我现在编写了一个程序  请看
#include<reg52.h>
sbit di=p1^0;
void main()
while(1){ d1=0;
}
出现了这样的问题
Build target 'Target 1'
assembling STARTUP.A51...
A51 MACRO ASSEMBLER V8.01 - SN: Eval Version
COPYRIGHT KEIL ELEKTRONIK GmbH 1987 - 2007
"F:机器人C51BINA51.EXE" "STARTUP.A51" SET (SMALL) DEBUG EP
A51 FATAL ERROR -
  FILE:       STARTUP.A51
  ERROR:      FILE DOES NOT EXIST
A51 TERMINATED.
Target not created
帮我看看该怎么修改 谢谢