Programs - Screen cleaning program.

    Screen Cleaner

    Here is a cleaning program
screen written in language
ASSEMBLY.  This program can be
use as for
use in your
programs and for training
in practical programming
in ASSEMBLY.
    
    Briefly describe the work
programs can be done like this:
    
    1. Every byte is first
Six kilobytes of screen
area (display file without
attributes) undergoes a shift
to the left, with the most significant bit
bytes are written to the flag
carry 'C' and then get lost.
The effect that occurs when
running this program I
I probably won’t describe it, because...
You can follow it yourself
monitor after launch
programs.
    
    2. Second part of the program
performs attribute cleanup with
screen.   The screen will be filled
CURRENT ATTRIBUTES
contained in the system
variable 'ATTR_P'.
    
    10 ENT $ ;determine the address
run with 'R' command  
    20 DI; maskable prohibition
interrupt
    30 LD B,8 ;cycle counter-8
byte shifts
  40 MOVE
    50 LD HL,16384;in HL -
the beginning of the screen area.  60 LD
DE,6144 ;its length without attributes
  70 ADD        
    80 RL (HL) ;shift left
byte address of kth in 'HL'
    90 INC HL ;'HL'- increase
per unit
    100 DEC DE ;Decreasing 'DE'
per unit
    110 LDA,D ;Check
counter in 'DE'
    120 OR E ;to zero
    130 JR NZ,ADD ;if not zero
it's not the end
    140 DJNZ MOVE ;full screen
shifted by 1, and so on 8 times
    ;the second begins here
part of the program 
    150 LD HL,22528 ;beginning
attribute areas
    160 LD DE,22529;plus one
byte
    170 LD BC,768 ;area length
attributes
    180 LD A,(23693);download
current value
    190 LD (HL),A ;to the first byte
attributes
    200 LDIR; and the rest
    210 EI ;resolution
interrupts
    220 RET ;return