In an operating system, what are the main functions of the scheduler?

Introduction / Context:
The scheduler is a key part of an operating system that enables multitasking. It decides which process or thread should run at any given moment on the CPU. Understanding the scheduler functions is important for analysing system performance, responsiveness and fairness among competing processes.

Given Data / Assumptions:

Many processes or threads are ready to execute at the same time.
The CPU can execute only one thread per core at any instant.
The operating system must have a policy to decide which ready entity runs next.
The question asks about the main responsibilities of the scheduler, not about compilation or hardware repair.

Concept / Approach:
The scheduler maintains one or more ready queues of processes or threads that are prepared to run. Based on a scheduling algorithm such as round robin, priority scheduling or multilevel feedback queues, it chooses the next runnable entity. The dispatcher then performs a context switch so that the chosen entity runs on the CPU. The scheduler aims to balance goals such as throughput, response time, fairness and meeting deadlines in real time systems.

Step-by-Step Solution:
Step 1: When a running process blocks, terminates or exhausts its time slice, the scheduler must choose another ready process or thread to run. Step 2: The scheduler consults its data structures, often priority based queues, to select the next candidate according to the chosen scheduling policy. Step 3: It then passes this decision to the dispatcher, which performs the technical details of the context switch. Step 4: Over time, the scheduler decisions determine how CPU time is divided among all runnable entities and thus strongly influence system performance and perceived responsiveness. Step 5: Therefore, the main function of the scheduler is selecting and ordering execution of ready processes or threads and allocating CPU time among them.

Verification / Alternative check:
Operating system texts describe short term, medium term and long term schedulers, but all share the common responsibility of choosing which jobs or processes should run or stay in memory. Compilation, device driver management and hardware diagnostics may be parts of the system or tools, but they are not the primary roles of the scheduler.

Why Other Options Are Wrong:
Translating high level code into machine code is the job of a compiler, not the process scheduler.
While schedulers may consider I O bound versus CPU bound behaviour, dedicated driver management is handled by device drivers and related subsystems, not by the core scheduler alone.
Automatic hardware repair is outside the scope of operating system scheduling and is often handled by separate management tools or firmware.

Common Pitfalls:
Students sometimes confuse the scheduler with other system components such as the memory manager or file system. Another pitfall is to ignore different levels of scheduling, such as job scheduling versus CPU scheduling, but the core idea in all cases is selecting and ordering work for execution.

Final Answer:
The scheduler main function is to choose which ready processes or threads should run on the CPU, in what order and for how long, according to a defined scheduling policy.