; This is the DOS 2.0 ELECTRONIC DISK from the example in the DOS 2.0 ; manual. It is now set for 180K of space. Look for the ======> 2 locations ; to change the size. ; ; To include the drive into your system, edit a file called CONFIG.SYS. It ; does not exist on the system supplied by IBM. Create a new file, and type ; in DEVICE=VDISK.COM ; and save the file (must be standard ASCII fornat!). ; make sure you copy VDISK.COM to your boot disk. ; When you boot, the number of disk drives will be determined from the ; switch setting and the ELECTRONIC DISK will be made the next drive letter. ; ; For example, if you have two floppies, the RAM DISK will be Drive C. ; ; ; Assemble this will MASM and link with LINK pgm. ; You must then use the EXE2BIN command, type EXE2BIN VDISK VDISK ; after that, you must rename the new file RENAME VDISK.BIN VDISK.COM ; cseg segment para public 'code' status macro state,err,rc ifidn , or es:word ptr srh_sta_fld[bx],0100h endif ifidn , or es:word ptr srh_sta_fld[bx],0200h endif ifidn , or es:word ptr srh_sta_fld[bx],1000h endif ifnb or es:word ptr srh_sta_fld[bx],rc endif endm ; ; ; srh equ 0 srh_len equ 13 srh_len_fld equ srh srh_ucd_fld equ srh+1 srh_ccd_fld equ srh+2 srh_sta_fld equ srh+3 srh_res_fld equ srh+5 ; md equ srh+srh_len md_len equ 1 dta equ md+md_len dta_len equ 4 count equ dta+dta_len count_len equ 2 ssn equ count+count_len ssn_len equ 2 ; ret_byte equ md+md_len ; bpba_ptr equ dta+dta_len bpda_ptr_len equ 4 ; units equ srh+srh_len units_len equ 1 br_addr_0 equ units+units_len br_addr_1 equ br_addr_0+2 br_addr_len equ 4 bpb_ptr_off equ br_addr_0+br_addr_len bpb_ptr_seg equ bpb_ptr_off+2 ; vdsk proc far assume cs:cseg,es:cseg,ds:cseg begin: start equ $ ; next_dev dd -1 attribute dw 2000h strategy dw dev_strategy interrupt dw dev_int dev_name db 1 db 7 dup(?) ; rh_off dw ? rh_seg dw ?; bpb equ $ dw 512 db 2 dw 1 db 2 dw 112 dw 720 db 0fdh dw 2 ; bpb_ptr dw bpb ; ; current virtual disk information ; total dw ? verify db 0 start_sec dw 0 vdisk_ptr dw 0 user_dta dd ? boot_rec equ $ db 3 dup(0) db 'IBM 2.0' dw 512 db 2 dw 1 db 2 dw 112 dw 720 db 0fdh dw 2 ; ; funtab label byte dw init dw media_check dw build_bpb dw ioctl_in dw input dw nd_input dw in_stat dw in_flush dw output dw out_verify dw out_stat dw out_flush dw ioctl_out ; ; in_save proc near mov ax,es:word ptr dta[bx] mov cs:user_dta,ax mov ax,es:word ptr dta+2[bx] mov cs:user_dta+2,ax mov ax,es:word ptr count[bx] xor ah,ah mov cs:total,ax ret in_save endp ; calc_addr proc near mov ax,cs:start_sec mov cx,20h mul cx mov dx,cs:vdisk_ptr add dx,ax mov ds,dx xor si,si mov ax,cs:total mov cx,512 mul cx or ax,ax jnz move_it mov ax,0ffffh move_it: xchg cx,ax ret calc_addr endp ; sector_read proc near call calc_addr mov es,cs:user_dta+2 mov di,cs:user_dta ; mov ax,di add ax,cx jnc read_copy mov ax,0ffffh sub ax,di mov cx,ax read_copy: rep movsb ret sector_read endp ; sector_write proc near call calc_addr push ds pop es mov di,si mov ds,cs:user_dta+2 mov si,cs:user_dta ; ; mov ax,si add ax,cx jnc write_copy mov ax,0ffffh sub ax,si mov cx,ax write_copy: rep movsb ret sector_write endp ; dev_strategy: mov cs:rh_seg,es mov cs:rh_off,bx ret ; ; ; dev_int: cld push ds push es push ax push bx push cx push dx push di push si ; ; mov al,es:[bx]+2 rol al,1 lea di,funtab xor ah,ah add di,ax jmp word ptr[di] ; ; init: push cs pop dx lea ax,cs:vdisk mov cl,4 ror ax,cl add dx,ax mov cs:vdisk_ptr,dx mov ax,2d00h add dx,ax mov es:word ptr br_addr_0[bx],0 mov es:br_addr_1[bx],dx mov es:byte ptr units[bx],1 lea dx,bpb_ptr mov es:bpb_ptr_off[bx],dx mov es:bpb_ptr_seg[bx],cs mov es,cs:vdisk_ptr xor di,di lea si,boot_rec mov cx,24 rep movsb mov cs:word ptr start_sec,1 mov cs:word ptr total,2 call calc_addr push ds pop es mov di,si xor al,al rep stosb mov ds:byte ptr [si],0fch mov ds:byte ptr 1[si],0ffh mov ds:byte ptr 2[si],0ffh push ds push si mov cs:word ptr start_sec,3 mov cs:word ptr total,2 call calc_addr push ds pop es mov di,si pop si pop ds rep movsb mov cs:word ptr start_sec,5 mov cs:word ptr total,4 call calc_addr xor al,al push ds pop es xor di,di rep stosb mov es,cs:rh_seg mov bx,cs:rh_off status done,moerror,0 jmp exit ; ; media_check: mov es:byte ptr ret_byte[bx],1 status done,moerror,0 jmp exit ; ; ; build_bpb: push es push bx mov cs:word ptr start_sec,0 mov cs:word ptr total,1 call calc_addr push cs pop es lea di,bpb add si,11 mov cx,13 rep movsb pop bx pop es lea dx,bpb mov es:bpba_ptr[bx],dx mov es:bpba_ptr+2[bx],cs mov es:dta[bx],dx mov es:dta+2[bx],cs status done,moerror,0 jmp exit ; ; ioctl_in: ioctl_out: nd_input: in_stat: in_flush: out_stat: out_flush: ; input: call in_save mov ax,es:word ptr ssn[bx] mov cs:start_sec,ax mov ax,es:word ptr count[bx] mov cs:total,ax call sector_read mov bx,cs:rh_off mov es,cs:rh_seg status done,moerror,0 jmp exit ; ; output: call in_save mov ax,es:word ptr ssn[bx] mov cs:start_sec,ax mov ax,es:word ptr count[bx] mov cs:total,ax call sector_write mov bx,cs:rh_off mov es,cs:rh_seg cmp cs:byte ptr verify,0 jz no_verify mov cs:byte ptr verify,0 jmp input no_verify: status done,moerror,0 jmp exit out_verify: mov cs:byte ptr verify,1 jmp output ; ; exit: pop si pop di pop dx pop cx pop bx pop ax pop es pop ds ret e_q_p: if ($-start) mod 16 org ($-start)+16-(($-start) mod 16) endif vdisk equ $ vdsk endp cseg ends end begin