Studies - Cleanup of the specified window screen.

<b>Studies</b> - Cleanup of the specified window screen.

(C) Kobyakov M., Nakhodka


   Offered in the section "Studies"
its program to clean the windows of the specified screen. 
Coordinates X, Y, as well as the width and height are specified 
in pixels. The only restriction - the X coordinate should 
always be> = 8! To clear the entire screen to set the width = 0 
height = 176.


   But now offer readers
improve my program
in particular, to reduce the length and
improve performance. Who
do better?

   A bit of criticism in your address.
Where are the hexadecimal
dumps programs in "Etudes"? Of course, I understand - 
space-saving, expensive paper and etc., but that is not for 
everyone Like typing program

assembler, and the lesson is quite time consuming. And typing
hex dump of keystrokes decreases (as you calculated)
5-6 times! What time-saving and nerve end-user! However, in the 
letter, I do not dump cite, as if you write by hand a bunch of 
numbers, you can ponadelat no less a bunch of errors. 

   Is it possible to return an indication of
length and start address after
subroutines, or at least the length of
(As in ZX REVIEW N1-2 for this
year).

   Finally a small request: Is it possible to increase
magazine well, at least on 5-6 pages?
140.
; Window clearer
; By Lazy Max


        LD D, 0
; X-coord. upper left corner

        LD E, 175
; Y-coord. upper left corner

        LD A, 175

        SUB E

        LD E, A

        AND A

        RRA

        SCF

        RRA

        AND A

        RRA

        XOR E

        AND 248

        XOR E

        LD H, A

        LD A, D

        RLCA

        RLCA

        RLCA

        XOR E

        AND 199

        XOR E

        RLCA

        RLCA

        LD L, A

        LD A, D

        AND 7

        LD E, A

        LD A, 8

        SUB E

        LD E, A

        LD B, A

        LD A, 255
GO1 AND A

        RLA

        DJNZ GO1

        LD D, A

        PUSH HL

        LD HL, BUFF

        LD C, (HL)

        INC HL

        LD B, (HL)

        POP HL
REP PUSH HL

        PUSH BC

        LD A, D

        AND (HL)

        LD (HL), A

        PUSH DE

        PUSH BC

        LD A, B

        SUB E

        CP 8

        JR C, CNT

        AND 248

        RRA

        RRA

        RRA

        LD B, A

        SUB A
L1 INC HL

        LD (HL), A

        DJNZ L1
CNT POP BC

        LD A, B

        SUB E

        AND 248

        ADD A, E

        LD D, A

        LD A, B

        SUB D

        JR Z, PASS

        LD B, A

        LD A, 255
L2 AND A

        RRA

        DJNZ L2

        INC HL

        AND (HL)

        LD (HL), A
PASS POP DE

        POP BC

        POP HL

        CALL DLINE

        DEC C

        LD A, C

        AND A

        JR NZ, REP

        RET
DLINE INC H

        LD A, H

        AND 7

        RET NZ

        LD A, L

        ADD A, 32

        LD L, A

        RET C

        LD A, H

        SUB 8

        LD H, A

        RET

BUFF DEFB 30,53
, Height, width


   Code length: 128.
2

   Ed.: Some thoughts on the criticism. In our opinion, the 
need for the dump is absolutely no. You've written yourself, do 
not you write a core dump, because let us make a lot of 
mistakes. Believe me, typing errors will dump less. And on 
their search will be spent even more time

than a set of source code. In addition, since these
procedure, you will include in their programs, then, as the 
source. A If you do not like the starting address of the code? 
So, in our opinion, problems with dumps much more. Now about 
the starting address and length. Length will now be possible to 
specify, as in the starting address is not necessary - all the 
same each proassembliruet under the address that it more 
comfortable. I would like to add one more wish to those who 
will undertake at the suggestion of Maxim optimize the 
procedure. Eliminate the restriction on the coordinate X. 


           *