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Q44309: DATA Column in BC /A Assembly .LST Listing Is DGROUP Data

Article: Q44309
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom | mspl13_basic
Last Modified: 20-DEC-1989

The BC.EXE compiler supports the /A option, which outputs a listing
(.LST) that shows the assembly-language code that the compiler
generates for each line of the source file.

The "Data" column in this assembly-language code listing is a
hexadecimal value showing how many bytes have been statically
allocated in the default data segment (DGROUP).

This information applies to Microsoft QuickBASIC Versions 4.00,
4.00b, and 4.50 for MS-DOS, to Microsoft BASIC Compiler Versions 6.00
and 6.00b for MS-DOS and MS OS/2, and to Microsoft BASIC PDS Version
7.00 for MS-DOS and MS OS/2.

As a demonstration, compile the following program using the BC /A
option:

   x% = 5              'Allocates 2 bytes
   y! = 100            'Allocates 4 bytes
   z# = 200            'Allocates 8 bytes

The following listing (.LST) file is generated:

Offset  Data    Source Line

 0030   0006    x% = 5              'Allocates 2 bytes
 0030   0006
 0030   0006    y! = 100            'Allocates 4 bytes
 0030   0006
 0030   0006    z# = 200            'Allocates 8 bytes
 0030   0006
 0030   0006
 0030    **            I00002: mov   X%,0005h
 0036    **                    int   35h
 0038    **                    db    06h
 0039    **                    dw    <0000C842>
 003B    **                    int   35h
 003D    **                    db    1Eh
 003E    **                    dw    Y!
 0040    **                    int   3Dh
 0042    **                    int   39h
 0044    **                    db    06h
 0045    **                    dw    <0000000000006940>
 0047    **                    int   39h
 0049    **                    db    1Eh
 004A    **                    dw    Z#
 004C    **                    int   3Dh
 004E    **                    call  B$CENP
 0053   0014

The last entry in the "Data" column shows that a total of 20 bytes (6
+ 2 + 4 + 8 = 20) have been allocated in near data. Note the value is
shown as a hexadecimal number (0014 hex = 20 decimal).

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