diff --git a/src/dos/dos_memory.cpp b/src/dos/dos_memory.cpp
index 30de8354..efe8a46c 100644
--- a/src/dos/dos_memory.cpp
+++ b/src/dos/dos_memory.cpp
@@ -16,6 +16,8 @@
  *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  */
 
+/* $Id: dos_memory.cpp,v 1.44 2009-06-08 17:20:02 c2woody Exp $ */
+
 #include "dosbox.h"
 #include "mem.h"
 #include "dos_inc.h"
@@ -45,7 +47,7 @@ static void DOS_CompressMemory(void) {
 void DOS_FreeProcessMemory(Bit16u pspseg) {
 	Bit16u mcb_segment=dos.firstMCB;
 	DOS_MCB mcb(mcb_segment);
-	while (true) {
+	for (;;) {
 		if (mcb.GetPSPSeg()==pspseg) {
 			mcb.SetPSPSeg(MCB_FREE);
 		}
@@ -64,7 +66,7 @@ void DOS_FreeProcessMemory(Bit16u pspseg) {
 	Bit16u umb_start=dos_infoblock.GetStartOfUMBChain();
 	if (umb_start==UMB_START_SEG) {
 		DOS_MCB umb_mcb(umb_start);
-		while (true) {
+		for (;;) {
 			if (umb_mcb.GetPSPSeg()==pspseg) {
 				umb_mcb.SetPSPSeg(MCB_FREE);
 			}
@@ -394,8 +396,8 @@ void DOS_SetupMemory(void) {
 	 * buggy games, which compare against the interrupt table. (probably a 
 	 * broken linked list implementation) */
 	callbackhandler.Allocate(&DOS_default_handler,"DOS default int");
-	Bitu ihseg = 0x70;
-	Bitu ihofs = 0x08;
+	Bit16u ihseg = 0x70;
+	Bit16u ihofs = 0x08;
 	real_writeb(ihseg,ihofs+0x00,(Bit8u)0xFE);	//GRP 4
 	real_writeb(ihseg,ihofs+0x01,(Bit8u)0x38);	//Extra Callback instruction
 	real_writew(ihseg,ihofs+0x02,callbackhandler.Get_callback());  //The immediate word
@@ -434,12 +436,12 @@ void DOS_SetupMemory(void) {
 	if (machine==MCH_TANDY) {
 		/* memory up to 608k available, the rest (to 640k) is used by
 			the tandy graphics system's variable mapping of 0xb800 */
-		mcb.SetSize(0x97FE - DOS_MEM_START - mcb_sizes);
+		mcb.SetSize(0x97FF - DOS_MEM_START - mcb_sizes);
 	} else if (machine==MCH_PCJR) {
 		/* memory from 128k to 640k is available */
 		mcb_devicedummy.SetPt((Bit16u)0x2000);
 		mcb_devicedummy.SetPSPSeg(MCB_FREE);
-		mcb_devicedummy.SetSize(0x9FFE - 0x2000);
+		mcb_devicedummy.SetSize(0x9FFF - 0x2000);
 		mcb_devicedummy.SetType(0x5a);
 
 		/* exclude PCJr graphics region */
@@ -453,6 +455,7 @@ void DOS_SetupMemory(void) {
 		mcb.SetType(0x4d);
 	} else {
 		/* complete memory up to 640k available */
+		/* last paragraph used to add UMB chain to low-memory MCB chain */
 		mcb.SetSize(0x9FFE - DOS_MEM_START - mcb_sizes);
 	}