Coding - This time I will talk about displaying 64 characters per line.

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║  Coding.              ║
╙─────────────────────────────── ───────────────────────────────╜
(C) EVP-SOFT

 Hello everyone. After a long break, the column "Ko-
ding."  This time I will talk about displaying 64 characters in
line.
   All assembly texts are in ALASM format. And if any
be it GENS does not digest commands like LD A, LX, DUP or
INCBIN, then don’t call me with questions like “what is this command
replace?', but you just need to set 512 kb and switch to ALASM.

 First, let's prepare the font.  To improve output speed
The font must be from the usual format (when 8 bytes of each character are
pressed one after another) convert to a “third of the screen”, i.e. to
between bytes of the same character there was offset #100. Then the address of the sign
will be calculated like this:
LD H,0
        LD L,character code
        LD BC,FONT
        ADD HL,BC
in HL the first byte is now, for the next one we simply do INC H
   And if you don’t convert the font, then the sign code is first
you need to multiply by eight - and this is an extra 33 clock cycles:
LD H,0
        LDL,character code
        LD BC,FONT
        ADD HL,HL
        ADD HL,HL
        ADD HL,HL
        ADD HL,BC
in HL is now the first byte, for the next we do INC HL, but if
the font is located at an address that is a multiple of 8, then you can INC L
   Well, the font is converted using the following procedure:
ORG #6400.0
        LD HL,#8000
        LD DE,#4000
        LD BC,256
M1 PUSH HL
        PUSH DE
        PUSH BC
        LD B,8
M2 LD A,(HL)
        LD(DE),A
        INC L
        INC D
        DJNZ M2
        POP B.C.
        POP DE
        POP HL
        DEC B.C.
        INC E
        DUP 8
        INC HL
        EDUP
        LD A,C
        OR B
        JR NZ,M1
        RET
        ORG #8000.0
        INCBIN "FontbH.C" ;loading a regular font
 We assemble, then call STS. There we make CALL #6400, for-
Then we save the resulting font with the command SAVE "64$0.C" #4000,#800.

   There are several printing options. Each character can be stored
in the most significant nibble, and then, if the output is odd, then shift
him with the help of RRCA. Or you can store a copy in the younger half
the eldest one, and before outputting, discard the unnecessary half by mass
ke. But the fastest way to withdraw- is to have two backgrounds in memory -
that one is in the high nibbles, and the low ones are empty, the second corresponds
quite the opposite.
   However, in the body of the program, for better packaging, it is necessary to store
only one font, and create the second before launch:
FNT_EXT LD HL,FONTO ;font address
LD DE,FONT1 ;copy address
LD BC,#800 ;counter
FNT1 LD A,(HL) ; take a byte
 RLCA ; shift the most significant nibble to the least significant one
RLCA ;
RLCA ;
RLCA ;
 LD (DE),A ; put the result
INC HL ;addresses of the following
INC DE ;byte
 DEC BC ;decrease the counter
LD A,C ;if in BC still
 OR B ;not zero then
JR NZ,FNT1 ;cycle repeat
 RET ;otherwise return
FONTO INCBIN "64$0.C" ;font available
FONT1 DEFS #800 ;and here there will be a second font.

 The fastest way to print is to print two characters at a time
la.  This method, of course, has a drawback - sometimes you need to
print just one character. But in most cases it is necessary to
start a whole line at once, and then it turns out much faster.

  This procedure gets the beginning of a line in HL, and prints it until
will not encounter the CR code (#0D), if the line is short, it finishes it off
spaces. When exiting to HL, the next address after CR. So:

PRINT EX DE,HL ; save the text address
 LD A,32 ; set the counter of empty characters
 LD (PRT_X),A ;

 Now let's calculate the coordinates on the screen. In COORD_Y we enter the vertical
calposition, and in COORD_X - horizontal. But in practice
usually the horizontal position is 0, and then the processing unit
COORD_X can be excluded. The least significant bit of COORD_X must be equal to
0, i.e. X-address only odd:

LD A,0
COORD_Y EQU $-1
        LD B,A
        AND #07
        RRCA
        RRCA
        RRCA
;        LD C,0
;COORD_X EQU $-1
;        SRL C
;        OR C
        LD L,A
        LD A,B
        AND #18
        OR#40
        LD H,A
        LD (PRT_WR),HL ;save the address of the familiarity place

 Take two characters for printing:

 EX DE,HL ; return text address to HL

PRTS LD A,(HL) ; take the sign
 INC HL ; this is for the future
CP #A
        JP Z,PRTS ; ignore the LF code
PRT1 CP #D
        JP Z,PRT18 ; found the code CR - end of line

 LD E,A ; save the first character in E

PRT7 LD A,(HL) ; take the second sign
INC HL
        CP#A
        JP Z,PRT7 ; ignore LF
CP #D
        JP NZ,PRTCH ; if it is not CR, then we start printing

PRT13 DEC HL ; and if CR, then we’ll leave it for the first cycle

 LD A,#20 ; well, for now let's print a space

PRTCH PUSH HL ; save the text address

 LD L,A ; and let's start calculating the addresses of characters in the font
LD H,0
        LD BC,FONT1
        ADD HL,BC ; calculate the second (i.e. right) character
 EX DE,HL  ; DE will be the address of the second character
 LD H,0  ; and the first one will appear in HL soon
LD BC,FONTO
        ADD HL,BC ; calculate the first (i.e. left) character

LD BC,0 ; in BC they substituted the print address in advance
PRT_WR EQU $-2 ; via PRT_WR label
 LD A,C  ; this is for the future, next address
 INC A  ; printing, because automatic line translation here
 LD (PRT_WR),A ; no, then we only need one byte

 DUP 8 ; let's make a layout
 LD A,(DE) ;take the second character
 OR (HL) ; place the first one on it
 LD (BC), A ; and we put all this on the screen
 INC H ; find the addresses of the following
 INC D ;byte of these characters
 INC B ;move to the next line of the screen
 EDUP ; end of layout
 ORG $-3 ; we will erase the 3rd last. commands last layouts
; because they are unnecessary in it.

PRT15 LD A,0  ; counter of empty acquaintances,
PRT_X EQU $-1  ; first 32 will be substituted here
 DEC A ;
 LD (PRT_X),A ;

 POP HL ; restore the text address
 JP PRTS ;and start outputting the next two characters

 And this procedure adds spaces at the end of the line, very useful
but if there was already something underneath. If this is not necessary, then just kill
paradise everything related to the counter of empty acquaintances and the label
PRT_X, and where near the PRT1 mark there is JP Z,PRT18 instead of this JP
set RET Z. Otherwise, we type further:

PRT18 LD A,(PRT_X) ;check availability
 AND A ;empty acquaintances
 RET Z ;if not, then return

 PUSH HL ;otherwisesave the text address

 LD E,A ;E will have a number of familiar places for cleaning
 XOR A
        LD HL,(PRT_WR) ;address on screen
 LD B,8 ; familiarity height of course 8 lines
PRT10 PUSH HL
        PUSH BC
        LD B,E
PRT9 LD (HL),A
        INC L
        DJNZ PRT9 ;cleaning cycle of one familiarity area 8x8(!)
 POP BC
        POP HL
        INC H
        DJNZ PRT10 ;cleaning cycle of the remaining acquaintances

 POP HL ; restore the text address
 RET ;and return

 Here is an example of the 'LINE' procedure, which outputs to
There are two stripes of "*" symbols at the top and bottom of the screen:

LINE XOR A
        LD(Y),A
;        LD (X),A  ;;;; see COODR_X
 LD HL,LIN1  ;
 CALL PRINT  ; LD A,23  ;
 LD (Y),A  ;
;        XOR A  ;;;;
;        LD (X),A  ;;;;
 LD HL,LIN1
        CALL PRINT
        RET
LIN1 DEFS 64,"*"
        DEFB #D



 Well, since we started the topic of outputting 64 characters, now I will bring
I'll give you an example under IS-DOS. Namely, the new driver 64 characters, in
Differences from the standard "tybCh.typ" this will print the entire tab-
face of 256 characters.

 Let's start with the theory. The driver, like the resident, must have at the end
the word #FFFF, after which there is a table of addresses that need to be
configure during installation (set.com does this). Otherwise, if in
the driver contains the commands JP nn, LD a,(nn), LD HL,nn then it is not allowed
will move in memory and the system will simply freeze. And hell-
res in the table is one less than the real ones, this is done to simplify
Setting up the commands JP nn, LD A, (nn) and similar ones.

 At the beginning of the driver there should be the following table:
 DEFW installation address, if 0 then it is not called
 DEFW address of the PP for displaying the symbol on the screen, input data:A - code
      symbol, DE' is the address on the screen, and left or right should be
      count for yourself. Output: if there was a right symbol, then E'+1
 DEFW address of the inversion control PP: A:Z - no, A:NZ - yes
 DEFW address of PP for setting coordinates, input: BC - logical position,
      output: DE' - address on screen, left or right character -
      remember in the driver.
 DEFB length of the cursor in pixels, in this case it is 4.
 DEFW physical coordinates
 DEFW log. coordinates
 DEFB type: 0-screen/1-printer
 DEFW error handling PCB address.


 So, let's start creating the driver.
;
; Driver 64 characters per line
; Under IS-DOS
; (C) EVP-SOFT at 1998.04.12
;

        ORG 50000

        DEFW 0 ; this standard table
M5 EQU $-1 ; see description above.
 DEFW TTYOYT ;
M6 EQU $-1 ;
 DEFW PRCPL ;
M7 EQU $-1 ;
 DEFW PRADD ;
 DEFB 4,0,0,0,0,0 ;
M13 EQU $-1 ;
 DEFW M12 ;


 To speed up printing, the font will be in “screen format” (see
previous article).  But you just need the most significant nibble
duplicate in junior, because in IS-DOS there is not enough memory to
have two separate fonts.

FONT INCBIN "64$0&1.C"

 Inversion control:

PRCPL OR A
        JR Z,M4
        LD A,#2F ;#2F is the CPL command code
M4 LD (M3),A
M12 XOR A ; and here, if necessary, we will transfer processing
 RET ;errors. Those. just ignore them

 And here we calculate the print coordinates.

PRADD SRL C
        SBC A,A ; define
 XOR #F0 ; left or right character
M9 LD (M1),A ; in familiarity 8x8
 LD A,B
        AND #07
        RRCA
        RRCA
        RRCAOR C
        LD E,A
        LD A,B
        AND #18
        OR#40
        LD D,A
        EXX ; now in DE' there will be an address on the screen
 RET ; and you can come back

 Now it’s time for the PP to be displayed on the screen:

TTYOYT EXX
        LD H,0
        LD L,A
M10 LD BC,FONT
        ADD HL,BC
        EX DE,HL
        LD BC,#0800 ; in B loop counter
M1 EQU $-2 ; in C "left or right" selection mask
M15 LD A,(DE) ;;
M3 NOP ; in case of inversion, enter #2F here, i.e. CPL
 AND C ;;
 XOR (HL) ;;
 AND C ;; Well, everything is as usual here.
 XOR (HL) ;;
 LD (HL),A ;;
 INC D ;;
 INC H ;;
DJNZ M15
        LD A,H ; restore the starting address
 SUB 8 ;
 LD D,A ; and return it to D, then it will be D'
 LD A,C ; change the mask from left to right or
 CPL ; on the contrary
M8 LD (M1),A ;
 RLA ; if from right to left, then
 LD A,0 ; need to move on to the next one
ADC A,L ; acquaintance
 LD E,A ; put the result in E
 EXX ;now DE will become DE', and the rest is unimportant
 RET

 Well, now the table of addresses where direct addressing was:

 DEFW #FFFF ; table sign
 DEFW M4,M5,M6,M7,M8,M9,M10,M13 ;addresses-1, or more simply
                                          ;speaking, command addresses

 The length of the file is of great importance if at the end of the table the address
extra bytes will appear, even zeros, then when installing this
something will go wrong with the driver.

 ... this driver can be downloaded on HARD BBS ...