IBNIZ stands for Ideally Bare Numeric Impression giZmo. The name also refers to Gottfried Leibniz, the 17th-century polymath who, among all, invented binary arithmetic, built the first four-operation calculating machine, and believed that the world was designed with the principle that a minimal set of rules should yield a maximal diversity. The IBNIZ virtual machine is basically a two-stack machine somewhat similar to Forth implementations but with the major difference that the stack is cyclical and also used as output buffer. The machine runs in an endless loop by default, with the loop counter variable(s) pushed on top of the stack on every loop cycle. Each instruction is one character long, with the exception of 'loadimm' which consists of a string of hexadecimal digits. This also gives IBNIZ some flavor of an esoteric programming language. NOTE: IBNIZ has not been fully defined or implemented yet! Anything mentioned in this document may change (although major changes are unlikely). === QUICK TUTORIAL === The primary implementation of IBNIZ is interactive. You can edit the code like in a normal text editor, start/pause it with f1 and restart it with f2. The simplest example program is the empty program; it uses the loop variables directly as pixel values and audio data. A slightly longer example program would be: ^xp Which consists of three operations: ^ (xor), x (exchange) and p (pop). In the default video context mode ("TYX-video"), the machine pushes the variables T, Y and X on top of the main stack on every loop cycle. The first opcode (xor) replaces the two topmost values on the stack (Y and X) with their exclusive OR (Y XOR X). The next opcode is (exchange) corresponds to Forth's SWAP. It swaps the topmost values on the stack. So, after this operation, T is on top of the stack and Y XOR X is under it. The last opcode, 'pop' ('p') corresponds to Forth's DROP and moves the stack pointer so that the value on top of the stack gets 'popped off'. So, after the execution of the three instructions '^xp', the values T Y X have been transformed into Y XOR X. Whatever data remains in the stack is interpreted as pixel colors in the YUV colorspace (bit format VVUU.YYYY; thus, the integer part roughly corresponds to hue and the fraction part to intensity). As the range of X and Y is between -1.0 and +1.0 (FFFF.0000 .. 0000.FFFF), the picture resulting from X XOR Y will have a full intensity range but the only hues are 0000 (pure gray) and FFFF (nearly pure gray). The unit for T, by the way, is 1/60 seconds. The video stack is two video pages long. The visible page is flipped every time the stack pointer passes a page boundary. An audio example: d3r15&* In the audio context, only one value (T) is pushed on top of stack on each loop cycle. The first opcode 'd' duplicates it, 3r rotates the duplicate right by three bits, 15& ands it with hex number 15 (decimal 21) and * multiplies the result with the original T. In the audio context, T has the same rate as in video mode; the integer part increments 60 times per seconds. However, the fraction part is also used (resulting in a theoretical maximum sample rate of nearly 4 MHz). Of the values left on stack, only the fraction part is used. It is interpreted as a 16-bit unsigned linear PCM value. Regardless of the actual sampling rate of the implementation, the audio stack is one second long. IBNIZ always tries to execute programs simultaneously in video and audio contexts. There are two different modes for the video context: the previously-mentioned TYX-video (which pushes T Y X on every loop as three separate numbers) and T-video (which combines these variables in a single value). IBNIZ automatically detects the correct mode by stack usage. It is possible to separate video and audio calculation using the 'mediaswitch' opcode ('M'). The execution of these separate program portions is scheduled by VM-level logic: in normal cases, the video context loop is run 64 times per audio context loop cycle. *x~FF&* M d3r15&* IBNIZ is a universal programming language, not just an expression evaluator. The secondary stack (return stack or "rstack") makes it possible to implement advanced program control features such as loops, subroutines and recursion. It is also possible to ignore the exterior loop altogether and write to the buffers like to any random access memory as well as to read user input and to have a separate data segment for any arbitrary data. === TECHNICAL NUMBERS** === Technical specs of the default configuration: Word width: 32 bits (arithmetic in 16.16 fixed-point) Address space: 2^20 words (4 megabytes, ~3 of which free user RAM) Video output: 256x256 pixels at 60 Hz, 32 bits per pixel (VVUU.YYYY) Audio output: 61440 Hz mono (30720 Hz stereo), 16 bits per sample Computation speed: not defined yet (fully depends on underlying hardware) === FULL INSTRUCTION SET === Everything is case-sensitive here! NUMBERS symbol name stack ------ ---- ----- 0-F. loadimm (-- val) The basic numeric type is the 32-bit fixed-point number, divided into 16 bits of integer and 16 bits of fraction. The number format in the source code is upper-case hexadecimal using the digits 0-9 and A-F. The separator '.' can be used to separate the fraction part from the integer part. Several immediate numbers can be separated with a blank or comma (','). ARITHMETIC symbol name stack ------ ---- ----- + add (a b -- a+b) - sub (a b -- a-b) * mul (a b -- a*b) / div (a b -- a/b, 0 if b==0) % mod (a b -- a MOD b, 0 if b==0) q sqrt (a -- square root of a; 0 if a<0) & and (a b -- a AND b) | or (a b -- a OR b) ^ xor (a b -- a XOR b) r right (a b -- a ROR b) l left (a b -- a << b) ~ neg (a -- NOT a) s sin (a -- sin(a*2PI)) a atan (a b -- atan2(a,b)/2PI) < isneg (a -- a if a<0, else 0) > ispos (a -- a if a>0, else 0) = iszero (a -- 1 if a==0, else 0) All numbers used in arithmetic are interpreted as signed 16+16-bit fixed-point values (negative numbers in two's complement). The modulus (%) uses fractions. STACK MANIPULATION symbol name stack description ------ ---- ----- ---------- d dup (a -- a a) p pop (a --) same as Forth's DROP x exchange (a b -- b a) same as Forth's SWAP v trirot (a b c -- b c a) same as Forth's ROT ) pick (i -- val) load value from STACK[top-1-i] ( bury (val i --) store value to STACK[top-2-i] The operations 'pick' and 'bury' and 'movesp' are always wrapped within the stack range. The symbol 'v' was chosen because it resembles a triangle. EXTERIOR LOOP symbol name description ------ ---- ----------- M mediaswitch switches between audio and video context w whereami pushes exterior loop variable(s) on stack T terminate stops program execution The execution starts in the video context. When the execution wraps from the end of the program to the beginning, the VM implicitly executes 'mediaswitch' and 'whereami'. The loop variables pushed by 'whereami' depend on the stack pointer and internal video/audio frame counters. The exact operation, depending on context and mode, is as follows: context mode pushes on stack ------- ---- --------------- video TYX TTTT.0000, YYYY.YYYY, XXXX.XXXX where - YYYY.YYYY and XXXX.XXXX are between -1 and +1 (FFFF.0000 and 0000.FFFF) - TTTT is the frame counter (time in 60ths of second) video T TTTT.YYXX where - TTTT is the frame counter - YY and XX range from 00 to FF (directly from SP) audio T TTTT.TTTT where - the integer is the frame counter (same as in video) - the fraction is, well, the 65536th part thereof The current implementation changes the video context mode automatically based on stack balance and how many times 'whereami' is called. MEMORY MANIPULATION symbol name stack ------ ---- ----- @ load (addr -- val) ! store (val addr --) All the memory is addressed in 32-bit-wide chunks. There is no byte-level operation. The fractional part of the memory address is interpreted as the high part of the logical address. (e.g. 1234.FFFF refers to the address FFFF1234). In the default configuration, the top 12 bits of the address are ignored (thus, the actual address in the previous example is F1234). The total address space is therefore 1 megaword == 4 megabytes. It is divided as follows: 00000 - BFFFF free for user data C0000 - C7FFF reserved for internal registers, code, etc. C8000 - CBFFF return stack for audio context CC000 - CFFFF return stack for video context D0000 - DFFFF audio stack E0000 - EFFFF video stack page 0 F0000 - FFFFF video stack page 1 PROGRAM CONTROL Conditional execution symbol name description ------ ---- ----------- ? if (cond --) ; if cond==0, skip until 'else' or 'endif' : else skip until after next 'endif' ; endif nop; marks end of conditional block when skipping End of code is also regarded as a skip terminator in all cases. Loops symbol name description ------ ---- ----------- X times (i0 --) loop i0 times (push i0 and insptr on rstack) L loop decrement RSTACK[top-1], jump back if non-0 i index (-- i) load value from RSTACK[top-1] j outdex (-- j) load value from RSTACK[top-3] [ do begin loop (push insptr on rstack) ] while (cond --) jump back if cond!=0 J jump (v --) set instruction pointer to value v Examples of loop constructs: 100X 3i@L stores the number '3' to addresses 1..100 [1r dA0-<] shifts number right until it is below A0 The jump instruction (like all ops that manipulate instruction pointer directly) wraps around the code length (it is not possible to jump outside the program space). As the internal encoding of programs has not been defined yet, the exact addresses of the instructions are implementation-dependent. The times-loop counters (i and j) are regarded as 32-bit unsigned integers in the same way as memory addresses (.0001 = 10000). Thus, times-loops with more than 65535 steps are possible. Subroutines symbol name stack description ------ ---- ----- ----------- { defsub (i --) define subroutine (store pointer to MEM[i]) } return end of subroutine; pop insptr from rstack V visit (i --) visit subroutine pointed to by MEM[i] The return stack is used for storing the return addresses when visiting subroutines. Defsub ('{') stores the address of the next instruction to the memory address given by the value on top of stack and then skips instructions until '}' or end-of-code is reached. Return stack manipulation symbol name stack rstack description ------ ---- ----- ------ ----------- R retaddr (-- val) (val --) moves from rstack to stack P pushtors (val --) (-- val) moves from stack to rstack The return stack is cyclical just like the main stack. INPUT symbol name stack description ------ ---- ----- ------------ U userin (-- inword) get data from input device The 'userin' instruction polls data from the input device. It returns a word in the format MMKK.YYXX where: - YYXX indicates the last known position, in unsigned coordinates, of the pointing device (mouse, touch, lightpen, etc.) - KK indicates the unicode number of the last character entered on keyboard, or 0 if no character is entered. If the unicode number is above FF, it is wrapped to between 00 and FF. The value is cleared to zero (or the next character in the buffer) whenever 'U' is used. - MM is a bit structure indicating the state of click/state and a couple of keyboard keys. Bits from top to bottom: 80: click state (1 when a screen position is being clicked/touched) 40: ctrl key (1 = down) 20: alt/meta key 10: shift key 08: cursor up key 04: cursor down key 02: cursor left key 01: cursor right key DATA SEGMENT symbol name description ------ ---- ----------- G getdata (numbits -- data) $ startdata end code segment, start data segment A "data segment" containing arbitrary binary data can be defined after the program code. Startdata ($) ends the code segment and starts the data segment. When a program is started, the memory is filled with the contents of the data segment without any alignment. Getdata ('G') can be used for reading the data segment sequentially. It fetches the given number of next bits from the data segment. When it runs out of data, it wraps back to the beginning. In the source code, the data is encoded as digits that represent 1-4 bits in the memory. The following symbols are available: symbol name description ------ ---- ----------- 0-F data encodes a digitful (1-4 bits) of data. b binary sets digit length to 1 bit q quarternary sets digit length to 2 bits o octal sets digit length to 3 bits h hexadecimal sets digit length to 4 bits (default) META symbol name desc ------ ---- ---- \ comment ignore characters in source code until newline , blank nop; also whitespaces and newlines count as blank === PRIMARY IMPLEMENTATION === EDITOR COMMANDS Tab toggles the editor display on/off. When the editor is hidden, keyboard commands don't affect the editor state. Cursor keys etc. work as expected. Shift+cursor selects an area. Ctrl+up/down increments/decrements the number under cursor, with carry. Ctrl+left/right jumps to the final character of the previous or next "word" (i.e. blank-separated section). f1 runs and pauses the code. f2 resets the VM state (including timer and memory). Changes to the source code automatically recompile it but do not restart it. This makes it convenient to do runtime changes to numeric parameters etc. This functionality may change in the future. ESC exits the program. Ctrl+C/X/V/A work as copy/cut/paste/selectall. Ctrl+S saves the program to the file indicated by a line beginning with '\#file' (or if there's no such line, inserts the line '\#file untitled.ib' and uses untitled.ib as the filename. The '\#file' lines are automatically skipped when saving. COMMAND LINE OPTIONS -h Dump help on command line usage -v Dump version info -c CODE Execute code -n No autorun of loaded code The following extra options were added for creating the YouTube video: -e Dump user keystrokes to stdout -p Playback dumped user keystrokes from stdin -M Dump raw video to stdout and raw audio to stderr. 30 fps, non-realtime, yuv4mpeg2 and pcm_s16. Some commands used in this process, for reference: ./ibniz -e > events ./ibniz -M -p < events 2>vid.pcm | ffmpeg -y -i - -r 30 vid.avi ffmpeg -i vid.avi -f s16le -ar 44100 -ac 1 \ -i vid.pcm -vcodec copy vidav.avi === EXAMPLES === \ 2-character programs: *d \ TV noise (without sound) ** \ Mul-texture zoomer 9/ \ Flasher +/ \ "Jupiter storm" +% \ "Jupiter storm" in B&W /% \ Perspective mapper &* \ Sierpinski epilepsy qs \ Polyrhythmic flasher slowing down )~ \ Sliding-down squarewave \ "42 melody" d3r15&* \ Plasma sv5rvs-- \ Munching squares with a Sierpinski harmony ^x7r+Md8r& \ Xor texture zoomer v8rsdv*vv*^ \ Music from the video d6r|5*wdAr&+ \ "Opening gate" (from FreeFull) 8rw10r%w18r% \ "Spinny" (from FreeFull) sxsaxAr+waxBr+^ \ Munching squares zoomer v8rsdv*vv*^wpp8r- \ Texture tunnel ax8r+3lwd*xd*+q1x/x5r+^ \ Rotozoomer v8rds4X3)Lx~2Xv*vv*+i!L1@2@& \ Mandelbrot zoomer (76 chars) vArs1ldv*vv*0!1-1!0dFX4X1)Lv*vv*-vv2**0@+x1@+4X1)Lv*vv*+4x->?Lpp0:ppRpRE.5*; \ Julia morpher (from real_het) (97 chars) 2*2!2*3!10rdF2*s0!F9*s1!10,6! [2@d3@*4!d*2!3@d*3!3@2@+2@3@-0@+2!4@d+1@+3!4-<6@1-d6!*]6@4r.FF^1977+ \ The 122-char demo from the video 6{^^ddd***1%} 5{v8rsdv*vv*^wpp8r-} 4{v8rdsx.6+s4X3)Lx~2Xv*vv*+i!L1@2@^} 3{ax8r+3lwd*xd*+q1x/x6r+^} 2)6r3&3+V55A9^Md6r|5*wdAr&+ \ Bitmap zoomer from the video v7rs6ldv*vv*7&@xr.8&$b 00000000000000000000000000000000 00000000011110111010010011101110 00000000010000010010110100100100 00000000001000010011010011100100 00000000000100010010010100100100 00000000000010010010010100100100 00000000011110111010010011101110 00000000000000000000000000000000 === CHANGES === 1.1000 - Cut/copy/paste implemented, with system clipboard support on X11 and W32. - VM no longer eats up all CPU time if less is enough for 60 fps. - Possibility to hide on-screen display (with autohide on autorun) - Scrolling and buffer size limit check in the editor - More examples included in the distribution package - Help screen implemented 1.1800 - Clipboard bugs fixed, window icon added - Machine status panel implemented === FUTURE === Tasks in an approximate order of priority: - Fix problems that prevent IBNIZ from working in some systems - Fix other known bugs - On-screen machine status info - Improve execution speed with static code analysis and native compilation - Support resolution reduction etc for slow code/machines - Remove MSVC library dependency from Win32 build - Make it possible to limit execution speed - Make internal registers user-accessible - Implement IBNIZ as a website - Native Win32 version (without MSVC library or the statically linked SDL) - Define and implement a compact bitwise machine code - Allow self-modifying code - Support threading, shaders etc. - Native version for MS-DOS, ibniz-to-c64 compiler etc. Once we have all of these, we may call the version number 2.0.