Complex sentence: In first come first serve scheme which ever job that comes first will be forwarded for execution but in this scheme, once a job arrives at the system, the job will not be scheduled until and unless enough processors are available for the execution of the job.
Split into simpler sentences: In first come first serve scheme which ever job that comes first will be forwarded for execution. As per the scheme, once a job arrives at the system, the job will not be scheduled until and unless enough processors are available for the execution of the job.