Operating System (OS) Basics
An Operating System (OS) is a collection of software that (Abstracts, Arbitrates) manages computer hardware.
Processes and Process Management
A process is basically a program in execution. it can be divided into four sections ─ stack, heap, text, and data. These are following
Stack: The process Stack contains temporary data and local variables.
Heap: This is dynamically allocated memory to a process during its run time.
Data: This contains global and static variables.
Text: This includes the current activity.
The process passes through different states while executing. These states are following,
Start: This is the initial state of the process when created.
Ready: The process is waiting to be assigned to a processor.
Running: The process is executing
Waiting: The process is waiting for user input
Terminated: The process finished the execution or canceled.
Process Control Block (PCB)
PCB keeps all information about every process to track. PCB is identified by a unique process ID (PID).
Process ID: unique identification of process.
State: the current state of the process.
Pointer: A pointer to the parent process.
Program Counter: it is a pointer to the address of the next instruction for the current process.
CPU Register: Process are stored for execution.
CPU Scheduling: To scheduling the process by its priority.
Memory management information: it has information about memory limits.
Accounting Information: This includes the amount of CPU used for process execution, time limits, execution ID, etc.
IO Status Information: This includes a list of I/O devices allocated to the process.
Concurrency is executing a lot of threads at once in Multiple cores. Need more than one core.
Core 1 ->Thread 1
Core 2 ->Thread 2
Core 1 will execute thread 1, Core 2 will execute thread 2
The goal of parallelism is performance.
Concurrency is executing a lot of threads at once in a single core.
Core 1 => T1 -> T2 -> T1 -> T2
Where the core will execute the thread 1 for some time and thread 2 for some time.
The goal of concurrency is a non-blocking application. The application should not hang