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DOS学习入门 & 精彩文章（教学室） » Question about upper memory, extended memory, and expanded memory concepts

Floor1　小笨蛋	Posted 2003-09-19 00:00
初级用户　Posts 5　Credits 119
I read some books saying that upper memory is between 640K and 1024K, but then it also seems like it is made using part of expanded memory? I'm not clear on these concepts, so please give your little brother here some guidance. Thanks in advance~~~~~~~~~

Floor2　GOTOmsdos	Posted 2003-09-20 00:00
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Please go to the DOS Home website ( http://www.doshome.com ) and search for my (GOTOmsdos) related posts.

Floor3　Wengier	Posted 2003-09-21 00:00
系统支持　Posts 10,521　Credits 27,736
Upper memory, that is, UMB, is indeed the memory between 640KB and 1024KB (that is, 1MB); Extended memory, that is, XMS, is memory above 1MB, usually provided for DOS by HIMEM.SYS or a similar memory manager; Expanded memory, that is, EMS, is divided into two types: one is physical expanded memory, and the other is virtual. The former is provided by a dedicated expanded memory board, while the latter is provided by EMM386 by virtualizing EMS using part of XMS.