ZX Review #5-6 04 ноября 1997

PC     Программирование

Authoring - Trampoline (S. Veremeenko).

     Authoring



(C) S. Veremeenko


           DIVING BOARDS


   The software package Springboard
designed to programmistovlyubiteley who have mastered 
programming in assembler or Z80 I8080. It allows you to 
immediately only on the basis of the knowledge that acquired 
programming practice for Spectrum (Orion, Vector, Specialist, 
etc.). write a quite a full program for the IBM PC.


   Hobbyists, even in
to master programming for 8-bit machines
faces significant
difficulties in the transition to a more promising and a 
perfect platform for PC. It These difficulties have caused many

spektrumistov to mistrust
PC, the illusion of incredible complexity and even the 
cleverness of this, in general, a good car. Main difficulties 
faced by "virtuoso balalaika 8-bit" when trying to develop PC: 

   1. The complex structure of the segmentation and 
memory-related these problems of distribution and

memory management. Has no
analogue in any of the 8-bit computers.

   2. The need for sufficient
complete study of DOS "inside"
at the level of interrupt vectors UP
How you write your first program, since even the most
Simple programm of the 10-15 teams are already required to 
interact with DOS. 

   3. Unusual and complex syntax assembler processor I86
(So ​​I'll continue to call all the family PC-shnyh processors).

   4. New to spektrumista
command system. It is the smallest problem, and it could be and 
not to mention, since I86 and Z80 fairly close relatives, and 
for most teams Z80 have complete analogues in the system

I86 (but not vice versa!)

   Tramlin can stretch
time solution to all these
problems. Its first program
on the springboard you can write,
even using mnemonics Z80,
Although this stage is better to step immediately. Use of the 
rich and extremely useful system commands I86 only those that 
have counterparts in the set Z80 - anyway, what to eat soup 
with tweezers, ignoring lying near spoon.



    Characteristic features

           Jumping


   A program written to assemble a springboard for
its structure is not very different from a program written
for the Spectrum. It should start heading type:

include "keyboard.lib"
include "standard.fnt"
include "disk.lib"
include "s320_200.lib"


   PROGRAMM Z80


   And then write how would write on GENS-4. Header means that 
you plan to use the keyboard will refer to the floppy drive, 
hard drive or RAM disk, something you want to display

in video mode 13h and meet the standard fonts.

   The argument of PROGRAMM
According to Springboard, that you have
have not mastered the command system I86, and
he may run into a mnemonic Z80. In this mode, Springboard
will pick up for teams Z80
the most suitable replacement of the
arsenal of I86, although the use of teams is welcome and I86
in this mode. You can randomly shuffle the team of
both sets, Springboard will understand.

   When the use of mnemonics
Z80 is for you to be passed
stage, the argument in the function of Z80
PROGRAMM can omit, but the function itself can not be disposed 
of. Among other things, it allocates memory, sets up equipment 
machines, prepares information for subsequent correct exit from 
your program, in short - makes all the grunt work that

should make the programmer PC,
but to which the unused spektrumisty.

   If the combined entity of
different sets of commands could
without too much difficulty, then combine the two syntaxes, you 
know, is impossible. Since Trampoline use involves a gradual 
transition from programming style

Spectrum programming PC,
preference was given to the assembler syntax I86. Most
major differences occur at
selection stage model of memory and
initialization, and it all makes trampoline itself, without your
participation, so remember to quite a bit.


   1. Where in assembler Z80
You put parentheses to
indicate indirect addressing,
Requires a square trampoline.

Example: gens-4 LD A, (HL)

        Springboard LD A, [HL] or MOV AL, [BX]


   2. Labels and variable names -
different objects.


   The label can be placed only
an executable command, and must
end with a colon and the name
variable might indicate
only data and not a colon
ends.

Example: gens-4 Springboard


          CALL PROC1 CALL PROC1

          ........... ............

  PROC1 LD HL, (DATA) PROC1: LD HL, [DATA]

          RET RET

  DATA DW # 4000 DATA DW 4000h

Note the difference in
designation HEX-numbers.


   3. Labels and variable names
are not constant and can not be directly used in expressions. 
For translation label or variable name in

constant is the operator offset.

Example: gens-4 Springboard

          LD HL, NAME LD HL, offset NAME

  NAME LD DE, DATA NAME: LD DE, offset DATA

          .............. ......................

  DATA DW 15000 15000 DATA DW


   4. Since I86 is
16-bit (minimum) processor, sometimes there is uncertainty when 
the context of the program can not determine the size of the 
operand. In such cases have to refine it.


Example: wrong

          INC [HL]; that increment, byte or word?


          correctly

          INC [BYTE HL]; increment byte at the address in HL

          INC [WORD HL]; increment word address of the HL


   Such situations occur infrequently and are tracked by 
assembler, so if you are asked to clarify the type of the 
operand, do not be surprised very much. 

   That is, in fact, all the differences in syntax that you
need to remember to start
work in the jump. There are
other, but with them you will encounter
Even then, when the trampoline will
you passed stage.

   From the perspective of a programmer
operating in a trampoline in his
disposal of computer RAM
65536 bytes, a simple disk interface and coordinate
display medium resolution
operating mode of the available 255 colors from a palette of
262144 colors. Stack imposed for
outside your accessible address
space and automatically
initialized at startup
program. Screen break
implemented as a
Spectrum, but I register and set interrupt vector in
memory is not necessary. Enough to anywhere in the program
place interrupt handling routine with a reserved name 
INTERRUPT, and the team will switch IM2 interruption. Stored in 
the stack registers interrupt routine is also not

needed. Trampoline about such trifles
takes care of itself. Interrupt routine must be terminated by a 
team of RETF. 

   There is another reserved label BEGIN. It should be
awarded the team with which your program will start.
The command HALT, as usual, makes a pause before the 
interruption, regardless of what trap mode (IM 0 and IM 2)

installed. Disable interruptions can not. When you try to ban
interrupt you paralizuete MSDOS,
And it will not be tolerated. Correct exit to DOS by
team-EXIT.


      Library Functions


   Accessing external devices to the PC more often performed by 
software interrupts. BIOS and DOS provide for this great 
opportunity, and you can use them almost without restriction, 
but for beginners it is quite difficult.

Therefore, in the "Springboard" introduced a much simpler and 
more convenient commands to access external devices sold by the 
drivers, plug-teams include in the header. Despite

significant amount of these drivers do not take away from you no
bytes of the available address space of your program
(65536 bytes). All of them are located in another memory 
segment, as and stack. Consider some additional commands that

You can use by connecting the appropriate driver.


   Keyboard (keyboard.lib)


  keyboard.lib complements
teams with two teams:


   KEYBOARD 

   KEY 


  KEYBOARD command sets
mode of the keyboard.

KEYBOARD 0 - waiting press

             keys.
KEYBOARD 1 - read the key code

             without waiting.
KEYBOARD 2 - joystick mode.


   Team-KEY at work in
zero mode, the program stops and waits for a keypress. If you 
press in the battery transferred to ASCII.


   In the first mode command KEY
do not stop the program, and
immediately produces ASCII thrown down with the flag of Z, if 
any key is pressed, or 0FFh to set Z, if at this moment

do not press any key. Similarly, the function INKEY BASIC.

   In the second mode command KEY
has an argument that can
take values ​​from 0 to 13.
The argument indicates the group analyzed the keys. For 
example, in the zero group includes key Left-arrow, right 
arrow, up arrow, the arrow down "," Left CTRL "," Left

SHIFT "," left ALT "and" SPACE ".
As you can see, this is similar discharges Kempston-way 
controller, and the team KEY 0 in the second mode completely 
analogous to the team read joystick port

Spectrum. Keystroke sets 1 in the corresponding
a low battery. Simultaneously may be pressed a few buttons.

Bit 7 6 5 4 3 2 1 0

0 Space Alt l. Shift l. Ctrl l. Down Up Right Left
1 Enter Back Pg. DW. End Delete Pg.Up Home INSERT

2 7 6 5 4 3 2 1 ~
3 Alt r. Ctrl r. Shift r. + - 0 8 September

4 UYTREWQ Tab
May nothing Pr.Scr. \] [P O I

6 JHGFDSA Caps Sh.
7 nothing nothing nothing nothing ": LK

8 <MNBVCXZ
9 nothing nothing nothing nothing nothing nothing? >

klav.tsifr.
10 5 4 9 8 7 * / Num lock
11 + -. 0 3 2 1 6

12 F7 F6 F5 F4 F3 F2 F1 Esc
13 Pause EnterDig ScrLock F12 F11 F10 F9 F8


     Screen (s320_200.lib and

         s256_240.lib)


   In principle, you can set any video mode and work with him. 
Driver s320_256.lib establishes a standard video mode 13h, with 
the resolution 320 * 200 pixels with 256 colors,

used in most video games PC. Driver s256_240.lib
establishes a non-standard, but
convenient to work with 8-bit
data mode 256 * 240 with 256 colors. This mode has square 
pixels, ie circle looks like a circle, but not

elongated horizontal ellipse
and simple determination.
Taken together, this can improve performance of the program
2-3 times due to the exclusion
necessary geometric
correction and calculation of coordinates
pixels. This is important because
spektrumisty for the most part people are not rich, and really 
have to bear in mind the 386SX-33, which is already cheaper 
SCORPION or profit, if not purchase expensive SVGA-monitor and 
limit TV-card and work with a TV or reworked CGA-Monitor. 


   Drivers and s320_200.lib
s256_240.lib give the programmer a great opportunity.

   Consider a system of graphic commands.


   BORDER R, G, B


   This command sets
color of the frame around the screen and has a
three parameters, each of which opreredelyaet intensity
the corresponding primary color. Parameters can take
values ​​from 0 to 5, all of which gives 216 colors.


   COLOR R, G, B


   Transmits to the battery code
appropriate to order flowers. Meaning of the parameters are the 
same. In addition, there is another form of

This command has one parameter.
We will consider it when we get
to the "user palette.


   PLOT


   Without parameter sets
on-screen pixel color is determined by the contents of the 
battery. In the driver s256 * 240.lib coordinate X is defined 
by register L, coordinate Y - register H. In

driver s320_200.lib calculation of coordinates is more 
complicated. Contents of register HL (BX) is determined 
according to the formula HL = X +320 * Y, where X and Y - 
coordinates of the pixel. In the calculation of the coordinates 
is difficult to do without the relatively slow teams of 
multiplication and division, and this mode, the speed drops, 
although spektrumistu accustomed to the snail's pace of its 
favorite car, even in this case, the performance seems 
fantastic. 

   If the battery code 0FFh,
pixel color is not changed. This
allows you to display sprites on
background without distortion. Those pixels of the sprite, 
through which must translucent background, must be set to 0FFh.



   PLOT T


   Similarly, PLOT, but the color of the
battery is added to the pixel color. Command displays 
translucent objects - ghosts, bottles with drinks and stuff. 


   PLOT?


   Reading in the battery package
color from the specified HL pixel.


   AT X, Y


   Sets the position to derive the symbol commands PRINT and
PRINT T. X and Y can be given directly, the variables
in memory or the contents of any
registers from the group HL, BC, DE
(BX, CX, DX). Drivers
s320_200.lib options for 16-bit, because X coordinate in one
bytes does not fit, and for
s256_240.lib - 8 bit. For example, we give the AT command
B, H. In this case, the contents of register B to determine the 
coordinates X, and H - Y.



   INK R, G, B


   Color for subsequent withdrawal
characters.


   PRINT


   Displays a symbol in the position of AT.
ASCII character in the accumulator,
font and character size are defined by the activated fonts. 
Following the withdrawal of the next character position is 
shifted to the right by an amount determined by the width of 
the symbol, which is installed when activated font. The 
background of the symbols and between symbols is preserved 
(command PAPER no).



   PRINT T


   Conclusion translucent characters. The rest is similar to 
PRINT. 


   FONT <name>


   Activation of the font. After this
team font and size of the characters defined by this font.
Whole teams include You can enter multiple fonts,
the only restriction - the total of the amount should not 
exceed 30 - 40 kB. Font 8 * 8 pixels takes 2 kB, and 9 * 16 - 
about 5kB. 


   PALET <label>, <number

   programmable color>


   An extremely powerful team
provides a simple means
achieve amazing results. All commands have arguments <R>, <G>, 
, except BORDER, have another form. If you

give an argument from 0 to 38,
the color of the pixel will be
determined by the "user palette, which includes only 39
colors, but they can be reused
redefined in the course of the program.

   To use the palette of the user, must be somewhere
create a structure like this:

TABCOLOR DB n, R0, G0, B0

           DB m, R1, G1, B1

           ..................

           DB z, Ri, Gi, Bi

where n, m ,.... z - the number of your
color, which appears in teams INK, COLOR, and others, as
Ri, Gi, Bi - the intensity of the color components of color.
They can range from
0 to 63. It is easy to calculate that
a palette of user you are
get access to 262,144 colors.

   To enable the user palette, enough to give the command PALET 
TABCOLOR, 5 if you want, for example, set 5 colors in your 
palette. Huge number of colors - not

The main advantage of the team PALET. Imagine the picture: 
night city, against the facade of night club is a police car, 
leaning on the hood of a police officer and smokes. Twinkling 
stars that periodically change the color of neon advertising 
establishments in the windows are visible reflections color 
music, hanging flasher machines, from time to time flashes a 
light cigarette. And while does not redraw the screen or

one bit! Just in the process
interrupt operates a small
podprogrammka using
Team PALET. How - you already seem to understand.


   Work with disks (disk.lib)


   MSDOS provides a very
great opportunity to work with
disk drives. However,
use functions MSDOS requires some training.
A complete study of the disk service
MSDOS can take a long time. Therefore, at first, better to use 
a much simpler and more understandable to driver commands 
disk.lib. 

   Commands are simplified to the extent possible. Of course, 
disk.lib does not use 10% of capacity

MSDOS, but for those who only yesterday
spitting, trying to squeeze something
from TR-DOS, its ability to impress.

   At first, enumerate limitations disk.lib compared with 
MSDOS. All work is performed in a single directory, and 
precisely in the fact of which was running your program. If

program was started from a floppy disk, hard disk in the 
directory C: \ GAMES \ DIZZY or electronic

disk, the read and write
it will only get there. This is quite a natural restriction for
game programs, electronic
magazines and so beloved hobbyists "DEMO".
At the same time allowed to work
with only one file. This is typical for TR-DOS, so that
spektrumisty special inconveniences are not
feel.

   Maximum file size is limited to 16 MB. On a floppy disk so
file, of course, will not be included because
that this restriction is not so
scary.

   Not supported by work with
file attributes. You can only use regular files.

   Now consider the commands
disk.lib.


   FILE <file name>


   This team, we indicate with
which file are going to work. If the filename is omitted, then
as the name used
string pointed to by register pair DE (DX).


   DELETE <file name>


   Deletes the specified file. Condition defaults the same.


   CREATE <file name>


   Creates a new file of zero
length with the specified name. Condition defaults the same.


   LOAD A, B, C, D


   Reading from the file specified
the last team FILE.

   Parameters:

   A - the address where will be reading. May be a sign, a 
variable name or the most variable. Absolute assignment

addresses may not have
sense. Why? Few think and understand.

   B - number of read
bytes. Can be defined absolutely, as a difference of marks or
the contents of the variable. Maximum - 65535.

   C and D. Determine the displacement
start reading from the beginning of the file. If omitted, the 
file read from the beginning. The entire file

is composed of a number of pages to 256
bytes, the same sectors in
TR-DOS. C - the page number (the word, the range 0-65535), D - 
displacement within the page (byte, range 0-255). These 
parameters can be set directly or as variable names.


   If your set shift
exceeds the real
file will install the flag C
and give the battery code
errors. So do all the teams with too disk.lib familiarity.


   SAVE A, B, C, D


   Writing to a file. Meaning of the parameters are the same. 
If you write in the file, there exist data

replaced writeable. If
length of an existing file does not
allows you to record the demanded number of bytes, or if you
set the offset close to his
end or even at the end of the length
file will automatically increase
until required. So you can safely write 60 kB to the newly 
created file with zero length. 


       Jobs at Springboard


   To begin a trampoline, you must first run it. He has a name 
tramplin. com. Once launched, you will see on

screen menu with the following items:

1. Editor
2. Assembler, without listing
3. Assembler with listing
4. Trial run
5. Conditions of registration


   Exit to DOS is carried out on
ESC.

   If you press 1, y
You will be asked to enter a filename, with
you are going to work.
The name of the file is stored on the fly
work session, and all programs
package will use it,
until you enter a new one. After
enter the name you enter the editor where you can get started 
with new file or continue with the

existing ones. After exiting the
editor, you can try
proassemblirovat program
selecting 2 or 3. If you
working with the hard disk - no problems, but if there is no 
hard drive, Think twice before choosing

assemble with the listing.
Listing a large program can
have a size of 1.5-2 MB, and check on the possibility of placing
file is not performed, because advance this size is not known.
Could be trouble ...


   If you have not admitted error
can then assemble
give a trial run and see
what do you navayal. If your
program does not "hang" the computer, and you have not 
forgotten about the need dependence to complete any of your

program command EXIT (required!), then exit
are returned to the trampoline and
will continue.


      Near-term prospects


   Currently we are working
to create a new library
Modules: drivers, mouse, printer, sound, built-in RAM disk. 
Will write a new Display Driver with Buffered screen, which 
uses the method "Dirty squares.



   Appendix: examples of the use of library functions.


          KEYBOARD 0

          ...............

          KEY

          CMP AL, 27

          JZ KEY_ESC; pressed Esc

          ...............
KEY_ESC: EXIT


          KEYBOARD 2

          ...............

          KEY 0

          CMP AL, 00010110b

          JZ UP_RIGHT_FIRE; if both are pressed

                                  , Up, Right, Ctrl-left


          COLOR 0,5,0

          MOV BL, 128; X-coordinate

          MOV BH, 120; Y-coordinate

          PLOT; yarkozelenaya point

                                  ; In the middle of the screen

          INC BL

          PLOT? ; AL = color code the next

                                  ; Horizontal


          BORDER 1,2,3; curb olive

          FONT MICRO; set the font

                                  , (If you have one)

                                  ;

          INK 0,1,3; we print color

                                  ; Navy

          AT 30,52; the upper left corner of the symbol

                                  ; Will coord. X = 30, Y = 52

          PRINT T; print transparent font


          PALET NIGHT, 5; lips. May a palette registers

                                  , "Night"

          ...............


          NIGHT DB 0,0,10,22; 0 Reg. blue star

                  DB 1,10,0,0; a reg. smoldering cigarette

                                    , In the teeth of a bully

                  DB 5,0,20,0; 5 reg. cat eyes

                  DB 11,17,17,17; 11 Reg. gray cat

                  DB 4,0,47,0; 4 Reg. green light

          NIGHT1 DB 0

          WPAL DW offset PFL3


          CREATE 'NIGHT.PAL'; create a file

          SAVE NIGHT, NIGHT1-NIGHT; record there palette

          LOAD [WPAL], 4,0,7; read from the file
; A variable PFL3 4 bytes starting at 8 from the beginning of 
the file 


          MOV DX, offset F_NAME

          DELETE


          ; Remove a file whose name in the variable F_NAME

          .........................


          F_NAME DB "NIGHT.PAL", 0



    WARNING: the program itself
 DIVING BOARDS you'll find in the catalog
 ZX REVIEW.


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