What is the Difference Between Job Scheduling and CPU Scheduling?

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Job scheduling and CPU scheduling are both important aspects of computer operating systems, but they serve different purposes and are also known as long-term and short-term scheduling, respectively.

Job Scheduling:

  • Also known as long-term scheduling.
  • Selects processes from the job pool (or storage) and places them in the ready queue for execution.
  • Regulates the degree of multi-programming (DOM).
  • Controls multi-programming, which involves multiple processes running on the system.

CPU Scheduling:

  • Also known as short-term scheduling.
  • Selects which process has to be executed next and allocates the CPU to that process.
  • Ensures that the most suitable or important process is chosen for processing.
  • Regulates the degree of multi-tasking, which involves switching the CPU among processes.

In summary, job scheduling is responsible for selecting processes from the job pool and placing them in the ready queue for execution, while CPU scheduling is responsible for choosing which process to execute next and allocating the CPU to that process. Both scheduling mechanisms work together to maximize CPU utilization and ensure efficient system performance.

Comparative Table: Job Scheduling vs CPU Scheduling

Here is a table comparing job scheduling and CPU scheduling:

Feature Job Scheduling CPU Scheduling
Focus Long-term planning and selecting processes for execution Short-term allocation of the CPU to processes
Purpose Efficiently manage and execute tasks Make the system more efficient, faster, and fairer
Scheduler Job scheduler or long-term scheduler CPU scheduler or short-term scheduler
Scheduling Objectives Prioritizes jobs with the shortest expected execution time Aims to provide fairness by giving each task an equal chance to execute
System Efficiency Manages the execution of tasks in a distributed manner Makes full use of the CPU and minimizes idle time
Scheduling Criteria Driven by time requirements and execution order Dynamically assigns time slices to tasks based on a fixed amount of time

Job scheduling is focused on long-term planning and selecting processes for execution, while CPU scheduling is concerned with the short-term allocation of the CPU to processes. The main goal of job scheduling is to efficiently manage and execute tasks in a distributed manner, whereas CPU scheduling aims to make the system more efficient, faster, and fairer by minimalizing idle time and ensuring that the CPU is utilized to its fullest extent.