How to combine eight sketch together in one code

I want know that how to combine eight different sensor sketch together. Is their is any master code or program that call each sketch step by step and run it step wise.

Make each sketch into a function and write the code that calls the functions in the order that is required.

This Simple Merge Demo may give you some ideas.

Also have a look at Planning and Implementing a Program

You will need to be very careful to ensure that there is no overlap between the 8 programs as to which Arduino hardware is used - for example I/O pins or Timers.