ecm 2026-11a

source/Interrupt List/INT 21 DOS Function Calls/INT 2152 DOS 2 internal SYSVARS GET LIST OF LISTS.txt

@@ -166,13 +166,22 @@ Offset	Size	Description	(Table 01628)
  0Ch	WORD	"smcbLink", not used yet (planned to be an owner segment)
  0Eh	WORD	reserved
 Notes:	the next MCB is at segment (current + size + 1)
-	under DOS 3.1+, the first memory block is the DOS data segment,
+	an MCB may contain all-zeroes in the word 03h. such an MCB may be
+	  created by explicitly allocating an empty memory block, resizing an
+	  existing block to a zero size, or by operations on surrounding MCBs.
+	it is expected that every subsequent MCB is stored at a higher segment
+	  than a prior MCB, ie that the size in word 03h doesn't overflow.
+	under DOS 3.1+, the first block is a segment of DOS data structures,
 	  containing installable drivers, buffers, etc.	 Under DOS 4.0+ it is
 	  divided into subsegments, each with its own memory control block
 	  (see #01633), the first of which is at offset 0000h.
+	the DOS data segment (see INT 2F/AX=1203h) is typically in front of
+	  the first MCB, except in lDOS (optionally) and DR-DOS v7
 	for DOS 5+, blocks owned by DOS may have either "SC" or "SD" in bytes
 	  08h and 09h.	"SC" is system code or locked-out inter-UMB memory,
 	  "SD" is system data, device drivers, etc.
+	MS-DOS v6 LH may allocate excluded UMBs using owner 8 and the name
+	  filled with "HIDDEN  " (two trailing blanks, not NULs)
 	Some versions of DR DOS use only seven characters of the program name,
 	  placing a NUL in the eighth byte.
 	lDOS S MCBs are heavily used by lDOS (lMS-DOS and lRxDOS), only device
@@ -187,6 +196,8 @@ Notes:	the next MCB is at segment (current + size + 1)
 	it is reported that some versions of command.com free memory blocks
 	  used transiently from code running in those very blocks, thus
 	  running in free memory for a bit after this point.
+	lDOS source texts note that splitting MCBs is the only operation that
+	  creates new MCBs, everything else operates on existing MCBs.
 SeeAlso: #01630,#01632,#01633
 
 (Table 01629)

source/Interrupt List/INT 2F Multiplex/internal/INT 2FAE01 DOS 33 internal INSTALLABLE COMMAND EXECUTE.txt

@@ -8,9 +8,11 @@ INT 2F U - DOS 3.3+ internal - INSTALLABLE COMMAND - EXECUTE
 	AX = AE01h
 	DX = magic value FFFFh
 	CH = 00h
-	CL = length of command name (4DOS v4.0)
+	CL = length of command name (4DOS v4.0, MS-DOS v4.01)
 	DS:BX -> command line buffer (see #02977)
 	DS:SI -> command name buffer (see #02978)
+	(at least in MS-DOS v4.01, v6.22) ES:DI -> far callable command.com
+		"sysparse" entrypoint (this is called by APPEND)
 Return: DS:SI buffer updated
 	  if length byte is nonzero, the following bytes contain the uppercase
 	  internal command to execute and the command line buffer contains the
@@ -25,5 +27,10 @@ BUGS:	Novell DOS 7.0's COMMAND.COM (prior to Update 12) will attempt to run
 	  command name buffer to "REM" followed by enough blanks to pad out
 	  the original command's length, which will also work with MS-DOS 6.
 	  (from padgett@tccslr.dnet.mmc.com)
+	FreeCOM and SvarCOM pass DI = 0, and may crash if used with MS-DOS
+	  APPEND because APPEND may try to call into the "sysparse" entry.
+	  FreeCOM's sources (lib/mux_ae.c) comment on the setting DI = 0 as
+	  "Magic value 4dos v4" so it is possible that 4DOS also crashes.
+	FreeCOM passes in CX minus command line length (DS:BX) rather than
+	  plus the command name length (DS:SI).
 SeeAlso: AX=AE00h
-

source/Interrupt List/INT 30 NOT A VECTOR DOS 1 FAR JMP instruction/INT 30 MS Windows 31 PROTECTEDMODE CALLBACK.txt

@@ -1,6 +1,6 @@
 ----------------------------------------------------------------------------
  Unique ID: 30
-   Sort As: 30+01
+   Sort As: 30+02
   Category: W 	MS Windows
       Flag: P 	available only in protected mode
 ----------------------------------------------------------------------------

source/Interrupt List/INT 30 NOT A VECTOR DOS 1 FAR JMP instruction/INT 30 NOT A VECTOR DOS 1 FAR JMP instruction for CPMstyle calls.txt

@@ -1,6 +1,6 @@
 ----------------------------------------------------------------------------
  Unique ID: 30
-   Sort As: 30+02
+   Sort As: 30+01
   Category: D 	DOS kernel
       Flag: n/a
 ----------------------------------------------------------------------------

source/Interrupt List/INT 31 DOS PROTECTED MODE INTERFACE/INT 31 VIRUS Vacsina series INSTALLATION CHECK NOT A VECTOR.txt

@@ -1,6 +1,6 @@
 ----------------------------------------------------------------------------
  Unique ID: 31
-   Sort As: 31+01
+   Sort As: 31+02
   Category: v 	virus/antivirus
       Flag: n/a
 ----------------------------------------------------------------------------

source/Interrupt List/INT 31 DOS PROTECTED MODE INTERFACE/INT 31 overwritten by CPM jump instruction in INT 30.txt

@@ -1,6 +1,6 @@
 ----------------------------------------------------------------------------
  Unique ID: 31
-   Sort As: 31+02
+   Sort As: 31+01
   Category: D 	DOS kernel
       Flag: n/a
 ----------------------------------------------------------------------------