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Magnum One (Mid-American Digital) (Disc Manufacturing).iso
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util307.arc
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ENVIRO.PAT
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1987-03-04
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1KB
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34 lines
-------------
-ENVIRON.PAT-
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The following is a patch for COMMAND.COM (IBM-PC) to allow
for a larger environment area. Currently, only 223 bytes total
are allowed for environment string storage, with all data over
223 bytes truncated. Use the following patch to increase the
size of this data area:
1) DEBUG COMMAND.COM (load COMMAND.COM into debugger)
2) S 100 4600 BB 0A 00 B4 48 CD 21 (search for allocation call)
3) Replace the 0A with the new area size factor (in paragraphs).
The string searched for in step 2 is a call to allocate space for the
environment area:
BB 0A 00 MOV BX,0AH ; area size factor=10 decimal
B4 48 MOV AH,48 ; allocation function number
CD 21 INT 21 ; perform allocation call
The area size factor is calculated as (A+4)*16, with A being the area
factor. The default value of 10 decimal yields an environment area of 224
bytes, increasing the value to 20 decimal (14H) will yield an area of 384
bytes; increasing the value to 30 decimal (1EH) will yield 544 bytes.
In DOS 2.10, the area factor byte is plugged in at location ECF.