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Questions and Answers
What is a process?
A program in execution.
What are the components of a process?
Program code, current activity, stack, data section, heap.
Which of the following are states a process can be in?
What does PCB stand for?
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A program is an active entity, while a process is passive.
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What does a process scheduler do?
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What is meant by 'interprocess communication'?
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Which of the following queues are maintained for process scheduling?
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What does a 'ready queue' contain?
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Study Notes
Process Concept
- A process is defined as a program in execution, fundamental to all computation.
- Distinction between programs (passive entities stored on disk) and processes (active entities in memory).
- Execution of programs can be initiated through various means (e.g., GUI, command line).
- A single program can spawn multiple processes, especially in multi-user environments.
- Components of a process include:
- Program code (text section)
- Current activity (program counter, processor registers)
- Stack (temporary data such as function parameters)
- Data section (global variables)
- Heap (dynamically allocated memory)
Process State
- A process undergoes several states during execution:
- New: Process is being created.
- Running: Instructions are actively executed.
- Waiting: Process is pending an event occurrence.
- Ready: Process is prepared to be assigned to a processor.
- Terminated: Execution of the process is complete.
Process Control Block (PCB)
- Contains crucial information for each process, known also as task control block.
- State: Current state of the process (running, waiting, etc).
- Program Counter: Points to the next instruction to execute.
- CPU Registers: Stores contents of process-specific registers.
- CPU Scheduling Information: Holds priorities and scheduling queue details.
- Memory-management Information: Details on memory allocated to the process.
- Accounting Information: Records CPU usage, elapsed time, and time limits.
- I/O Status Information: Lists allocated I/O devices and open files.
Threads
- A standard process typically has a single thread of execution.
- Introduction of multiple threads allows several locations to execute simultaneously, increasing efficiency.
- Each thread requires its own storage, including multiple program counters, and an updated PCB.
Process Representation in Linux
- Processes are represented by the C structure
task_struct, which includes:-
pid_t t_pid: Process identifier -
long state: Current state of the process -
unsigned int time_slice: Time allocated for execution -
struct task_struct *parent: Pointer to parent process -
struct list_head children: Structure managing child processes -
struct files_struct *files: Information about open files -
struct mm_struct *mm: Memory management information
-
Process Scheduling
- Aim is to maximize CPU usage and facilitate rapid switching between processes for effective time-sharing.
- The process scheduler selects processes for execution based on their state and maintains various process queues:
- Job Queue: All processes in the system.
- Ready Queue: Processes in main memory, ready to execute.
- Device Queues: Processes waiting for I/O devices.
- Processes can transition among these queues as their states change.
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Description
Test your knowledge on the fundamental concepts of processes in operating systems. This quiz covers the definitions, distinctions, components, and states of processes during execution. Ideal for students looking to reinforce their understanding of process management.
