PsL Monthly 1993 December/PSL Monthly Shareware CD-ROM (December 1993).iso/prgmming/dos/c/flgzero.exe/FLGZERO.LST

File List | 1991-09-16 | 4.7 KB | 113 lines

Microsoft (R) Macro Assembler Version 5.10                  9/16/91 19:16:35
ZERO FLAGS    ; Set display tab to 8 characters                Page     1-1


       1                        PAGE    ,132        ; 80 for narrow printers
       2                        TITLE    ZERO FLAGS    ; Set display tab to 8 characters
       3                        COMMENT    *
       4
       5                Given the base address of a flag word and the number of bits it contains,
       6                this function will set all the bits in the flag word to zero (Note that it works
       7                in byte increments)  The program zeros nothing if no bits are defined, allowing
       8                it to be used with a variable.  It is not designed to work with negative bit counts.
       9
      10                Programmed By:    A. L. Bender, M. D.
      11                        Bender Consulting
      12                        PO Box 8685
      13                        Woodcliff Lake, NJ 07675
      14
      15                Not copyright, freely in public domain.
      16                Not responsible for your use or misuse of this program.
      17
      18                This program was tested with Microsoft c 5.1.  It demonstrates how the bits
      19                are stored in a word.  The enclosed driver program shows how to call it and
      20                how to test it.  Assumes direction flag is set to FORWARD.  (An ok MSC 5.1
      21                Assumption)
      22
      23                The primary purpose of this program is instructional, you can hopefully learn
      24                something about MASM 5.1 Programming from this, especially how to use the
      25                higher level language interface.  See Microsoft MASM 5.1 Update.
      26
      27                Note: This will not execute on an 8086/88 but requires at least an 80186 or V20
      28                You can remove the .186 statement to get it going on the 8086/88 if you need to
      29
      30                The masm call line needs /Dmemmodel={SMALL|MEDIUM|COMPACT|LARGE} as the case
      31                may be to write the proper code.
      32                Example:
      33                masm /Dmemmodel=SMALL /Mx flgzero,,,;  Makes a small model flgzero
      34
      35
      36                *
      37                        .186                    ; Set processor required
      38                        IFDEF        memmodel        ; Did user define it?
      39                %        .MODEL        memmodel,c        ; Use user definition
      40                        ENDIF
      41                        .CODE                    ;Large Model C Program
      42 0000                flgzero        PROC        flagword:PTR BYTE, nrbits:WORD    ; Prologue
      43 0004  8B 46 0A                    MOV        AX,nrbits        ; Get Bit count
      44 0007  85 C0                    TEST        AX,AX            ; If bits are defined (Non Degenerat
                    ive Case)
      45 0009  74 0F                    JZ        @F            ; don't get out
      46 000B  48                    DEC        AX            ; Make count 0...7
      47                        IF        @Cpu NE 0
      48 000C  C1 F8 03                    SAR        AX,3            ; Divide by 8 The easy way
      49                        ENDIF
      50 000F  33 C9                    XOR        CX,CX            ; Prep CX for later
      51 0011  40                    INC        AX            ; Insure fraction of byte is ok
      52 0012  91                    XCHG        CX,AX            ; Copy Quotient of 8 to CX And Zero
                    To AX
Microsoft (R) Macro Assembler Version 5.10                  9/16/91 19:16:35
ZERO FLAGS    ; Set display tab to 8 characters                Page     1-2


      53 0013  57                    PUSH        DI            ; Preserve DI from certain ruin
      54                        IF        @Datasize EQ 1        ;
      55 0014  C4 7E 06                    LES        DI,flagword        ; Get the base address for large dat
                    a
      56                        ENDIF
      57 0017  F3/ AA                    REP STOSB                ; Zero the bytes (See assumption)
      58 0019  5F                    POP        DI            ; Return DI to prior state
      59 001B  CB            @@:        RET                    ; Return to user program
      60 001C                flgzero        ENDP                    ; Epilogue
      61                        END                    ; Epitaph
Microsoft (R) Macro Assembler Version 5.10                  9/16/91 19:16:35
ZERO FLAGS    ; Set display tab to 8 characters                Symbols-1


Segments and Groups:

                N a m e             Length     Align    Combine Class

DGROUP . . . . . . . . . . . . .      GROUP
  _DATA  . . . . . . . . . . . .      0000    WORD    PUBLIC    'DATA'
FLGZERO_TEXT . . . . . . . . . .      001C    WORD    PUBLIC    'CODE'

Symbols:

                N a m e             Type     Value     Attr

FLAGWORD . . . . . . . . . . . .      TEXT  DWORD PTR [BP]+6
flgzero  . . . . . . . . . . . .      F PROC    0000    FLGZERO_TEXT    Global    Length = 001C

MEMMODEL . . . . . . . . . . . .      TEXT  LARGE

NRBITS . . . . . . . . . . . . .      TEXT  WORD PTR [BP]+10

@0 . . . . . . . . . . . . . . .      L NEAR    001A    FLGZERO_TEXT
@CODE  . . . . . . . . . . . . .      TEXT  flgzero_TEXT
@CODESIZE  . . . . . . . . . . .      TEXT  1
@CPU . . . . . . . . . . . . . .      TEXT  259
@DATASIZE  . . . . . . . . . . .      TEXT  1
@FILENAME  . . . . . . . . . . .      TEXT  flgzero
@VERSION . . . . . . . . . . . .      TEXT  510


     68 Source  Lines
     68 Total   Lines
     23 Symbols

  47034 + 391843 Bytes symbol space free

      0 Warning Errors
      0 Severe  Errors