Making Multiple Initialized Far Data Segments (34379)

SUMMARY

You can have multiple initialized far-data segments by using the .fardata [name] directive, as documented on page 88 of the "Microsoft Macro Assembler 5.1 Programmers Guide", page 33 of the "Microsoft Macro Assembler Reference" and under topic fardata in the QuickHelp for versions 6.0, 6.0a, and 6.0b. Just make sure that the segments have different names. In versions prior to 6.0, it is possible to leave one of the segments with the default name. With 6.0 and later, the symbol @fardata will be the segment value of the last segment declared with .fardata [name], which may not be the one with the default name.

MORE INFORMATION

The sample program below demonstrates using two intialized far-data segments. The contents of SrcBuff will be copied to DesBuff.

The program size is very large (131k) due to the amount of data that is being declared. It may take a while to link as well.

Sample Code

; Assemble options needed: none

   .model large

   .fardata SrcSeg
SrcBuff  db    65535 dup (65)   ; 1st initialized far segment

   .fardata DestSeg             ; Name 2nd fardata segment BufSeg
DestBuff db    65535 dup (66)

   .code
main:
   MOV  ax, SrcSeg              ; Make ds:si point to SrcBuff
   MOV  ds, ax
   MOV  si, 0

   MOV  ax, DestSeg             ; Make es:di point to DestBuff
   MOV  es, ax
   MOV  di, 0

   MOV  cx, 0ffffh              ; copy full segment

   REP  movsb                   ; automatically inc si & di,
                                ;    dec cx until it is 0
   MOV  ah, 4ch
   INT  21h

   END  main