Programmers - IMMORTAL # 2 (immortality in the games).

<b>Programmers</b> - IMMORTAL # 2 (immortality in the games).

          IMMORTAL # 2

(C) Rzhavelschik.
________________________________


      Instead of preface.


   To continue this column originally was not in my plans
but recently I stumbled upon
interesting phrase in the ON-LINE, and
namely: "... read the above and realized that hardly when
I can explain something that is not
hacker ... "(for the accuracy of quotations
I can not vouch, but the meaning of this).
After that, I reread your
Op ... Hmmm, some of the gaps
available.


   To start finish. In the first
Part I forgot to mention one
a little nastiness, which is
the name "binary - decimal
representation of numbers. "What lies behind this catchy term? 
Here's what: sometimes, for convenience of calculation, or for 
certain number of other purposes set out in

special type with the command
DAA (# 27). In this representation nibbles contain the code 
decimal digits 0 to 9. So way in bytes can be placed

numbers up to # 99. Chasto program
constructed so that it works with
"Kvazidesyatichnoy" counting system. This means that the 
contents register should be considered as a decimal, ie, # 35 # 
35 = 99 = 99 and etc. In short, if in the beginning of the game

given time, 60 seconds, then the search should not # 3e # 3c # 
32 (LD a, 60 ...), and # 3e # 60 # 32 is LD

a, # 60!. Very popular this
distorted in the programs with the clock (in
basically - in the race). Example:
Wec le Mons at the start of the counter
shows a 66.0. Search LD A, 66
No results found. Applying the concept of binary - decimal
representation (BCD) are looking for LD
A, # 66 ... Bummer - there is no such letter
in this word. It follows
pad, which exhibited a second
with tenths through
register-pair.

   It should be noted that since
standard command processing
dvubaytnyh numbers here do not apply to standard intel'ovsky
location of the "long" numbers in
Memory is often sacrificed and bytes
can stand there in a staggered
order. Found in the final
result, the procedure set the time looked like this:

 LD HL, # 1066
 LD (addr), HL


   Well, perhaps this can be
complete an introductory course anatomy
programs for novice hackers.
Finally I can only say that the most complex structure is 
usually have tekstovushki (if they

codes) and a wide adventyury and most indigestible -
compiled with BASIC.

       ________________


   And now, in fact, that for which I have started a 
continuation This articles.


   I believe that many, inspired by the prospect of an easy 
life, famously broke all my (and others') game, and went into 
the taste and, broken in the dust all of which failed to reach, 
rested in debugerom a rhetorical question: Where

will be put? But on this occasion
"... I have a library of". "
Perhaps you have already tried a way to select INFINIT'a with
ADM'a (not so easy, eh?)
by shadow businesses scorpoin'a
(Khm. .. convenient course, but all
same as that ...) or have made the
large selection of games genre "right now
I'll show you all. "


   A further issue is dedicated to - where we put. However,
I must say that I like is not going to rewrite the booklet
"Caches ZX", and do not intend to
write a book "How to make
intro. "Intra I do not dabble in (almost). I hope not
insult you in the best feelings,
If we show how to make a choice
immortality of BASIC. For sure
Have you ever seen a tape versions of this version: loader stop 
pressing BREAK; from the row containing the REM and

POKE's, REM and the loader is removed
starts again. In disk
Version LOAD'er not very tormoznesh, because of this you can 
insert the following lines: 

 30 PRINT "inf.lives? (Y / N)"
 40 LET K $ = inkey $: IF K $ = "y" OR

     K $ - "Y" THEN POKE addr, n:

     GOTO 60
 50 GOTO 40


   Remember? Well. Never
so do not do - it's ungrammatical
and cumbersome. More correct to ask this insidious problem of 
the codes and read the answer from the codes the same. This is 
especially true for the 128-x toys, code loader, in

you want to change the contents of multiple memory pages. Here 
is a sample code menus for this case:


LD BC, # 000E - L5D83
LD DE, L5D9B)
XOR A) printing
CALL # 203C)
LD BC, # 0010) Menu
LD A, # 00)
LD DE, L5DAA)
CALL # 203C -
JR L5DBB
DEFB # 80
DEFB # 16, # 0A, # 0A L5D9B
DEFM "1.INF.LIVES"
DEFB # FF
DEFB # 16, # 0C, # 0A L5DAA
DEFM "2.NORMAL GAME"
DEFB # FF
LD BC, # F7FE - L5DBB
IN A, (C))
BIT 0, A) Survey
JR Z, L5DC9)
BIT 1, A) keys
RET Z)
JR L5DBB -
LD BC, # 7FFD L5DC9
LD A, # 14
DI
OUT (C), A
XOR A
LD (# C7CA), A
LD A, # 16
DI
LD BC, # 7FFD
OUT (C), A
XOR A
LD (# C472), A
RET
LD A, # 02
CALL # 1601
JR L5D83


   Comment: procedure # 203C
prints a message to
at DE, a length of BC's current
stream, which is installed
procedure # 1601 (A contains the thread number). The main 
screen - stream 2, the service - 1. Please

attention to the procedure for L5DC9,
this is the "obessmerchivanie.
This fragment is called
CALL'om after downloading the program, and RET is launching
games (incidentally, this fragment is taken
from my version ARMYMOVE1 '& amp2 in one bottle).
# As you can see, nothing complicated in the
so no menus, and in Basic
it is not implemented, since there
Switched pages of RAM. Naturally, there may
Other variants of this procedure, especially
part of the print menu. I can imagine how rasfyrkalis counting
After reading to themselves as professionals
CALL # 203C. Typically, for purposes thereof,
use something like this:

LD HL, addr
LD A, (HL) <-LOOP
OR A
RET Z
RST # 10
INC HL
JR LOOP


   Both options are understood and control codes used BASIC 
variables. If you the worst possible moment dumped

a terrible attack of laziness, we can
try to build the BASIC and
codes to simplify the print job and poll keys. Present to your 
attention now masterpiece lazy:


 0 REM (code loader)
15 PRINT AT PI * PI, PI * PI; "INF.

    LIVES (Y / N) ": PAUSE NOT PI:

    IF INKEY $ = "y" THEN POKE VAL

    "23908", VAL "182"
20 BORDER NOT PI: CLEAR VAL "2449

    9 ": RANDOMIZE USR VAL" 23872 "


   In the codes of 23,907 stood # 3e
# 35, and after - LD (addr), A. You
Of course, remember that # 35 <-> DEC
(HL), and 182 <-> OR (HL). If you answer "Y" DEC has changed in 
the OR, and after downloading the codes were put in toys. By 
the way, with all the splendor of BASIC, this phenomenon 
represents monoloader. 

   According to the principle of its action
this programm directly adjacent to such beloved by many
hackers INTRO. Usually INTRO
loaded and work out before loading the main program by changing 
a few bytes in the loader. Since it has a solid volume 
(scrolling text, music, etc.) then you have had a good 
opportunity to make fun of the user, hinting that if he will 
guess the riddle and click on klaviatute response (the word of 
the 11 letters), then maybe get immortality.

For completeness, we consider the course
primerchik:

LD BC, # 7FFE - LOOP
IN A, (C)) poll
BIT 0, A) space
JR NZ, L61ED -
DI
IM 1
CALL # 6B2E
LD HL, # 4000
LD DE, # 4001
LD BC, # 1AFF
LDIR
RET
NOP L61ED
LD A, # FD
IN A, (# FE)
BIT 4, A -> "G"
JR NZ, L621E
LD A, # BF
IN A, (# FE)
BIT 1, A -> "L"
JR NZ, L621E
LD A, # FB
IN A, (# FE)
BIT 2, A -> "E"
JR NZ, L621E
LD A, # 7F
IN A, (# FE)
BIT 3, A -> "N"
JR NZ, L621E
LD A, # 22
LD (# 5D73), A
LD B, # 27
OR # F8 L6217
OUT (# FE), A
INC A
DJNZ L6217
JR LOOP L621E


   That thing works like this: if
pressed "space", then continues
Loading - if not, is a poll
keyboard. When pressed the first
key password, the program checks whether the next is pressed. If
not pressed the first letter, then exits the program at the 
polling loop. When pressed all the letters of the password, the 
boot loader changed bytes and intra having fun

blinked border, enters the loop. In the running line,
closer to an end, says that
if the user knows the name of the vocalist DEICIDE, it can
it immediately to confirm and get over its cultural level of 
eternal life. 

   One subtlety: nothing, producing clearly visible effect
consistent with such applets can not be put as
each correct keystroke
increases the run time
cycle, leading to a slowdown in the series
standing loop operations (for example, will jump animation). 
This will reveal the code brute force. Marquee

and music in this example are in
cycle interruption.

   At a certain skill such protsedurku can cram
and the game itself, although perhaps it
have a bad taste (the more so
in many games and so have corporate CHEAT MODE).

   Well, now, seems to really end. I hope that
Read'll send you the benefit of
and you're not going to die from
boredom.