-- 0x00: LINZBS LINBUG RAM 0x02: CASINI Cassette initialization vector 0x04: RAMLO RAM pointer for the memory test used on powerup 0x06: TRAMSZ Temporary Register for RAM size 0x07: TSTDAT RAM test data register 0x08: WARMST Warmstart flag 0x09: BOOT? Boot flag success indicator 0x0a: DOSVEC Start vector for disk (or non-cartridge) software 0x0c: DOSINI Initialization address for the disk boot 0x0e: APPMHI Applications memory high limit and pointer to the end of your BASIC program 0x10: POKMSK POKEY interrupts 0x11: BRKKEY Zero means the BREAK key is pressed 0x12: RTCLOK Internal realtime clock 0x15: BUFADR Indirect buffer address register (page zero) 0x17: ICCOMT Command for CIO vector 0x18: DSKFMS Disk file manager pointer 0x1a: DSKUTL The disk utilities pointer 0x1c: PTIMOT Printer timeout 0x1d: PBPNT Print buffer pointer 0x1e: PBUFSZ Print buffer size of printer record for current mode 0x1f: PTEMP Temporary register used by the printer handler for the value of the character being output to the printer 0x20: ICHIDZ Handler index number 0x21: ICDNOZ Device number or drive number Called MAXDEV by DOS to in dicate the maximum number of devices 0x22: ICCOMZ Command code byte set by the user to define how the rest of the IOCB is formatted 0x23: ICSTAZ Status of the last IOCB action returned by the device 0x24: ICBALZ/HZ Buffer address for data transfer or the address of the file name for commands such as OPEN 0x26: ICPTLZ/HZ Put byte routine address set by the OS 0x28: ICBLLZ/HZ Buffer length byte count used for PUT and GET operations 0x2a: ICAX1Z Auxiliary information first byte used in OPEN to specify the type of file access needed 0x2b: ICAX2Z CIO working variables 0x2c: ICAX3Z/4Z Used by BASIC NOTE and POINT commands for the transfer of disk sector numbers 0x2e: ICAX5Z The byte being accessed within the sector noted in locations 44 and 45 0x2f: ICAX6Z Spare byte 0x30: STATUS Internal status storage 0x31: CHKSUM Data frame checksum used by SIO 0x32: BUFRLO/HI Pointer to the data buffer 0x34: BFENLO/HI Next byte past the end of the SIO and DCB data buffer described above 0x36: CRETRY Number of command frame retries 0x37: DRETRY Number of device retries 0x38: BUFRFL Data buffer full flag (255 0x39: RECVDN Receive done flag (255 0x3a: XMTDON Transmission done flag (255 0x3b: CHKSNT Checksum sent flag (255 0x3c: NOCKSM Flag for "no checksum follows data 0x3d: BPTR Cassette buffer pointer 0x3e: FTYPE Inter-record gap type between cassette records 0x3f: FEOF Cassette end of file flag 0x40: FREQ Beep count retain register 0x41: SOUNDR Noisy I/O flag used by SIO to signal the beeping heard during disk and cassette I/O 0x42: CRITIC Critical I/O region flag 0x43: FMZSPG Disk file manager system (FMS) page zero registers (seven bytes) 0x43: ZBUFP Page zero buffer pointer to the user filename for disk I/O 0x45: ZDRVA Page zero drive pointer 0x47: ZSBA Zero page sector buffer pointer 0x49: ERRNO Disk I/O error number 0x4a: CKEY Cassette boot request flag on coldstart 0x4b: CASSBT Cassette boot flag 0x4c: DSTAT Display status and keyboard register used by the display handler 0x4d: ATRACT Attract mode timer and flag 0x4e: DRKMSK Dark attract mask 0x4f: COLRSH Color shift mask 0x50: TEMP Temporary register used by the display handler in moving data to and from screen 0x51: HOLD1 Same as location 80 0x52: LMARGN Column of the left margin of text (GR 0x53: RMARGN Right margin of the text screen initialized to 39 ($27) 0x54: ROWCRS Current graphics or text screen cursor row 0x55: COLCRS Current graphics or text mode cursor column 0x57: DINDEX Display mode/current screen mode 0x58: SAVMSC The lowest address of the screen memory 0x5a: OLDROW Previous graphics cursor row 0x5b: OLDCOL Previous graphics cursor column 0x5d: OLDCHR Retains the value of the character under the cursor used to restore that character when the cursor moves 0xe0: FR1 Floating point register one 0xe6: FR2 FP register two 0xec: FRX FP spare register 0xed: EEXP The value of E (the exponent) 0xee: NSIGN The sign of the FP number 0xef: ESIGN The sign of the exponent 0xf0: FCHRFLG The first character flag 0xf2: CIX Character (current input) index 0xf3: INBUFF Input ASCII text buffer pointer 0xf5: ZTEMP1 Temporary register 0xf7: ZTEMP4 Temporary register 0xf9: ZTEMP3 Temporary register 0xfb: RADFLG Also called DEGFLG 0xfc: FLPTR Points to the user's FP number 0xfe: FPTR2 Pointer to the user's second FP number to be used in an operation 0x200: VDSLST The vector for NMI Display List Interrupts (DLI) 0x202: VPRCED Serial (peripheral) proceed line vector 0x204: VINTER Serial (peripheral) interrupt vector 0x206: VBREAK Software break instruction vector for the 6502 BRK ($00) command 0x208: VKEYBD POKEY keyboard interrupt vector 0x20a: VSERIN POKEY serial I/O bus receive data ready interrupt vector 0x20c: VSEROR POKEY serial I/O transmit ready interrupt vector 0x20e: VSEROC POKEY serial bus transmit complete interrupt vector 0x210: VTIMR1 POKEY timer one interrupt vector 0x212: VTIMR2 POKEY timer two vector for AUDF2 (53762 0x214: VTIMR4 POKEY timer four vector for AUDF4 (53766 0x216: VIMIRQ The IRQ immediate vector (general) 0x218: CDTMV1 System timer one value 0x21a: CDTMV2 System timer two 0x21c: CDTMV3 System timer three 0x21e: CDTMV4 System timer four 0x220: CDTMV5 System timer five 0x222: VVBLKI VBLANK immediate register 0x224: VVBLKD VBLANK deferred register 0x226: CDTMA1 System timer one jump address 0x228: CDTMA2 System timer two jump address 0x22a: CDTMF3 System timer three flag 0x22b: SRTIMR Software repeat timer 0x22c: CDTMF4 System timer four flag 0x22d: INTEMP Temporary register used by the SETVBL routine at 58460 ($E45C) 0x22e: CDTMF5 System timer five flag 0x22f: SDMCTL Direct Memory Access (DMA) enable 0x230: SDLSTL Starting address of the display list 0x232: SSKCTL Serial port control register 0x233: SPARE No OS use 0x234: LPENH Light pen horizontal value shadow for 54284 ($D40C) 0x235: LPENV Light pen vertical value 0x236: BRKKY BREAK key interrupt vector 0x23a: CDEVIC Four-byte command frame buffer (CFB) address for a device - used by SIO while performing serial I/O 0x23b: CCOMND The SIO bus command code 0x23c: CAUX1 Command auxiliary byte one 0x23d: CAUX2 Command auxiliary byte two 0x23e: TEMP Temporary RAM register for SIO 0x23f: ERRFLG SIO error flag 0x240: DFLAGS Disk flags read from the first byte of the boot file (sector one) of the disk 0x241: DBSECT The number of disk boot sectors read from the first disk record 0x242: BOOTAD The address for where the disk boot loader will be put 0x244: COLDST Coldstart flag 0x246: DSKTIM Disk time-out register (the address of the OS worst case disk time out) 0x247: LINBUF Forty-byte character line buffer 0x26f: GPRIOR Priority selection register 0x270: PADDL0 The value of paddle 0 0x271: PADDL1 The value of paddle 1 0x272: PADDL2 The value of paddle 2 0x273: PADDL3 The value of paddle 3 0x274: PADDL4 The value of paddle 4 0x275: PADDL5 The value of paddle 5 0x276: PADDL6 The value of paddle 6 0x277: PADDL7 The value of paddle 7 0x278: STICK0 The value of joystick 0 0x279: STICK1 The value of joystick 1 0x27a: STICK2 The value of joystick 2 0x27b: STICK3 The value of joystick 3 0x27c: PTRIG0 Paddle trigger 0 0x27d: PTRIG1 Paddle trigger 1 0x27e: PTRIG2 Paddle trigger 2 0x27f: PTRIG3 Paddle trigger 3 0x280: PTRIG4 PTRIG 4-7 are shadows for PIA register 54017 ($D301) 0x281: PTRIG5 PTRIG 4-7 are shadows for PIA register 54017 ($D301) 0x282: PTRIG6 PTRIG 4-7 are shadows for PIA register 54017 ($D301) 0x283: PTRIG7 PTRIG 4-7 are shadows for PIA register 54017 ($D301) 0x284: STRIG0 Stick trigger 0 0x285: STRIG1 Stick trigger 1 0x286: STRIG2 Stick trigger 2 0x287: STRIG3 Stick trigger 3 0x288: CSTAT Cassette status register 0x289: WMODE Register to store either the read or the write mode for the cassette handler 0x28a: BLIM Cassette data record buffer size 0x290: TXTROW Text window cursor row 0x291: TXTCOL Text window cursor column 0x293: TINDEX Contains the current split-screen text window GRAPHICS mode 0x294: TXTMSC Address of the upper left corner of the text window 0x296: TXTOLD These locations contain the split-screen equivalents of OLDROW 0x29c: TMPX1 Temporary register 0x29d: HOLD3 Temporary register 0x29e: SUBTMP Temporary storage 0x29f: HOLD2 Temporary register 0x2a0: DMASK Pixel location mask 0x2a1: TMPLBT Temporary storage for the bit mask 0x2a2: ESCFLG Escape flag 0x2a3: TABMAP Map of the TAB stop positions 0x2b2: LOGMAP Logical line start bit map 0x2b6: INVFLG Inverse character flag 0x2b7: FILFLG Right fill flag for the DRAW command 0x2b8: TMPROW Temporary register for row used by ROWCRS 0x2b9: TMPCOL Temporary register for column used by COLCRS 0x2bb: SCRFLG Scroll flag 0x2bc: HOLD4 Temporary register used in the DRAW command only 0x2bd: HOLD5 Same as the above register 0x2be: SHFLOK Flag for the shift and control keys 0x2bf: BOTSCR Flag for the number of text rows available for printing 0x2c0: PCOLR0 Color of player 0 and missile 0 0x2c1: PCOLR1 Color of player and missile 1 0x2c2: PCOLR2 Color of player and missile 2 0x2c3: PCOLR3 Color of player and missile 3 0x2c4: COLOR0 Color register zero 0x2c5: COLOR1 The next four locations are the same as location 708 for the different playfields and SETCOLOB commands 0x2c6: COLOR2 The same as above for playfield two 0x2c7: COLOR3 The same as the above but for playfield three 0x2c8: COLOR4 The same as the above but for the background (BAK) and border color 0x2e0: GLBABS Global variables 0x2e0: RUNAD Used by DOS for the run address read from the disk sector one or from a binary file 0x2e2: INITAD Initialization address read from the disk 0x2e4: RAMSIZ RAM size 0x2e5: MEMTOP Pointer to the top of free memory used by both BASIC (which calls it HIMEM) and the OS 0x2e7: MEMLO Pointer to the bottom of free memory 0x2ea: DVSTAT Four device status registers used by the I/O status operation as follows 0x2ee: CBAUDL/H Cassette baud rate low and high bytes 0x2f0: CRSINH Cursor inhibit flag 0x2f1: KEYDEL Key delay flag or key debounce counter 0x2f2: CH1 Prior keyboard character code (most recently read and accepted) 0x2f3: CHACT Character Mode Register 0x2f4: CHBAS Character Base Register 0x2fa: CHAR Internal code value for the most recent character read or written (internal code for the value in ATACHR) 0x2fb: ATACHR Returns the last ATASCII character read or written or the value of a graphics point 0x2fc: CH Internal hardware value for the last key pressed 0x2fd: FILDAT Color data for the fill region in the XIO FILL command 0x2fe: DSPFLG Display flag 0x2ff: SSFLAG Start/stop display screen flag 0x300: DDEVIC Device serial bus ID (serial device type) set up by the handler 0x301: DUNIT Disk or device unit number 0x302: DCOMND The number of the disk or device operation (command) to be performed 0x303: DSTATS The status code upon return to user 0x304: DBUFLO/HI Data buffer address of the source or destination of the data to be transferred or the device status information (or the disk sector data) 0x306: DTIMLO The time-out value for the handler in one-second units 0x307: DUNUSE Unused byte 0x308: DBYTLO/HI The number of bytes transferred to or from the data buffer (or the disk) as a result of the most recent operation 0x30a: DAUX1/2 Used for device specific information such as the disk sector number for the read or write operation 0x30c: TIMER1 Initial baud rate timer value 0x30e: ADDCOR Addition correction flag for the baud rate calculations involving the timer registers 0x30f: CASFLG Cassette mode when set 0x310: TIMER2 Final timer value 0x312: TEMP1 Two-byte temporary storage register used by SIO for the VCOUNT calculation during baud timer routines 0x314: TEMP2 Temporary storage register 0x315: TEMP3 Ditto 0x316: SAVIO Save serial data-in port used to detect 0x317: TIMFLG Time-out flag for baud rate correction 0x318: STACKP SIO stack pointer register 0x319: TSTAT Temporary status holder for location 48 ($30) 0x31a: HATABS Handler Address Table 0x340: IOCB0 I/O Control Block (IOCB) zero 0x350: IOCB1 IOCB one 0x360: IOCB2 IOCB two 0x370: IOCB3 IOCB three 0x380: IOCB4 IOCB four 0x390: IOCB5 IOCB five 0x3a0: IOCB6 IOCB six 0x3b0: IOCB7 IOCB seven 0x3c0: PRNBUF Printer buffer 0x3fd: CASBUF Cassette buffer 0x57e: LBPR1 LBUFF prefix one 0x57f: LBPR2 LBUFF prefix two 0x580: LBUFF BASIC line buffer 0x5e0: PLYARG Polynomial arguments (FP use) 0x5e6: FPSCR FP scratch pad use 0x5ec: FPSCR1 Ditto 0x1d7c: (maximum) Non-resident portion of DUP 0x709: SABYTE This records the limit on the number of files that can be open simultaneously 0x70a: DRVBYT The maximum number of disk drives in your system 0x76c: BSIO Entry point to FMS disk sector I/O routines 0x772: BSIOR Entry point to the FMS disk handler 0x7cb: DFMSDH Entry point to a 21-byte FMS device (disk) handler 0x7e0: DINT FMS initialization routine 0x8ab: DFMOPN OPEN routines 0x9cc: DFMPUT PUT byte routines 0xa1f: WTBUR Burst I/O routines 0xabf: DFMGET GET byte routines 0xb15: DFMCLS IOCB CLOSE routines 0xba7: DFMDDC Start of the device-dependent command routines 0xbd9: XRENAME RENAME a file 0xc32: XDELETE DELETE a file 0xc7c: XLOCK, LOCK and UNLOCK files 0xcba: XPOINT BASIC POINT command 0xd03: XNOTE BASIC NOTE command 0xd18: XFORMAT Format the entire diskette 0xdad: LISTDIR List the disk directory 0xe9e: FNDCODE File name decode 0xf0a: FDSCHAR Store the file name characters that result from the file name decode routines 0xf21: SFDIR Directory search routines 0xf94: WRTNXS Write data sector routine 0x100f: RDNXTS Read data sector routine 0x106e: RDDIR Read and write directory sector routines 0x108b: RDVTOC Read or write the volume table of contents (VTOC) sectors 0x10c5: FRESECT Free sector(s) routine 0x1106: GETSECTOR Get sector routine 0x1164: SETUP SETUP -- initialization of the FMS parameters 0x120a: WRTDOS Write new DOS 0x12b5: ERRNO Start of the FMS error number table 0x1381: FCB Start of the FMS File Control Blocks (FCB's) 0x1401: FILDIR File directory 0x1501: ENDFMS Disk directory (VTOC -- Volume Table Of Contents) buffer 0x159d: DUPFLG Flag to test if DUP is already resident in memory 0x159e: OPT Used to store the value of the disk menu option chosen by the user 0x159f: LOADFLG If this location reads 128 0x15a4: SFLOAD Routines to load a MEM.SAV file if it exists. 0x170b: MEMLDD Flags that the MEM.SAV file has been loaded. 0x179c: INISAV vector save location for DOSINI. Entry point to DOS on a call from BASIC 0x179e: MEMFLG Flag to show if memory has been written to disk using a MEM.SAV file 0x1912: CLMJMP Test to see if DOS must load MEM.SAV from disk 0x1920: LMTR Test to see if DOS must load MEM.SAV 0x1939: LDMEM MEMSAVE load routines (for the MEM.SAV file) 0x1976: INITIO DUP.SYS warmstart entry 0x1a23: ISRSIR Start of the serial interrupt ready service routines in DUP.SYS 0x1da4: LINE 80 ($50) byte line buffer 0x1df4: DBUF 256 ($100) byte data buffer for COPY routines 0x1f0f: DMENU Disk menu screen display data is stored here 0x2075: DOSOS Start of the DOS utility monitor 0x2139: DIRLST Directory listing 0x21c9: DELFIL Delete a file 0x2637: RENFIL Rename a disk file routines 0x2680: FMTDSK Format the entire disk 0x26ee: STCAR Start a cartridge 0x274c: BRUN Run a binary file at the user-specified address 0x27d9: WBOOT Write DOS/DUP files to disk 0x28f3: TESTVER2 Test for version two DOS 0x291a: LDFIL Load a binary file into memory 0x2970: LKFIL, Lock and unlock files on a disk 0x29c2: DDMG Duplicate a disk 0x2d08: DFFM Duplicate a file 0x2f2e: SAVFIL Save a binary file 0xbda7: SIN Calculate SIN(FR0) 0xbdb1: COS Calculate Cosine (FR0) with carry 0xbe77: ATAN Calculate Atangent using FR0 0xbee5: SQR Calculate square root (FR0) with carry 0xd000: HPOSP0 (W) Horizontal position of player 0 0xd001: HOPSP1 (W) Horizontal position of player 1 0xd002: HPOSP2 (W) Horizontal position of player 2 0xd003: HPOSP3 (W) Horizontal position of player 3 0xd004: HPOSM0 (W) Horizontal position of missile 0 0xd005: HPOSM1 (W) Horizontal position of missile 1 0xd006: HPOSM2 (W) Horizonal position of missile 2 0xd007: HPOSM3 (W) Horizontal position of missile 3 0xd008: SIZEP0 (W) Size of player 0 0xd009: SIZEP1 (W) Size of player 1 0xd00a: SIZEP2 (W) Size of player 2 0xd00b: SIZEP3 (W) Size of player 3 0xd00c: SIZEM (W) Size for all missiles 0xd00d: GRAFP0 (W) Graphics shape for player 0 written directly to the player graphics register 0xd00e: GRAFP1 (W) Graphics for player 1 0xd00f: GRAFP2 (W) Graphics for player 3 0xd010: GRAFP3 (W) Graphics for player 3 0xd011: GRAFM (W) Graphics for all missiles 0xd012: COLPM0 (W) Color and luminance of player and missile 0 (704) 0xd013: COLPM1 (W) Color and luminance of player and missile 1 (705) 0xd014: COLPM2 (W) Color and luminance of player and missile 2 (706) 0xd015: COLPM3 Color and luminance of player and missile 3 (707) 0xd016: COLPF0 Color and luminance of playfield zero (708) 0xd017: COLPF1 Color and luminance of playfield one (709) 0xd018: COLPF2 Color and luminance of playfield two (710) 0xd019: COLPF3 Color and luminance of playfield three (711) 0xd01a: COLBK Color and luminance of the background (BAK) 0xd01b: PRIOR (W) Priority selection register 0xd01c: VDELAY (W) Vertical delay register 0xd01d: GRACTL (W) Used with DMACTL (location 54272 0xd01e: HITCLR (W) POKE with any number to clear all player/missile collision registers 0xd01f: CONSOL (W/R) Used to see if one of the three yellow console buttons has been pressed (not the RESET button!) 0xd200: AUDF1 (W) Audio channel one frequency 0xd201: AUDC1 (W) Audio channel one control 0xd202: AUDF2 (W) Audio channel two frequency 0xd203: AUDC2 (W) Audio channel two control 0xd204: AUDF3 (W) Audio channel three frequency 0xd205: AUDC3 (W) Audio channel three control 0xd206: AUDF4 (W) Audio channel four frequency 0xd207: AUDC4 (W) Audio channel four control 0xd208: AUDCTL (W) Audio control 0xd209: STIMER (W) Start the POKEY timers (the AUDF registers above) 0xd20a: SKREST (W) Reset BITs 5 - 7 of the serial port status register at 53775 to one 0xd20b: POTGO (W) Start the POT scan sequence 0xd20d: SEROUT (W) Serial port data output 0xd20e: IRQEN (W) Interrupt request enable 0xd20f: SKCTL (W) Serial port control 0xd300: PORTA (W/R) Reads or writes data from controller jacks one and two if BIT 2 of PACTL (location 54018) is one 0xd301: PORTB (W/R) Port B 0xd302: PACTL (W/R) Port A controller (see 54016 above) 0xd303: PBCTL (W/R) Port B controller 0xd400: DMACTL (W) Direct Memory Access (DMA) control 0xd401: CHACTL (W) Character mode control 0xd402: DLISTL/H Display list pointer 0xd404: HSCROL (W) Horizontal scroll enable 0xd405: VSCROL (W) Vertical scroll enable 0xd407: PMBASE (W) MSB of the player/missile base address used to locate the graphics for your players and missiles (the address equals PMBASE * 256 0xd409: CHBASE (W) Character base address 0xd40a: WSYNC (W) Wait for horizontal synchronization 0xd40b: VCOUNT (R) Vertical line counter 0xd40c: PENH (R) Light pen horizontal position (564) 0xd40d: PENV (R) Light pen vertical position (565) 0xd40e: NMIEN (W) Non-maskable interrupt (NMI) enable 0xd40f: NMIRES (W) Reset for NMIST (below) 0xd800: AFP ASCII to Floating Point (FP) conversion 0xd8e6: FASC FP value to ASCII conversion 0xd9aa: IFP Integer to FP conversion 0xd9d2: FPI FP to integer conversion 0xda44: ZFR0 Clear FR0 at 212 to 217 ($D4-$DB) by setting all bytes to zero 0xda46: ZF1 Clear the FP number from FR1 0xda60: FSUB FP subtract routine 0xda66: FADD FP addition routine 0xdadb: FMUL FP multiplication routine 0xdb28: FDIV FP division routine 0xdd40: PLYEVL FP polynomial evaluation 0xdd89: FLD0R Load the FP number into FR0 from the 6502 X 0xdd8d: FLD0P Load the FP number into FR0 from user routine 0xdd98: FLD1R Load the FP number into FR1 from the 6502 X 0xdd9c: FLD1P Load the FP number into FR1 from user program 0xdda7: FST0R Store the FP number into the 6502 X 0xddab: FST0P Store the FP number from FR0 0xddb6: FMOVE Move the FP number from FR0 to FR1 0xddc0: EXP FP base e exponentiation 0xddcc: EXP10 FP base 10 exponentiation 0xdecd: LOG FP natural logarithm 0xded1: LOG10 FP base 10 logarithm 0xe400: EDITRV Screen Editor (E 0xe410: SCRENV Display handler (television screen) (S 0xe420: KEYBDV Keyboard handler (K 0xe430: PRINTV Printer handler (P 0xe440: CASETV Cassette handler (C 0xe450: DISKIV Disk handler initialization vector 0xe453: DSKINV Disk handler (interface) entry 0xe456: CIOV Central Input/Output (CIO) utility entry 0xe459: SIOV Serial Input/Output (SIO) utility entry point 0xe45c: SETVBV Set system timers during the VBLANK routine 0xe45f: SYSVBV Stage one VBLANK calculations entry 0xe462: XITVBV Exit from the VBLANK routine 0xe465: SIOINV SIO utility initialization 0xe468: SENDEV Send enable routine 0xe46b: INTINV Interrupt handler initialization 0xe46e: CIOINV CIO utility initialization 0xe471: BLKBDV Blackboard mode entry 0xe474: WARMSV Warmstart entry point (RESET button vector) 0xe477: COLDSV Coldstart (powerup) entry point 0xe47a: RBLOKV Cassette read block routine entry 0xe47d: CSOPIV Cassette OPEN for input vector 0xe480: VCTABL RAM vector initial value table 0xe4a6: CIOORG Addresses for the Central Input/Output routines (CIO) 0xe4a6: CIOINT is the CIO initialization routine called by the monitor on powerup 0xe569: CIREAD; process the CIO commands for read and write 0xe6d5: INTORG Addresses for the interrupt handler routines 0xe6f3: PIRQ; IRQ interrupt service routines start here 0xe7b4: PNMI; the NMI handler 0xe7d1: SYSVBL; the VBLANK routines start here 0xe912: SETVBL; subroutines to set the VBLANK timers and vectors 0xe944: SIOORG Routines for the Serial Input/Output (SIO) routines 0xea6b: SEND; is the SIO send buffer routine entry 0xea90: ISRODN, is the serial output ready IRQ vector 0xead1: ISRTD; is the serial output complete IRQ vector 0xeb11: ISRSIR; is the serial input ready IRQ vector 0xeb84: CASENT; is the start of the cassette handling code SIO subroutine to set baud rate 0xeca7: COMPUT; is the subroutine to calculate baud rate using the POKEY frequency registers and the VCOUNT timer 0xedea: DSKORG Routines for the disk handler 0xee78: PRNORG Routines for the printer handler 0xef41: CASORG Routines for the cassette handler 0xf0e3: MONORG Routines for the monitor handler 0xf11b: RESET; the RESET button routine starts here 0xf281: HARDI, the start of the hardware initialization routines 0xf294: OSRAM; the start of the OS RAM initialization and setup routines 0xf2cf: BOOT; the entry point for the disk boot routine 0xf2ed: DOBOOT; the disk boot routine activation 0xf37e: DOPEN; the entry point for the reinitialization of disk software 0xf3e4: KBDORG Routines for the display and keyboard handler 0xf63e: EGETCH Like the BASIC INPUT command 0xf6a4: EOUTCH This routine puts the character currently in the accumulator onto the screen in the next print location 0xf6dd: KGETC2 Beginning of the keyboard handler 0xf6e2: KGETCH This routine waits for a key to be pressed and returns its value to the accumulator (6502 register A) 0xfbac: SCROLL The screen scroll routine starts here 0xfcfc: DRAW Screen draw routines begin here 0xffbe: PIRQQ Subroutines to test the acceptance of the last key pressed and to process the debounce delay routines start here 0xfff8: CHKSUN If PEEK here returns 255, then you have the older OS ROM(s)