Computer Science Processes and States

The Process Concept

• A program in execution is a process. Processes have multiple parts: program code, current activity (program counter and registers), stack (for temporary data, function parameters, local variables), data section (for global variables), and heap (for memory dynamically allocated during runtime).
• A program is a passive entity stored on disk, a process is active. An executable file must be loaded into memory to become a process.
• Multiple processes can run the same program.

Process State

• Processes transition between different states as they execute.
• The process states are: new, running, waiting, ready, and terminated.
• The new state is when a process is being created.
• The running state is when the process is executing instructions.
• The waiting state is when a process is waiting for an event to occur (e.g., I/O completion).
• The ready state is when a process is waiting to be assigned to a processor.
• The terminated state is when the process has finished execution.

Process Control Block (PCB)

• The PCB stores information about each process.
• This information includes the process state, program counter, CPU registers, CPU scheduling information, memory management information, accounting information, and I/O status information.

Process Termination

• Processes can be terminated by the operating system or by the parent process.
• The parent process can terminate a child process using the abort() system call.
• Reasons for terminating a process include resource exhaustion, task completion, and parent process termination.
• When a process terminates, its resources are deallocated by the operating system.
• If a parent process terminates, its child processes may need to be terminated as well. This is called cascading termination.
• A process that has terminated but is still waiting for its parent to collect its exit status is called a zombie process.
• A process that has lost its parent is called an orphan process.
• The wait() system call allows a parent process to wait for the termination of a child process and collect its exit status.

Multiprocess Architecture - Chrome Browser

• The Google Chrome browser utilizes multiple processes to improve stability and security.
• The browser process manages the user interface, disk and network I/O.
• The renderer process renders web pages, dealing with HTML and JavaScript. Each website opened has its own renderer process, which runs in a sandbox to restrict disk and network I/O and minimize the impact of security exploits.
• Plug-in processes also run separately, one for each type of plug-in.

Interprocess Communication (IPC)

• IPC is a mechanism for processes to communicate with each other.
• Two main models of IPC:
• Shared memory allows processes to share a region of memory.
• Message passing involves processes exchanging messages with each other.

Producer-Consumer Problem

• A classic example of cooperating processes is the producer-consumer problem.
• One or more producer processes generate data that is consumed by one or more consumer processes.
• A buffer is used to store the data, and it can be either unbounded or bounded.

Bounded Buffer Solution

• A bounded buffer solution restricts the buffer size to a fixed number of elements.
• The producer process must wait when the buffer is full, and the consumer process must wait when the buffer is empty.
• The solution can be implemented using shared memory.

Message Passing (cont.)

• An implementation of message passing communication can be implemented using shared memory, a hardware bus, or a network.
• The communication links themselves can be direct or indirect, synchronous or asynchronous, and automatic or explicit buffering.

Direct Communication

• In direct communication, processes explicitly name each other when sending and receiving messages.
• The send() primitive is for sending messages to a specific process.
• The receive () primitive is for receiving messages from a specific process.
• Direct communication links are typically bidirectional.

Indirect Communication

• In indirect communication, processes communicate through mailboxes or ports.
• Each mailbox has a unique ID, and processes can communicate only if they share a mailbox.
• Links can be established by sharing mailboxes.

The Operating System

• The operating system manages processes and provides resources for them.
• It creates and terminates processes, schedules them for execution, and handles interprocess communication.

Explore the concept of processes in computer science, including the various components of a process and the different states it can be in during execution. This quiz will test your understanding of process management and the transitions between states such as new, running, waiting, ready, and terminated.