A process contains the program code, stack, data section, and heap. It is represented in the operating system by a process control block that stores information like the process state, number, program counter, registers, and open files. The operating system uses a scheduler to select processes from memory and choose among ready processes, switching between them through context switching that saves the current process control block and loads the next one.

1. Topic:
Processes
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2. Process
• Program that is in execution.
• More than the program code
• Has several parts
• Text Section- Contains the code of the program.
• Stack- Contains Temporary data(Function parameters, local var, Return
address).
• Data Section- Contains Global var
• Heap- Contains dynamic memory allocated during process run time.
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3. Process State
• New- The process is being created.
• Ready- All the resources are
available, process is waiting to be
assigned to a processor
• Running- The CPU is working on this
process's instructions.
• Waiting- The process is waiting for
some event to occur (such as an I/O
completion or reception of a signal).
• Terminated- The process has
finished execution.
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4. Process or Task Control Block
Process is represented in the operating system by a
process control block. Contains many information of a
specific process including these:
• Process State - Ready, Running, waiting, etc.
• Process Number – Process number and parent process
ID.
• Program counter - Indicates the address of the next
instruction to be executed for this process.
• Registers - This state information must be saved when
an interrupt occurs, to allow the process to be
continued correctly in further process.
• List of open files - It saves device allocated, open file
tables, etc.
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5. Process Scheduler & Context Switching
Operating system uses a program scheduler to schedules the processes
of computer system
• LTS - Selects process from job pool and loads them into memory.
• STC - Selects among the processes that are ready to execute.
Context Switching: Saves the current PCB and switch into next PCB. This
task is known as a context switch. Happens by interrupt or some higher
priority task.
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