KrNews #10 20 августа 1999

Программирование

CODING - Intro to 256 bytes?

_


               CODING ...
_


(C) Viper / TEchno Lab'99


            Intro to 256 bytes?


  In connection with the nomination 512 intro to CC999
some question arose, whether
write your intro in 256 bytes? The answer is simple -
not only possible, but this figure
easily blocked. An example is a Screen Saver for KrNews, which
you could watch for a few
numbers in a row. The reason for such constancy - a small 
amount of memory required for his work. It takes only 153 bytes!

And if you remove the poll keypad (standard Screen Saver;), 
then 145 bytes, brings it to the limit is 128 bytes. AND

this despite the fact that he actively uses
stack for its work. This Screen Saver - Full Screen (fullscreen)
Program is not required 128'oy memory.
Need only address table memory screen, located to the smooth
address, in this version # C000. Naturally, all realtime and 
nothing is cut. 

  All this SS was written as a 96,
if not before, so do not blame me.



  If someone does not know:

REPT 16
PUSH HL
ENDR


  - Directive Zx Asm3.10, correspond

DUP 1916
PUSH HL; in Alasm'e
EDUP

.16 PUSH HL; - in Storm'e

 -I mean PUSH repeat 16 times in a row


  So:


BEG EQU 7; min-distance
ENX EQU 63; max-lines
GTAB EQU # C000; address table

ORG # 8000


FLIC LD DE, # 401F; construction
LD HL, GTAB; table
LD B, H
FLI INC DE
LD (HL), E
INC L
LD (HL), D
INC HL
DEC DE

INC D; standard Down
LD A, D
AND 7
JR NZ, FL1
LD A, E
SUB # E0
LD E, A
JR NC, FL1
LD A, D
SUB 8
LD D, A

FL1 DJNZ FLI

EI
LD DE, GTAB
EXX
LD E, 96; half of the screen

SFX LD B, BEG
CYCLE1 LD HL, # FFFF; terrible number
CALL CYC2
HALT
INC HL; inversion though:)
CALL CYC2
INC B
LD A, B
CP ENX
JR C, CYCLE1

CYCLE2 DEC HL; back to the Universe
CALL CYC2
HALT
INC HL
CALL CYC2
DEC B
LD A, B
CP BEG
JR NC, CYCLE2
JR SFX

CYC2 LD (OLDSP +1), SP
LD A, B
SRL A
CYC21 LD C, A
ADD A, E; added 96 for

                  ; Middle of the screen

EXX
LD H, E; in the E -0
LD L, A
ADD HL, HL; multiplication by 2

ADD HL, DE; address, in which at
                  ; Hoditsya display ad
                  , Res (well said)
LD SP, HL; in his stekpoynt
POP HL; display address
LD SP, HL; again stekpoynt

EXX
REPT 16
PUSH HL; long line
ENDR

SUB C; or LD A, E-no
SUB C; SUB C difference

EXX
LD H, E; symmetry is still
LD L, A
ADD HL, HL
ADD HL, DE
LD SP, HL
POP HL
LD SP, HL
EXX

REPT 16
PUSH HL
ENDR

LD A, C
ADD A, B
CP E; off the screen
JP C, CYC21; no climbs?

OLDSP LD SP, 0, and that the stack?
SUB A
IN A, (# FE); do not touch
CPL; keys!
AND # 1F
RET Z
POP HL
RET

_