Other BIOS Data Area Definitions

ADDRESS  NAME     LENGTH  DESCRIPTION
                  (BYTES)
==========================================================================================
50h:00h  PRTFLG     1     Print screen status byte (=40h:100h) 
                           00h=No Print Screen activity
                           01h=Print Screen operation in progress 
                           ffh=Previous Print Screen operation failed.
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50h:01h  BRKFLG     1     Break Flag 
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50h:02h  ??????     2     (??????)
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50h:04h  ??????     1     Single drive status (Drive A or B)
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50h:05h  ??????     12    (??????)
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50h:10h  ??????     2     BASIC's Segment Address store
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50h:12h  ??????     2     BASIC's Timer Interrupt Vector offset
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50h:14h  ??????     2     BASIC's Timer Interrupt Vector segment
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50h:16h  ??????     2     BASIC's CTRL-Break Interrupt Vector offset
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50h:18h  ??????     2     BASIC's CTRL-Break Interrupt Vector segment
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50h:1Ah  ??????     2     BASIC's Disk Error Interrupt Vector offset
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50h:1Ch  ??????     2     BASIC's Disk Error Interrupt Vector segment
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50h:1Eh  ??????     4     (??????) 
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50h:22h  DSKPRM     11    Disk Parameter table
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50h:2Dh  ??????     1     (??????) 
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50h:2Eh  ??????     4     IBM wants 4 zeros here.
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