1. Long term Scheduler
In a batch processing system several processes arrive at the same time and they are spooled into a mass storage device. The Long-Term Scheduler or better called as Job Scheduler selects the processes from the spool and loads them into the memory.
The Sort-Term Scheduler or better called CPU Scheduler selects the processes that are ready to execute (processes that are in the ready queue) and allocates them CPU.
The Mid-Term Scheduler is used to swap a process to and from virtual memory and allocate CPU for the same.
Hence, it is the long term scheduler that decides which program should be admitted and which should exit the system.