www.cpcalive.com
Cliquer ici pour la documentation française
Pulsar aquí para la documentación en español
* CpcAlive V1.08M *
* DOCUMENTATION (V0.3) *


notes:
- This documentation relates about information necessary to use the CpcAlive emulator. A demonstration, utility softwares, a Z80 assembler, a X86 assembler, documentations about Cpc exploitation and Bios/Dos interruptions are available on the internet site: www.cpcalive.com
- This documentation uses two types of hexadecimal values notation. The first notation adds the sign "&" in front of the value, ex:&3F. The second notation adds the letter "h" behind the value, ex:3Fh.

TABLE OF CONTENTS

 I - Presentation and installation of the CpcAlive emulator
II - CpcAlive commands syntax:
    CpcAlive [input_files[:X]] [CpcAlive commands] [Cpc commands] [>output_file]
    - 1 - CpcAlive Input files
        - 1a - Loading virtual diskettes files (.DSK) -
         - 1b - Loading Cpc roms files -
        - 1c - Loading intel hex files  -
        - 1d - Loading CpcAlive commands files
        - 1e - Loading text files (KeyBoard simulation)
        - 1f - Loading binary files
    - 2 - Cpc commands from the Dos command line
     - 3 - CpcAlive Output_files
III - CpcAlive commands from the Cpc basic interpreter
IV - ACCENTUED CHARACTERS
V - BIOS AND DOS INTERRUPTIONS ACCESS TROUGH Z80
VI - X86 ENVIRONMENT
VII - UTILITY SOFTWARES
     - 1 - CreaDisc: create a virgin virtual diskette. (data formatted)
    - 2 - AniCrea.exe: create a FLI animation file
    - 3 - Fli2Gif.exe: read a FLI animation file
    - 4 - Floppy boot CpcAlive
    - 5 - CD boot CpcAlive


                                                                                                                                                                                                                      

I - Presentation and installation of the CpcAlive emulator

CpcAlive is a computer Amstrad CPC 6128 emulator. One of the interest of this emulator is to create graphic animation files from screen images.

 CpcAlive Specificities:

* X86 programmation environment (16Mo)
* Bios and Dos interruptions access trough Z80 instructions
* outputs screens in BMP and FLI animation format
* pallets 262144 colors
 * emulation keyboard starting from a text file
* management keyboard automaticly integrated to the PC keyboard system.
* the Cpc softwares can beings used like filters and beings integrated in a .BAT file.  (exit the emulator with BASIC instruction)
* possibility to treat from the Cpc BASIC interpreter any file present on the hard drive or another support.
* include a Z80 debugger.
* compatiblity: - Dos,Windows 95/98/2000/Me/XP
                      - processors 386 and more.

After the installation, you can launch the emulator from the Windows desktop. To launch the emulator from the Dos command line, use the "Start" button of Windows, an click on "All the programs", then "CpcAlive". A menu is posted including, inter alia, an icon to launch the emulator, an icon to launch the Dos system for Windows XP and an icon to launch the Dos system for Windows 95 and 98. The various utility programs provided with the CpcAlive emulator are accesssibles starting from the Dos command line.

 = Icon to launch CpcAlive
= Icon to launch the "Windows Dos" system.

Notes:
    - Amstrad roms ares copyrighted, you cannot thus normally use CpcAlive only if you have an Amstrad Cpc 6128 computer in a position to function.
    - colors PAPER and PEN 1 were modified with initialization for ergonomic reason  (less tiring for eyes).


II - CpcAlive commands syntax:

CpcAlive [input_files[:X]] [CpcAlive commands] [Cpc commands] [>output_file]
or
! [input_files[:X]] [CpcAlive commands] [Cpc commands] [>output_file]

- 1 - CpcAlive Input files
~~~~~~~~~~~~~~~~~~~~~~~
Files recognized by the emulator are:

 Virtual diskette with format DSK     (see chapter - 1a -)
Cpc rom files                                 (see chapter - 1b -)
Intel hex files                                 (see chapter - 1c -)
CpcAlive command files                 (see chapter - 1d -)
Text documents                             (see chapter - 1e -)
Binary files                                    (see chapter - 1f -)

 To load a file starting from the Dos command line:
CpcAlive filename[:X]
It is also possible to use the syntax: ! filename[:X]

The letter represented by the character "X" is optional, it depends on the type of file to load. It will be called "marker" and will have to be typed in capital letter.
note: don't put spaces betwen the file name and the marker.

To load a file starting from a CpcAlive command file:
filename[:X]

To load a file starting from the Cpc BASIC interpreter:
|INPUT,"filename[:X]"[,@er%]

The error return parameter @er% is facultatif. If it is put, the significance of the values recovered in the variable er% are:
0 = ok
1 = error number parameters
2 = way not found
(don't forget initialize er% at the program beginning or before the command)

         ex:    10 er%=0
                 20 |INPUT,"Disc.dsk:A",@er%
                 30 if er%<>0 then PRINT"ERROR":STOP

It is possible to put several file names at the continuation. They must be separated by a space character. In this case, the error code er% will relate to the last file mentioned. The vertical bar present in front of the command INPUT is obtained by actuating in same time the key [AltGr] and the key [6] located in top of the keyboard.

- 1a - Loading virtual diskettes files (.DSK) -
Make follow the file name of the ":A" or ":B" markers to choose the Cpc drive destination.(drive A by defect)

example starting from the Dos command line:
! disc.dsk:A
 example starting from a CpcAlive command file:
disc.dsk:A
example starting from the Cpc BASIC interpreter:
|input,"disc.dsk:A"

This command launch the emulator and load the virtual diskette "disc.dsk" in drive A.


- 1b - Loading  Cpc roms files -

There is three 16Kb roms blocks in the Cpc 6128 (48Ko). One of these blocks contains the operating system which is connected in zone 0 to 03FFFh (lower rom). The two other blocks (BASIC and disc system) are connected in the zone 0C000h to 0FFFFh (higher roms). The system can exploit in this zone 252 blocks of 16Ko each one. An interesting characteristic of these roms is that they can receive BASIC programmable instructions (Resident System eXtension).

To load a rom file in the emulator, make follow the file name by the ":R" marker. CpcAlive will seek the first area available. The file can be binary or intel hex formated.

Loading starting from the Dos command line:
! Z80ROM.ROM:R
Loading starting from a CpcAlive command file:
Z80ROM.ROM:R
Loading starting from the Cpc BASIC interpreter:
|INPUT, "Z80ROM.ROM:R":call 0

If it is necessary to have a fixed area number, you can replace the letter "R" with an area number (0<area number <256).
example starting from the Dos command line:  ! Z80ROM.ROM:R:10

Roms will be recognized by the Cpc system only after a rebootstrapping for example with a CALL 0 or by actuating keys [Ctrl][Alt][Home] in the same time. The emulator takes RSX instructions with all highers roms. The areas numbers used by the Cpc system are 0 for BASIC rom and 7 for DISC rom. The X86 modules (see chapter "X86 Environment") with mnemonics use also Z80 roms sites. The highers roms with a specific site number must be loaded before the X86 modules. The best way is to indicate them at the beginning of the command file ROM.INI located in the principal repertory.

note: - All markers must be write with capital letters.

 Sample coding of an Amstrad Cpc Rom containing programmable basic instructions (Resident System eXtension)


- 1c - Loading intel hex files  -

The Intel Hex Object Format is line oriented and uses only printable ASCII characters.

Intel Hex line:
:LLAAAA00DDDD   ; ':' = start character (colon)
                                ; LL = block size (2 hex digits)
                                ; AAAA = starting adress (4 hex digits)
                                ; 00 = record type (00)
                                ; DDDD = data bytes (a pair of hex digits for each byte of data)

file example:
:18A600000109A62111A6C3D1BC15A6C31EA6C335A6000000004F5049A2
:18A61800D8495049D800DD5603DD5E02DD4605DD4E043E0C4052DD7E97
:18A6300000404810C9D5DD5603DD5E02DD4605DD4E043E0D40524048AD
:07A6480010D11213AF12C97B
:00000001FF

In this example, the first line contains 018h data bytes (01h,09h,0A6h... 049h) which will be loaded starting from the address 0A600h. The check sum of the line is equal to 0A2h. The check sum (2 hex digits) normally present at the end of a standard intel hex line is not obligatory with CpcAlive. Note the record type equal to 1 indicating the last line of the file. This line is not necessary with files loaded by the emulator.

Loading in rom:

 To load an intel hex file in rom, make follow the file name by the ":X" marker where X represent the rom recipient number.

Example for loading in rom number 10:
starting from the Dos command line:
!  FILENAME.HEX:10
starting from a CpcAlive command file:
FILENAME.HEX:10     for loading in rom number 10
 starting from the Cpc BASIC interpreter:
|input,"FILENAME.HEX:10"

If the destination rom does not exist, CpcAlive create it. In this case it is possible to use the :R marker (see chapter "Loading Cpc roms files")


Loading in ram:

 The 6128 has a 128 KB memory (RAM) divided into eight blocks of 16 KB each one, numbered from 0 to 7. Only four blocks can beings connected simultaneously.

 Table showing ram blocks positioning in foncion of the configuration type:
Value on port &7F    blocks position
                &C0            0,1,2,3            <= standard Cpc configuration memory
                &C1            0,1,2,7
                &C2            4,5,6,7
                &C3            0,3,2,7
                &C4            0,4,2,3
                &C5            0,5,2,3
                &C6            0,6,2,3
                &C7            0,7,2,3

The Cpc system exploits only the first configuration. In this configuration block 0 occupies memory space 0 to 03FFFh, block 1 space 04000h to 07FFFh, block 2 space 08000h to 0BFFFh and block 3 space 0C000h to 0FFFFh. The screen exploits block 3. The higher part of block 2 contains the system variables. The lower part of block 0 is used by the system. The BASIC programs are loaded by the system starting from the address 0170h. The binary data can beings loaded starting from the address defined using the Basic instruction "MEMORY". If they are executable programs, they could be called with the instruction "CALL".

To load an intel hex file in ram, make follow the file name by the ":X" marker where X represents the ram recipient configuration type.

Valids hexadecimal values for loading in RAM are:
0C0h, 0C1h, 0C2h, 0C3h, 0C4h, 0C5h, 0C6h and 0C7h

By defect, the loading is done in RAM with 0C0h configuration.

 example starting from the Cpc BASIC interpreter
|input,"FILENAME.HEX"
In this case, the file "file.hex" is loaded with the standard Cpc configuration memory.

notes:
- It is possible to see the Cpc memory with CpcAlive with the command |DEBUG,&f from the BASIC interpreter.
- Put values in RAM blocks 0,1,2 ou 3 before the Cpc system initialization is useless because this blocks are cleared with starting. To put values in RAM from the Dos command line, the system could be launched and put in sleeping mode previously.
- All markers must be write with capital letters.


                                                                                                                                                                                                                       
note: The Z80 assembler "tasm" which generates intel hex files is available on the internet site: www.cpcalive.com
                                                                                                                                                                                                                       


- 1d - Loading command files

The intern emulator valid commands starting from the Dos system command line or a CpcAlive command file are:

CpuFast                    ; set maximum speed
CpuSlow                   ; set normal speed (speed of the original Cpc computer)
Sleep                        ; put the emulator on sleeping state [AltGr][S]
Exit                          ; to leave emulator [Ctrl][Alt][End]
ROM=X                   ; select ROM X (256 for the Cpc bios)
RAM=X                   ; select RAM X type
                                ; see chapter II paragraph - 1c - "Loading in ram"
                                ; for ram configuration values.
:LLAAAA00DDDD   ; loading data. (Intel Hex line)
CommandEnd (or EndCde) ; indicate the end of a command file. (facultatif)
Keyboard                  ; going from the COMMAND mode to the KEYBOARD mode. After this command, the file will not be interpreted any more like a command file but like a text file . Use the keyword  "|Command" to go back in COMMAND mode.

The commands CommandEnd, EndCde and KeyBoard restore the effective Cpc memory configuration at the beginning of the command file.

example starting from the Dos command line
To select the BIOS rom and poke the value 2 in 0B13h adress (start screen mode) and select slow speed emulation:

! ROM=256 :010B130002 CpuSlow

Don't forget spaces between commands.

If a CpcAlive command is not reconized, this command and the rest of the line is interpreted like a Cpc command. You can by this way adding one or more Cpc commands at the end of the line. (Only from the Dos interpreter. From CpcAlive commands files, use the "keyboard" command).

example:

! ROM=256 :010B130002 CpuSlow PRINT"OK"

note:
- put values in RAM blocks 0,1,2 ou 3 before the Cpc system initialization is useless because this blocks are cleared with starting. To put values in RAM from the Dos command line, the system could be launched and put in sleeping mode previously.


CpcAlive command files:

These files are intended, as their name indicates it, to command the emulator from a file. This file must start with "CDE:" or "CMD:" sequence without guillemets (header).

Loading starting from the Dos command line:
! FILENAME.CMD
Loading starting from a CpcAlive command file:
FILENAME.CMD
Loading starting from the Cpc BASIC interpreter:
|INPUT, "FILENAME.CMD"
                  
example 1:
Select the BIOS rom and poke the value 2 in 0B13h adress (start screen mode) and select slow speed:

CMD:                ; header
ROM=256        ; select rom bios
:010B130002    ; poke the value 2 in 0B13h adress (start screen mode)
CpuSlow          ; speed selection
CommandEnd   ; close the command file

example 2:
CMD:                ; header
ROM=256        ; select rom bios
:010B130002    ; poke the value 2 in 0B13h adress (start screen mode)
CpuSlow          ; speed selection
Keyboard         ; swap in keyboard mode
                       ; (starting from here each character is transmitted
                       ; directly to the Cpc keyboard manager)
PRINT"OK"

example 3:
PRINT"OK1"
|COMMAND    ; going from the KEYBOARD mode to the COMMAND mode.
ROM=256        ; select rom bios
:010B130002    ; poke the value 2 in 0B13h adress (start screen mode)
CpuSlow          ; speed selection
Keyboard         ; swap in keyboard mode
                       ; (starting from here each character is transmitted
                       ; directly to the Cpc keyboard manager)
PRINT"OK2 "


It is also possible to load from a CpcAlive command file the following types of files: virtual diskettes with format DSK , Cpc rom files , intel hex files , command files , text documents and binary files . The command files overlap is authorized with the limits of 15 files maximum (text files included). A good example is the ROM.INI file which is a command file intended for the emulator initialization. It is from this one that for example the Cpc roms are loaded. Note the separator ';' for comments. (!do not use the command "KeyBoard" in the file ROM.INI).The command file CPC.INI located in the CpcAlive repertory is a user file which can receive configuration commands.

- 1e - Loading text files (KeyBoard simulation)

If the file type is not recognized by CpcAlive as being one of files detailed higher, CpcAlive considers that it is a text file. CpcAlive treats these files like this: each character of the document is read and sent to the Cpc keyboard manager. You can thus, for example, transmit by this function a BASIC file with text format or pilot a software running into the emulator.

Loading from the Dos command line:
! example.bas
Loading from a CpcAlive command file:
example.bas
Loading from the Cpc BASIC interpreter:
|input,"example.bas"

These commands load the text named "exemple.bas" through the Cpc keyboard manager. This file must be in text format. In this example it must be in the CpcAlive directory or a path directory. If the file does not exist, the chain "exemple.bas" will be transmitted to the Cpc keyboard manager and will probably cause a "Syntax error" message.

example starting from the Cpc BASIC interpreter:
mode 2
10 |Input,"FILE_ID.DIZ"
20 line input a$:if a$="" then |STOP:end else goto 20
run

This example load the document "FILE_ID.DIZ" until it meet one blank line. The command |STOP close the file.

The text files overlap is authorized with the limits of 15 files maximum (command files included).
It is also possible to load texts in the CpcAlive emulator with the Windows XP copy/paste function. See instructions.


- 1f - Loading binary files

It is possible to use the marker ":D" (like 'D'atas) to load data in the Cpc memory by using the following syntax:

from the Cpc BASIC interpreter:
|INPUT,"filename:D,block lenght,address block in file,load address in cpc memory"
(think to protect the loaded block with the command: MEMORY load_address - 1)
from a CpcAlive command file:
filename:D,block lenght,address block in file,load address in cpc memory

It is thus possible to treat any type of file. The example below load an image BMP (option OS/2 format, 16 colors, 180*100 max.) and posts it on the Cpc screen.

10 memory &3FFF:adr=&4000
20 ximg=0:yimg=0:nameimg$="image.bmp":' <<<< X,Y,IMAGE NAME
30 |input,nameimg$+":D,&4100,0,&4000"
40 if peek(adr+&E)+256*peek(adr+&F)<>12 then mode 2:?"OS/2 format only accepted":end
50 x=peek(adr+&18)+256*peek(adr+&19)
60 if x<>4 then mode 2:?"16 colors in image only accepted.":end
70 mode 0:x=0:for i=0 to 45 step 3:|ink,x,peek(adr+&1C+i),peek(adr+&1B+i),peek(adr+&1A+i):x=x+1:next
80 largeur=peek(adr+&12)+256*peek(adr+&13)
90 hauteur=peek(adr+&14)+256*peek(adr+&15)
100 reste=largeur mod 2:x=int(largeur/2)+reste:while x mod 4 <> 0:x=x+1:wend:larbloc=x
110 adr=adr+peek(adr+&A)+256*peek(adr+&B):'adresse image dans fichier
120 for i=0 to hauteur*4 step 4:x=0
130 for j=adr to adr+(int(largeur/2)+reste)
140 pencil=(peek(j) and &F0)/16:plot ximg+x,yimg+i,pencil:plot ximg+x,yimg+i+2,pencil:x=x+4
150 pencil=peek(j) and &F:plot ximg+x,yimg+i,pencil:plot ximg+x,yimg+i+2,pencil:x=x+4
160 next j:adr=adr+larbloc:next i
run


The ":D" marker alone following the file name indicates to the emulator that it must transmit the value in decimal format of each byte of the file through the Cpc keyboard manager.This function has been developed to easily treat datas from a file with the Cpc BASIC interpreter.

Here, a small program whose function is reading some bytes of ROM.INI file and print them in hexadecimal format:

10 mode 2:window#0,1,80,2,25:window#1,1,80,1,1
20 |Input,"ROM.INI:D"
30 for i=0 to 100
40 input#1,a:Print hex$(a,2)" ";
50 next i
60 |STOP
run


The command |GO, "numerical chain"[,@er% ] move the file pointer.
In this case, "chain" represent the displacement value compared to the file beginning. The error return parameter @er% is facultatif. If it is put, the values significance recovered in the variable er% are:
0 = ok
1 = error
(don't forget to initialize er% at the program beginning or before the command)

example starting from the Cpc BASIC interpreter:
|GO,"&100"

Moves the file pointer to the position &100. The maximum value is &FFFFFFFF. The file pointer position can be write with decimal format.


 - 2 - Cpc commands from the Dos command line
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The Cpc commands must always be placed at the last of the command line.

ex: ! PRINT"ok"
Launch the emulator and places the command PRINT"ok" through the Cpc keaboard manager.

Particular case:
The '|' character is a Dos command. CpcAlive uses thus a substitution character which is the '§' than you can obtained with the [ALT][245] keyboard sequence from the Dos command line. (If you obtain another character than '§' on your screen it is not important. The most important is the [ALT][245] keyboard sequence to obtain the ascii character number 245 in the Dos command line)

ex: ! §DISC
Launch the emulator and place the command |DISC in Cpc keyboard manager.

There are other reserved characters by Dos like "<" or ">" which can't be used for Cpc commands from the Dos command line. For more information read the Dos system documentation.


- 3 - CpcAlive Output files
~~~~~~~~~~~~~~~~~~~~~~~~~~
By defect the Cpc printing output is done in file CPC.PRN located in CpcAlive directory. It is possible to change the name of the output file starting from the Dos command line by adding the character '>' to the end of the line followed the desired file name.

example:
! PRINT#8, "OK"                 register word "OK" in the file Cpc.prn
! PRINT#8, "OK">test.prn    register word" OK "in the file test.prn

Only one character ' > ' before the output file name indicates to the Dos system that if the output file name already exists, this file will be recreate virgin before receiving datas. (the old one output file with the same name being delete without notice... warning). Two characters ' > > ' before the output file indicates to the Dos system that it must preserve the file and put new data to be followed. (There does not exist at time equivalent CpcAlive command from the Cpc BASIC interpreter)

example:
! PRINT#8, "OK1":§Exit>test.prn         register word "OK1"in the file test.prn
! PRINT#8, "OK2":§Exit>>test.prn       register word "OK2"follow in the file test.prn

The result in the file test.prn gives:
OK1
OK2

It is possible to change the output file name from the Cpc Basic interpreter by typing the following command:  |OUTPUT, "FILENAME"[,@er% ]

The error return parameter @er% is facultatif. If it is put, the significance of the values recovered in the variable er% are:
0 = ok
1 = error number parameters
3 = way not found
4 = no more handle available
5 = refused access
(don't forget to initialize er% at the beginning of the program or before the command)

A small program which redirect the CATalogue output towards the output file:
10 POKE &BB5C,PEEK(&BD2D):POKE &BB5B,PEEK(&BD2C)
20 CAT
30 CALL &BD37:|DISC
RUN

note: The file CPC.PRN is emptied with each launching of the emulator.

III - CpcAlive commands  from the Cpc basic interpreter:

The CpcAlive commands starting from the interpreter BASIC must be preceded by the vertical bar " | ".

|CpuFast                    = maximum speed
|CpuSlow                   = normal speed (speed of the Cpc computer)
|Sleep                        = put the emulator on sleeping mode [AltGr][S]
 |Sleep,"message"        = set sleeping mode with message
|Exit                          = to leave the emulator [Ctrl][Alt][End]
 |Exit,"message"          = leave the emulator with message
|Command                 = going from the KEYBOARD mode to the COMMAND mode.
                                   (see chapter II paragraph - 1d - )
|INPUT, "file_name[:X]"[,@er% ]
                                 = see chapter II paragraph - 1 -
|STOP                       = see chapter II paragraph - 1e -
|GO, "numerical chain"[,@er% ]
                               = see chapter II paragraph - 1f -
|OUTPUT, "output_file"[,@er% ]
                                = see chapter II paragraph - 3 -
|OUTASCDOS          = see chapter IV
|OUTASCWIN          = see chapter IV
|OUTASCOFF           = see chapter IV
|PRINT, "chains"       = output character string towards output_file.
                                   (Command equivalent to the command PRINT#8,"chains";)
|LPRINT, "chains"     = output character string towards output_file followed by a carriadge return.
                                   (Command equivalent to the command PRINT#8,"chains")
|INK,PEN,R,G,B       = change PEN color. Letters R,G,B représents Red,Green and Blue values (0 to 255)
                                   ex: |INK,0,0,255,0 (change PAPER color)
                                   ex: |INK,1,255,0,0 (change PEN 1 color)
|INKRESTORE         = restore originals Cpc inks.
|INKCPC                  = standard cpc inks
|INKSOFT                = CpcAlive inks (inks by defect)
                                   The pallet is the same as the standard pallet Cpc but with less
                                   luminosity, and values Paper and PEN 1 are modified with starting.
|OBMP, "nom_de_fichier"[,@er% ]
                                = create a file image of the Cpc screen (BMP format).
                                    - see |OUTPUT command for error codes significance.
|DEBUG,adresse       = launch the debugger when the Z80 processor meet the specified adress.
|DEBUGOFF            = stop the debugger
|DUMP,adress           = initialize the dump memory first address of the debuggor
CALL 0                    = initialize the Cpc system [Ctrl][Alt][Home]


IV - ACCENTUED CHARACTERS
See french or spanish documentation


V - BIOS AND DOS INTERRUPTIONS ACCESS TROUGH Z80

Bios and Dos interruptions are accessible with CpcAlive specifics opcodes through the emulated Z80 microprocessor and a correspondence between the Z80 and X86 registers. The table below indicates the correspondence of the registers established between the two processors:
Z80 registers      X86 registers
F                 >   Flags
A                 >   AL
BC               >   CX
DE               >   DX
HL               >   BX
IX                >   SI
IY                >   DI

CpcAlive adds registers to the Z80 named AH, BP, DS and ES corresponding to the X86 processors registers, and new opcodes Z80.
Example:
opcode:             mnemonics:     function:
040h, 052h        LD AH, A           load the value of register A in pseudo register AH
040h, 05Bh        LD A, AH          load the value of pseudo register AH in register A
040h, 048h, xx    INT(xx)             call interruption number xx

example of macros (here for the assembler 8 bits tasm)
# define LD_AH_A         db 040h \ db 052h
# define LD_A_AH         db 040h \ db 05Bh
# define INT(xx)             db 040h \ db 048h \ db xx

example:
; ** OUTPUT PIXEL THROUGH INT 010H **
OutPix:     ld de, 12                 ; coordinate Y
                ld bc, 24                 ; coordinate X
                ld a, 0Ch                 ; FUNCTION 0CH = WRITE A GRAPHIC POINT
                LD_AH_A              ; load the value of register A in
                                              ; pseudo register AH
  &nb