Computer Science: Programs and Processes

Program vs Process

• A program is an inactive unit, stored as a file on a disk, e.g., a job.
• A process is an active unit that needs resources (CPU, RAM, etc.) to execute, e.g., a task.

Processor Manager

• The processor manager allocates CPU resources to incoming jobs for execution.
• Its key function is to ensure efficient and fair process execution.

Components of Process Layout

• Memory Layout: Defines how a process occupies memory (text, data, heap, stack).
• Scheduler: Manages the execution order of processes (long-term, short-term, medium-term).
• Dispatcher: Switches the CPU between processes (context switching).
• Timer: Keeps track of process execution time.
• Process Control Block (PCB): Stores information about each process (process identification, state, etc.).
• Process States: Define the different stages a process can be in (new, ready, running, waiting).
• Process Scheduling: Algorithms and strategies for selecting and executing processes.

Memory Layout of a Process

• Text Section: Contains the executable code of the program.
• Data Section: Holds global and static variables used by the program.
• Heap Section: Dynamically allocated memory used during runtime.
• Stack Section: Temporary storage used for function calls and local variables.

Process Scheduler

• Long-Term Scheduler (Job Scheduler): Selects jobs from a queue of incoming jobs (secondary memory) and places them in the ready queue.
• Short-Term Scheduler (CPU Scheduler): Assigns the CPU to execute processes from the ready queue; determines which process will run next.
• **Medium-Term Scheduler:**Handles swapping processes in and out of memory.

Dispatcher

• The dispatcher handles switching the CPU to the next process chosen by the short-term scheduler (context switching).

Timer

• The timer tracks the time each process has been running or the allocated time for each process.

Process Control Block (PCB)

• The PCB is a data structure containing information about each process.
• It is crucial for process management, especially during context switching.
• The PCB is used by the CPU during runtime.

Components of PCB

• Process Identification: Assigns a unique ID for easy identification.
• Process State: Indicates the current status of the process (new, ready, running, waiting, etc.).

Explore the differences between programs and processes in this quiz, which covers key concepts such as the processor manager and components of process layout. Test your understanding of memory management, scheduling, and process states crucial in computer science.