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I try to find the relationship between MASM.exe and ML.exe in MASM6.11, this is the screen information:
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D:\MASM611\BIN>ml
Microsoft (R) Macro Assembler Version 6.11
Copyright (C) Microsoft Corp 1981-1993.  All rights reserved.

usage: ML [ options ] filelist [ /link linkoptions]
Run "ML /help" or "ML /?" for more info

D:\MASM611\BIN>masm
Microsoft (R) MASM Compatibility Driver Version 6.11
Copyright (C) Microsoft Corp 1993.  All rights reserved.

usage: MASM source(.asm),,

,[;]
Run "MASM /H" for more info
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what is MASM Compatibility Driver?

Perfect answer.
Not only give me correct answer, but also a good place where I can find valuable  information.