primary question

What's the differece between DATA(BIT,IDATA,...) and DS
?

 RE: primary question

Have you tried looking up each term in the assembler Manual, and comparing their descriptions?

http://www.keil.com/support/man/docs/a51/a51_st_ds.htm

http://www.keil.com/support/man/docs/a51/a51_st_data.htm

etc...

 RE: primary question

But,when do i use them,i just can't understand yet?!

 bible time

here are the links to "the bible"
Chapter 1 - 80C51 Family Architecture:
Chapter 1 - 80C51 Family Architecture:
http://www.nxp.com/acrobat_download/various/80C51_FAM_ARCH_1.pdf
Chapter 2 - 80C51 Family Programmer's Guide and Instruction Set:
http://www.nxp.com/acrobat_download/various/80C51_FAM_PROG_GUIDE_1.pdf
Chapter 3 - 80C51 Family Hardware Description:
http://www.nxp.com/acrobat_download/various/80C51_FAM_HARDWARE_1.pdf

 RE: bible time - not this time

The so-called "bible" doesn't tell you how to write programs in assembler, nor how to use any particular assembler.

Unfortunately for the OP (and others like him), everything on the Keil site seems to be focussed on 'C' - there is precious little on how to write programs in assembler...

Maybe check-out the Book list:

http://www.keil.com/books/8051books.asp

 RE: bible time - this time

The so-called "bible" doesn't tell you how to write programs in assembler, nor how to use any particular assembler.
correct, but it does give an insight as to
What's the differece between DATA(BIT,IDATA,...)

Erik

 RE: bible time - this time

Yes: familiarity with the so-called "bible" is necessary, but not sufficient!