Process Management 1 | Scheduling | A Level | By ZAK

Show understanding of process management:
Process management is a crucial aspect of operating system design, involving the handling of multiple processes by the OS. Understanding this involves examining several key areas:
1. The Concept of Multi-Tasking and a Process:
- Multi-Tasking: This refers to the ability of an operating system to execute multiple tasks or processes simultaneously. It's achieved through mechanisms like time-sharing, where the CPU switches rapidly among different tasks, giving the illusion that they are occurring simultaneously.
- Process: A process is a program in execution. It's more than just the program code (often called the text section); it also includes current activity, including program counter, processor registers, and allocated memory.
2. Process States: Running, Ready, and Blocked:
- Running: When a process is being executed by the CPU, it's in the 'running' state. In this state, it's actively using the CPU.
- Ready: Processes that are prepared to execute but are currently not using the CPU are in the 'ready' state. They are typically waiting in a queue for CPU time.
- Blocked (or Waiting): A process is blocked when it cannot proceed until some external condition, such as I/O completion or resource acquisition, is met. Blocked processes are not using the CPU and cannot proceed until they are no longer blocked.
3. Need for Scheduling:
- The scheduler is a key OS component responsible for deciding which process runs at any given time. It's necessary because multiple processes compete for limited CPU resources. Effective scheduling optimizes CPU utilization, response time, throughput, and other performance metrics.
4. Different Scheduling Routines:
- First Come First Served (FCFS): Processes are executed in the order they arrive in the ready queue. It's simple but can cause short processes to wait for long ones (the "convoy effect").
- Shortest Job First (SJF): This algorithm selects the process with the smallest estimated running time to execute next. It's efficient but requires prior knowledge of the process's duration and can lead to starvation of longer processes.
- Round Robin (RR): This is a preemptive version of FCFS. Each process is assigned a time slice (quantum) and is executed for that time. If it's not finished, it's placed at the back of the queue. This approach is fair and provides a good balance between response time and throughput.
- Shortest Remaining Time: Similar to SJF, but preemptive. The process with the shortest remaining execution time is always chosen next. This can lead to better performance but requires accurate estimations of remaining times.
Each scheduling algorithm has its benefits and drawbacks, and the choice depends on the specific requirements and characteristics of the system and the types of processes it runs. For instance, real-time systems may require more deterministic scheduling algorithms than batch processing systems. The ultimate goal is to maximize CPU utilization and process throughput while minimizing response time and avoiding process starvation.