I am trying to code for 8051 microcontroller and for "less than (<)" condition I have tried to implement "<" in while loop as per the format but undefined error is occuring. Kindly help me with the solution to remove the error.
You've given far too little detail to even guess at a reason for your error.
Can you give us some meaningful information about what you've got (such as well formatted and commented code) and what your seeing (such as error messages)?
You should also provide information about any debugging you have done along with results of that debugging process.