page ,132 title Spy Hunter ;spyhunt.asm -- loader program for Spy Hunter ; The Ross DOS ; 5-27-86 ; From a great southern Engineering / Science college CR equ 13 ;carriage return LF equ 10 ;line feed cseg segment para public 'code' assume cs:cseg,ss:stack ;already set by DOS loader cosmic proc far ;entry point from dos push ds ;set up the stack to xor ax,ax ; the double word vector so the push ax ; far return will go back to dos mov ax,dseg ;set up addressability to mov ds,ax ; the data segment assume ds:dseg ;tell the assembler what I did ;switch to the color monitor push es ;save the extra segment mov ax,0 ;set the mov es,ax ; extra segment to 0 mov bx,449h ;offset mov byte ptr es:[bx],2 ;80-colomn text, no color, CGA pop es ;restore the extra segment ;set video mode mov al,2 ;mode, text 80x25 mov ah,0 ;service 0 of int 10h int 10h ;set video mode ;turn off the screen mov dx,3d8h ;CGA port to set mode mov al,0001b ;set bit 3 off to turn video off out dx,al ;set new mode ;display text mov dx,offset text1 ;data address mov ah,9h ;service 9h of int 21h int 21h ;display text ;turn on the screen mov dx,3d8h ;CGA port to set mode mov al,1001b ;set bit 3 on to turn video on out dx,al ;set new mode ;wait for a key mov ah,8h ;service 8h of int 21h int 21h ;wait for a key ;display text mov dx,offset text2 ;data address mov ah,9h ;service 9h of int 21h int 21h ;display text ;modify memory block allocated by DOS ;the extra segment is already set mov bx,10h ;skip to the end of the PSP mov ah,4ah ;service 4ah of int 21h int 21h ;free memory ;allocate enough memory mov bx,gsize ;memory game program needs mov ah,48h ;service 48h of int 21h int 21h ;allocate memory jnc sabs ;jump if no error jmp err1 ;jump on error sabs: mov buffer,ax ;save allocated buffer segment ;open the program file mov dx,offset file ;data address mov al,0 ;read only mov ah,3dh ;service 3dh int 21h ; of int 21h jnc rtf ;jump if no error jmp err2 ;jump on error ;read the file into memory rtf: mov bx,ax ;bx is the file handle mov ax,ds ;save the data segment mov es,ax ; using the extra segment mov cx,28 ;read in 28 tracks (112 KB) mov ax,buffer ;get the buffer's segment address mov ds,ax ;ds now starts at the buffer rfm: push cx ;save the count mov dx,0 ;buffer offset is 0 mov cx,1000h ;read in 4 KB of data mov ah,3fh ;service 3fh of int 21h int 21h ;read in part of the file pop cx ;restore the count jnc ids ;jump on no error jmp err3 ;jump on error ids: mov ax,ds ;increment the data segment add ax,100h ; by 100h mov ds,ax ; which is 4 KB (absolute address) loop rfm ;loop and finish the count ;restore the data segment mov ax,es ;get the data segment from mov ds,ax ; the extra sement ;close the file mov ah,3eh ;service 3ef of int 21h int 21h ;close the file jnc wuds ;jump on no error jmp err4 ;jump on error ;wait until the drive stops wuds: mov ax,0 ;set the mov es,ax ; extra segment to beginning of memory wait: mov al,es:[43fh] ;get the byte which has the drive status cmp al,0 ;is it zero? jne wait ;no, then loop until it is ;reset the int 8h vector mov ax,0 ;set the mov es,ax ; extra segment to beginning of memory mov bx,8h*4 ;vector offset mov ax,int8h ;offset mov cx,rom ;segment mov es:[bx],ax ;reset vector offset mov es:[bx+2],cx ;reset vector segment ;reset the int 9h vector mov ax,0 ;set the mov es,ax ; extra segment to beginning of memory mov bx,9h*4 ;vector offset mov ax,int9h ;offset mov cx,rom ;segment mov es:[bx],ax ;reset vector offset mov es:[bx+2],cx ;reset vector segment ;reset the int 16h vector mov ax,0 ;set the mov es,ax ; extra segment to beginning of memory mov bx,16h*4 ;vector offset mov ax,int16h ;offset mov cx,rom ;segment mov es:[bx],ax ;reset vector offset mov es:[bx+2],cx ;reset vector segment ;reset the int 1bh vector mov ax,0 ;set the mov es,ax ; extra segment to beginning of memory mov bx,1bh*4 ;vector offset mov ax,int1ch ;offset mov cx,rom ;segment mov es:[bx],ax ;reset vector offset mov es:[bx+2],cx ;reset vector segment ;reset the int 1ch vector mov ax,0 ;set the mov es,ax ; extra segment to beginning of memory mov bx,1ch*4 ;vector offset mov ax,int1ch ;offset mov cx,rom ;segment mov es:[bx],ax ;reset vector offset mov es:[bx+2],cx ;reset vector segment ;move the program down to low memory push ds mov si,0 ;source offset mov di,0ff1h ;destination offset mov ax,buffer ;set the data segment mov ds,ax ; to the buffer mov ax,100h ;set the extra segment mov es,ax ; to low memory mov cx,0e000h ;move 56 KB rep movsb ;move it... mov si,0 ;source offset mov di,0ff1h ;destination offset mov ax,ds ;get the data segment add ax,0e00h ; and inc it mov ds,ax ; 56KB up memory mov ax,es ;get the extra segment add ax,0e00h ; and inc it mov es,ax ; 56KB up memory mov cx,0e000h ;move 56 KB rep movsb ;move it... pop ds ;set the register for the program mov ax,200h ;set the mov ds,ax ; data segment to 200h mov es,ax ; extra segment to 200h mov ax,1e00h ;set the mov ss,ax ; stack segment to 1e00h mov sp,1ff0h ;set the stack pointer to 200h ;run the program sti db 0eah,0,10h,0,1 ;error # 1 -- memory allocation err1: lea dx,error1 ;data address mov ah,9h ;service 9h of int 21h int 21h ;display text jmp done ;error # 2 -- file open error err2: lea dx,error2 ;data address mov ah,9h ;service 9h of int 21h int 21h ;display text jmp done ;error # 3 -- file read error err3: mov ax,es ;restore the mov ds,ax ; data segment lea dx,error3 ;data address mov ah,9h ;service 9h of int 21h int 21h ;display text jmp done ;error # 4 -- file close error err4: lea dx,error4 ;data address mov ah,9h ;service 9h of int 21h int 21h ;display text done: ret ;return to DOS cosmic endp cseg ends dseg segment para public 'data' text1 db 'Spy Hunter',CR,LF db '(C) Copyright 1984 by Bally Midway',CR,LF,CR,LF db 'Broken by The Ross DOS 5-27-86',CR,LF,CR,LF db 'Uses file SPYHUNT.PRG',CR,LF db 'Requires DOS 2.XX or 3.XX',CR,LF db 'Requires 120k of free memory',CR,LF db 'Requires a IBM compatible color graphics adapter',CR,LF,CR,LF db 'This program does the following:',CR,LF db ' gets loaded into high memory',CR,LF db ' allocates 120 KB of RAM (enough to load SPYHUNT.PRG into)',CR,LF db ' loads SPYHUNT.PRG into the allocated block',CR,LF db ' sets interupts 8h,9h,10,16h,1bh,1ch to their initial ROM values',CR,LF db ' moves the program to 0:100h (low memory)',CR,LF db ' sets the registers to their required initial values',CR,LF db ' executes the program by doing a far jump to 100:1000h',CR,LF,CR,LF db 'Since this game provides no method to return to DOS (and infact destroys DOS',CR,LF db 'when moved to low memory), a reboot or power off is required to quit.',CR,LF,CR,LF db 'To stop now, press Crtl-Break.',CR,LF,CR,LF db '* Press any key to continue *','$' text2 db CR,LF,CR,LF db 'Loading...$' file db 'SPYHUNT.PRG',0 error1 db CR,LF,'ERROR: Cannot allocate enough memory',CR,LF,'$' error2 db CR,LF,'ERROR: Cannot open file SPYHUNT.PRG',CR,LF,'$' error3 db CR,LF,'ERROR: Cannot read file SPYHUNT.PRG',CR,LF,'$' error4 db CR,LF,'ERROR: Cannot close file SPYHUNT.PRG',CR,LF,'$' buffer dw ? ;holds the buffer segment int8h dw 0fea5h ;offset of int 1ch int9h dw 0e987h ;offset of int 1ch int16h dw 0e82eh ;offset of int 16h int1bh dw 0ff53h ;offset of int 1ch int1ch dw 0ff53h ;offset of int 1ch rom dw 0f000h ;segment ROM starts at gsize dw 1d4ch+100h ;number of paragraphs game program needs gjump dd ? dseg ends stack segment para stack 'stack' db 64 dup("stack ") ;256 word stack area stack ends end cosmic ;enter at entpt from DOS