D686: Operating Systems for Computer Scientists home (chapter 3)

job

A set of commands or processes executed by a batch system.

user programs

User-level programs, as opposed to system programs.

task

A process, a thread activity, or, generally, a unit of computation on a computer.

process

A program loaded into memory and executing.

program counter

A CPU register indicating the main memory location of the next instruction to load and execute.

text section

The executable code of a program or process.

data section

The data part of a program or process; it contains global variables.

heap section

The section of process memory that is dynamically allocated during process run time; it stores temporary variables.

stack section

The section of process memory that contains the stack; it contains activation records and other temporary data.

activation record

A record created when a function or subroutine is called; added to the stack by the call and removed when the call returns. Contains function parameters, local variables, and the return address.

executable file

A file containing a program that is ready to be loaded into memory and executed.

state

The condition of a process, including its current activity as well as its associated memory and disk contents.

process control block

A per-process kernel data structure containing many pieces of information associated with the process.

task control block

A per-process kernel data structure containing many pieces of information associated with the process.

thread

A process control structure that is an execution location. A process with a single thread executes only one task at a time, while a multithreaded process can execute a task per thread.

process scheduler

A scheduler that selects an available process (possibly from a set of several processes) for execution on a CPU.

degree of multiprogramming

The number of processes in memory.

parent

In a tree data structure, a node that has one or more nodes connected below it.

children

In a tree data structure, nodes connected below another node.

siblings

In a tree data structure, child nodes of the same parent.

I/O-bound process

A process that spends more of its time doing I/O than doing computations

CPU-bound process

A process that spends more time executing on CPU than it does performing I/O

ready queue

The set of processes ready and waiting to execute.

wait queue

In process scheduling, a queue holding processes waiting for an event to occur before they need to be put on CPU.

dispatched

Selected by the process scheduler to be executed next.

CPU scheduler

Kernel routine that selects a thread from the threads that are ready to execute and allocates a core to that thread.

swapping

Moving a process between main memory and a backing store. A process may be swapped out to free main memory temporarily and then swapped back in to continue execution.

context

When describing a process, the state of its execution, including the contents of registers, its program counter, and its memory context, including its stack and heap.

state save

Copying a process's context to save its state in order to pause its execution in preparation for putting another process on the CPU.

state restore

Copying a process's context from its saved location to the CPU registers in preparation for continuing the process's execution.

context switch

The switching of the CPU from one process or thread to another; requires performing a state save of the current process or thread and a state restore of the other.

foreground

Describes a process or thread that is interactive (has input directed to it), such as a window currently selected as active or a terminal window currently selected to receive input.

background

Describes a process or thread that is not currently interactive (has no interactive input directed to it), such as one not currently being used by a user. In the Grand Central Dispatch Apple OS scheduler, the scheduling class representing tasks that are not time sensitive and are not visible to the user.

split-screen

Running multiple foreground processes (e.g., on an iPad) but splitting the screen among the processes.

service

A software entity running on one or more machines and providing a particular type of function to calling clients. In Android, an application component with no user interface; it runs in the background while executing long-running operations or performing work for remote processes.

tree

A data structure that can be used to represent data hierarchically; data values in a tree structure are linked through parent-child relationships.

process identifier (pid)

A unique value for each process in the system that can be used as an index to access various attributes of a process within the kernel.

cascading termination

A technique in which, when a process is ended, all of its children are ended as well.

zombie

A process that has terminated but whose parent has not yet called wait() to collect its state and accounting information.

orphan

The child of a parent process that terminates in a system that does not require a terminating parent to cause its children to be terminated.

interprocess communication (IPC)

Communication between processes.

shared memory

In interprocess communication, a section of memory shared by multiple processes and used for message passing.

message passing

In interprocess communication, a method of sharing data in which messages are sent and received by processes. Packets of information in predefined formats are moved between processes or between computers.

browser

A process that accepts input in the form of a URL (Uniform Resource Locator), or web address, and displays its contents on a screen.

renderer

A process that contains logic for rendering contents (such as web pages) onto a display.

plug-in

An add-on functionality that expands the primary functionality of a process (e.g., a web browser plug-in that displays a type of content different from what the browser can natively handle).

sandbox

A contained environment (e.g., a virtual machine).

producer

A process role in which the process produces information that is consumed by a consumer process

consumer

A process role in which the process consumes information produced by a producer process.

unbounded buffer

A buffer with no practical limit on its memory size.

bounded buffer

A buffer with a fixed size.

direct communication

In interprocess communication, a communication mode in which each process that wants to communicate must explicitly name the recipient or sender of the communication.

blocking

In interprocess communication, a mode of communication in which the sending process is blocked until the message is received by the receiving process or by a mailbox and the receiver blocks until a message is available. In I/O, a request that does not return until the I/O completes.

nonblocking

A type of I/O request that allows the initiating thread to continue while the I/O operation executes. In interprocess communication, a communication mode in which the sending process sends the message and resumes operation and the receiver process retrieves either a valid message or a null if no message is available. In I/O, a request that returns whatever data is currently available, even if it is less than requested.

synchronous

In interprocess communication, a mode of communication in which the sending process is blocked until the message is received by the receiving process or by a mailbox and the receiver blocks until a message is available. In I/O, a request that does not return until the I/O completes.

asynchronous

In I/O, a request that executes while the caller continues execution.

rendezvous

In interprocess communication, when blocking mode is used, the meeting point at which a send is picked up by a receive.