*** WARNING L1: UNRESOLVED EXTERNAL SYMBOL
SYMBOL: ?C_START MODULE: .\Objects\STARTUP.obj (?C_STARTUP)*** WARNING L2: REFERENCE MADE TO UNRESOLVED EXTERNAL SYMBOL: ?C_START MODULE: .\Objects\STARTUP.obj (?C_STARTUP) ADDRESS: 080AH
I check the following link also.
http://www.keil.com/product/brochures/uv4.pdf - Chapter 6. Creating Embedded Programs.Page 79 explains how to add a source file.
Regards,