Since using xdata, there is used for external RAM. The program file is hex. then, the part of xdata, where is located?
First, you need to read the uVision Getting Started guide, and work through the example projects in it. This will give you a proper introductions to the tools, how they work, and how to use them - rather than just jumping-in blindly at the deep-end! You need to read the following documents - commonly referred to as "the bible" for the 8051 - then you will understand where all this DATA, IDATA, XDATA and stuff comes from: Chapter 1 - 80C51 Family Architecture: http://www.semiconductors.philips.com/acrobat/various/80C51_FAM_ARCH_1.pdf Chapter 2 - 80C51 Family Programmer's Guide and Instruction Set: http://www.semiconductors.philips.com/acrobat/various/80C51_FAM_PROG_GUIDE_1.pdf Chapter 3 - 80C51 Family Hardware Description: http://www.semiconductors.philips.com/acrobat/various/80C51_FAM_HARDWARE_1.pdf