Programming - High-quality procedure for converting ZX images to ASCII.

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(C) KAPsoft '2000
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              ON THE QUESTION...

   In my short article I tried
highlight some issues that
encountered recently. Mostly
This material is intended for a programmer,
but it would do well for others to read him too.

              ...ABOUT CONVERSION

   InDeja Vu #08there was an article about conversion
SCREEN's to text files. The idea was that
kova: counting the number of included
pixels (dots) in a block (8 by 4), and, in
depending on their quantity, we put one or
another symbol.
   I propose a different algorithm.  I'll describe it
briefly its essence. For the block in question
we superimpose in turn all the symbols of the loading
married FONT.  Counting the quantity
matches (either on or off)
hatched pixels). The symbol that
If there are more matches, we put it instead of a block.
We repeat everything for the remaining blocks.
   Yes, this will all work quite well
lazy. But the quality will be better.
   Here is a listing of a program that performs this
what kind of conversion.

DEMO  CALL START
      LD   A,2
      CALL #1601
      LD   A,22
      RST  16
      XOR  A
      RST  16
      XOR  A
      RST  16
      LD   BC,768
      LD   DE,TEXT
      JP   #203C
;
START LD   HL,#4000
      LD   DE,TEXT
      CALL ST1
      LD   HL,#4800
      CALL ST1
      LD   HL,#5000
      JP   ST1
;
ST1   LD   BC,256
LOOP  PUSH BC
      PUSH DE
      LD   DE,15616
      LD   B,96
      XOR  A
      LD   (NUM+1),A
      LD   (NUP+1),A
      DEC  A
      LD   (RAZL+1),A
N_4   PUSH BC
      LD   C,0
      PUSH HL
      LD   A,8
N_2   PUSH AF
      LD   A,(DE)
      XOR  (HL)
      LD   B,8
N_1   RRA
      JR   NC,NO
      INC  C
NO    DJNZ N_1
      INC  DE
      INC  H
      POP  AF
      DEC  A
      JR   NZ,N_2
      LD   HL,NUP+1
      INC  (HL)
RAZL  LD   A,0
      POP  HL
      CP   C
      JR   C,N_3
NUP   LD   A,0
      DEC  A
      LD   (NUM+1),A
      LD   A,C
N_3   POP  BC
      LD   (RAZL+1),A
      DJNZ N_4
NUM   LD   A,0
      ADD  A,32
      POP  DE
      LD   (DE),A
      INC  DE
      POP  BC
      INC  L
      DEC  BC
      LD   A,B
      OR   C
      JR   NZ,LOOP
      RET

   В программе есть  некоторые  интересные
приемчики.
   Например, если у вас в прогах есть  та-
кие строки:
      LD    (МЕТКА),A
      ...
      LDA,(LABEL)
  ...
METKA DEFB 0,
then they can be replaced with:
      LD (METKA+1),A
 ...
METKA LD A,0
 That is. store variables in the text itself
programs.
   The comparison is made using XOR-
bytes and counting included bits.Es-
whether the bits are the same (1-1 or 0-0), then after
XORs are 0, and if different, then 1.
Because we need differences, then we count
zeros with the command JR NC,S.
 In this program, a block is one
familiar place, and comparison is made with the standard
standard SPECTRUM FONT, located
married in ROM.
   This is just an example, a serious program for
to do more universally: various
block sizes, loaded FONT, etc.

              ...ABOUT ARROWS.

   Or more precisely about arrow interfaces. In
of all the "intellectual" in-
interfaces (such that if you press for a long time
joystick in one direction, then speed
cursor - arrows increases) speed
increases in onedirection, and her
reset to initial occurs at any
joystick movement.
   I propose a different algorithm. Speed
changes for four directions separately
but... If the user does not press in any way
direction, then the speed in this direction is
leniya is reset to the initial value.
   Here's the listing:

ORG 30000
ENT
 LD DE,#8080  ;Initial
START HALT  ;coordinates
 LD HL,TABL
 IN A,(#1F)  ;Interrogated the joystick
 BIT 0,A  ;Right ?
PUSH AF
 LD A,#3C
 LD (LOOP),A
 LD A,#51
 LD (SBROS),A
 LD A,#57
 LD (REG),A
      CALL NZ,MOVE   ;Да - двигаемся
      POP  AF
      CALL Z,SBR     ;Нет - сброс
      BIT  1,A       ;Влево ?
      PUSH AF
      LD   A,#3D
      LD   (LOOP),A
      CALL NZ,MOVE
      POP  AF
      CALL Z,SBR
      BIT  2,A       ;Вниз ?
      PUSH AF
      LD   A,#5F
      LD   (REG),A
      LD   A,#59
      LD   (SBROS),A
      CALL NZ,MOVE
      POP  AF
      CALL Z,SBR      BIT  3,A       ;Вверх ?
      PUSH AF
      LD   A,#3C
      LD   (LOOP),A
      CALL NZ,MOVE
      POP  AF
      CALL Z,SBR
      BIT  4,A       ;Огонь - выход
      RET  NZ
      LD   C,D       ;Рисуем точку с
      LD   B,E       ;помощью программы
      PUSH DE        ;ПЗУ по адресу ┐
      CALL #22E5     ; <────────────┘
      POP  DE
      JR   START
;
MOVE  LD   A,(REG)   ;Подпрограмма
      CP   #57      ;перемещения
      LD   A,E
      JR   NZ,NEXT
      LD   A,D
NEXT  LD   C,(HL)
      INC  HL
      LD   B,(HL)
LOOM  CP   C
      JR   Z,SBROS
LOOP  INC  A         ;или  DEC  A
      DJNZ LOOM
REG   LD   D,A       ;или  LD  E,A
      INC  HL
      DEC  (HL)
      JR   NZ,L_1
      LD   (HL),24   ;Время закончи-
      DEC  HL        ;лось - увеличиваем
      INC  (HL)      ;скорость
      INC  HL
L_1   INC  HL
      RET
;
SBROS LD   D,C       ;или  LD  E,C
      JR   CONT
SBR   INC  HL        ;Сброс скорости и
      LD   (HL),1    ;времени на началь-
      INC  HL        ;ные значения.
      LD   (HL),24
      INC  HL
      RET
;
TABL  DEFB 255,1,24  ;Первое - MAX/MIN
      DEFB   0,1,24  ;Второе - скорость
      DEFB   0,1,24  ;Третье - время
      DEFB 175,1,24

   Для упрощения вместо стрелки  использу-
ется точка. Для  того,to run fast
lock, instead of CALL #22E5 put a call
its arrow output procedure.
  To make the point run faster, you can reduce
show the time value, but not in the table, but
in lines LD (HL),24 at the end of procedures MOVE
and SBROS. You can also increase the frequency of calling the process
fools (in this program - once in interruption -
or 50 times per second).

          ...ABOUT MULTITASKING.

   As you know, Intel processors are
we can execute several programs simultaneously
exactly. In reality, of course, they are not
all work at once. Operating system
runs a small piece of one program
us, then a piece of another, a third. And pol-
it seems to the callers that they are all working
at the same time.
   I came up with a (crazy?) idea -
try to create such a system using SPEC-
C.Y. In the first minute of thinking I stood up
problem:HOW TO INTERRUPT THE PROCESSOR AFTER NON-
WHAT TIME IS IT? On PC everything is simple: yes
special interruptions. So this would have sunk
the idea is in vain, if notmy second idea:
IM 2. But it is already used for polling
keyboards, music, etc.
   What can you do, programs for such a system
the topic will have to be written specially. But that's how
they say, if he presses hard (you have to press hard)
children), then they will do it. Moreover, the tra-
takes up about 1% of CPU time. And you-
the call of Mouzon and others is carried out as without
systems, i.e. 50 times per second.
   So, the idea:

    * For each program, a personal
       ny stack.
    * The first one is connected and starts
       first program.
  ┌>* When an interrupt arrives, the
  │  there is a system that saves everything
  │  processor registers on the stack are executed
  │  of the program being used.  She remembers
  │  stack value in a special table
  │  tse. The stack is connected for the next
  │  task, the values of the re-
  │   гистров и адрес запуска(или продол-
  │    жения, если это не запуск).
  │ * Запускается вторая программа.
  └─┘

   Вот листинг :

      ORG  30000
      ENT
DEMO  DI
      LD   HL,KOL+1
      LD   (HL),3
      LD   HL,PROG2
      LD   (29022),HL
      LD   A,#7F
      LD   I,A
      LD   HL,INT
      LD   (#7FFF),HL
      IM   2
      EI
;
PROG1 LD   A,#87
      LD (#5800),A
      LD   A,#7F
      IN   A,(#FE)
      AND  #1F
      XOR  #1F
      JR   Z,PROG1
      DI
      LD   A,63
      LD   I,A
      IM   1
      EI
      RET
;
PROG2 LD   A,#78
      LD   (#581F),A
      JR   PROG2
;
NUMB  DEFB 0
TABL1 DEFB 0,1,0
TABL2 DEFW 0,29000
;
INT   PUSH AF
      LD   A,R
      PUSH AF
      PUSH DE
      PUSH BC
      PUSH HL
      PUSH IX
      PUSH IY
      EX   AF,AF'
      PUSH AF
      EXX
      PUSH DE
      PUSH BC
      PUSH HL
      LD   A,(NUMB)
      LD   E,A
      LD   D,0
      LD   HL,TABL1
      ADD  HL,DE
      LD   A,(HL)
      ADD  A,A
      LD   E,A
      LD   HL,TABL2
      ADD  HL,DE
      LD   A,L
      LD   (KK+2),A
      LD   A,H
      LD   (KK+3),A
KK    LD   (#FFFF),SP
;Здесь можно поставить вызовы ваших
;программ обработки прерываний
;типа     CALL  MYINT
      LD   A,(NUMB)
      INC  A
KOL   CP   3
      JR   NZ,OBHOD
      LD   A,0
OBHOD LD   (NUMB),A
      LD   HL,TABL1
      LD   E,A
      ADD  HL,DE      LD   A,(HL)
      ADD  A,A
      LD   E,A
      LD   HL,TABL2
      ADD  HL,DE
      LD   A,L
      LD   (LL+2),A
      LD   A,H
      LD   (LL+3),A
LL    LD   SP,(#FFFF)
      POP  HL
      POP  BC
      POP  DE
      EXX
      POP  AF
      AX   AF,AF'
      POP  IY
      POP  IX
      POP  HL
POP BC
 POP DE
 POP AF
 SUB 7
 LD R,A
 POP AF
 EI
 RET

   Part DEMO - demonstration. The system itself
starts with NUMB.
 How to use it?
 1. Decide how many programs you need
    but use it.
 2.At the address KOL+1 enter this number:
      LD HL,KOL+1
 LD (HL),N
 3. For each, allocate space for the stack.
 4.At the address STACK+22 of each program
    carry the address of its launch.
 5.Create a table for calling tasks.
    For example:

 TABL1 DEFB 0
 DEFB 1
 DEFB 0
 DEFB 2
 DEFB 0
 Where 0,1,2 are program numbers (corresponding
    definitely 1st, 2nd and 3rd). With such
    table 1 task is assigned 3/5*100=
 =60% time. 2nd and 3rd - by 1/5*100=
 =20% time.
 6.In TABL2 enter the addresses of task stacks:
      TABL2 DEFW STACK0
 DEFW STACK1
 DEFW STACK2
 7. Set the address of the stereo in the SP register
    for the first task:
      LD SP,STACK0
 8. Reset interrupts:
      DI
 LD A,#NN
 LD I,A
 LD HL,INT
 LD (#NNFF),HL
 IM 2
 EI
 9. Run the first program:
      JP PROG0
 Note:
  If a way out of the tasks is envisaged
RET, then place it at address STACK+24 each
the next stack address of the exit program. This is mo-
There may be a procedure for disabling one task
from the system (replacing the number of this replacement in TABL1
dacha to a different number), or exit procedure
yes from the system:
DI
 LD SP, standard value
 LD A,63
 LD I,A
 IM 1
 EI
 RET
 In the demo program there is one task -
cha draws a flashing square in the upper left
corner of the screenand polls the keyboard.Other
only draws a square in the upper right corner-
lu of the screen. When you press the space bar,
dit exit.
   If you want to use Mouzon, op-
upgrade the keyboard or increase some
-or counters, place CALLs in the indicated
oh place.
   Task restrictions:
1.Do not spoil memory occupied by other tasks
   chami.
2.Do not change register I.
3.Before using extended memory
   disable interrupts. Allow only
   when the standard one is installed
   configuration.
4.Do not prohibit interruptions for a long time.
   Restriction '3' can be removed if the system
topic to organize a configuration check,
storing it on the stack and then
recovery.

       ...ABOUT ELECTRONIC MAGAZINES.

   I, as an ordinary user, want
I would like to give a couple of comments for the production
tel of electronic magazines.
   1.If you come up with some cool
trick and put it in the magazine header, then
describe it in a journal, or assembler
text into the application so that others can too -
whether to use it.
   2.Expand the SAVE menu. For example, if in
there is a picture in the text, then add an item
SAVE SCREEN,if there is an assembly language
ting, then give the opportunity to unload it
immediately, not cutfrom the shipped stock
ty.
   3.Give the opportunity to ship Mouzons, with
with or without a player.
   That's all the criticism for now.

              ...ABOUT ADVERTISING.

   I will be happy to correspond with everyone
we who love and work with SPECCY.
   Do you have any questions about the program?
framing? Write. If I can, then answer
chu.
   Do you need a coder? If you liked
my developments (see above), write.
   And one more thing: who will help get the book P. Fe-
din "FULL DESCRIPTION AND FULL DISASSEMBLE -
LER TR-DOS 5.04(5.03)". It is also possible on disk.

                ...ABOUT YOURSELF.

   I'm 16 years old. I'm interested in programming
on SPECTRUME, which I have had for 6 years.
Now I have SCORPION. Perfectly
I know BASIC and Pascal. Pretty good
I also work in assembler.

              ...ABOUT FAREWELL.

   Well, my epic has come to an end, over
where I worked for a month and a half.
   Wishes, comments, suggestions and requests -
then send letters to:

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