source: rtems/doc/user/glossary.texi @ 9b4422a2

4.115
Last change on this file since 9b4422a2 was 9b4422a2, checked in by Joel Sherrill <joel.sherrill@…>, on May 3, 2012 at 3:09:24 PM

Remove All CVS Id Strings Possible Using a Script

Script does what is expected and tries to do it as
smartly as possible.

+ remove occurrences of two blank comment lines

next to each other after Id string line removed.

+ remove entire comment blocks which only exited to

contain CVS Ids

+ If the processing left a blank line at the top of

a file, it was removed.

  • Property mode set to 100644
File size: 20.3 KB
Line 
1@c
2@c  COPYRIGHT (c) 1989-2011.
3@c  On-Line Applications Research Corporation (OAR).
4@c  All rights reserved.
5
6@node Glossary, Command and Variable Index, Example Application, Top
7@chapter Glossary
8
9@table @b
10@item active
11A term used to describe an object
12which has been created by an application.
13
14@item aperiodic task
15A task which must execute only at
16irregular intervals and has only a soft deadline.
17
18@item application
19In this document, software which makes
20use of RTEMS.
21
22@item ASR
23see Asynchronous Signal Routine.
24
25@item asynchronous
26Not related in order or timing to
27other occurrences in the system.
28
29@item Asynchronous Signal Routine
30Similar to a hardware
31interrupt except that it is associated with a task and is run in
32the context of a task.  The directives provided by the signal
33manager are used to service signals.
34
35@item awakened
36A term used to describe a task that has
37been unblocked and may be scheduled to the CPU.
38
39@item big endian
40A data representation scheme in which
41the bytes composing a numeric value are arranged such that the
42most significant byte is at the lowest address.
43
44@item bit-mapped
45A data encoding scheme in which each bit
46in a variable is used to represent something different.  This
47makes for compact data representation.
48
49@item block
50A physically contiguous area of memory.
51
52@item blocked
53The task state entered by a task which has
54been previously started and cannot continue execution until the
55reason for waiting has been satisfied.
56
57@item broadcast
58To simultaneously send a message to a
59logical set of destinations.
60
61@item BSP
62see Board Support Package.
63
64@item Board Support Package
65A collection of device
66initialization and control routines specific to a particular
67type of board or collection of boards.
68
69@item buffer
70A fixed length block of memory allocated
71from a partition.
72
73@item calling convention
74The processor and compiler
75dependent rules which define the mechanism used to invoke
76subroutines in a high-level language.  These rules define the
77passing of arguments, the call and return mechanism, and the
78register set which must be preserved.
79
80@item Central Processing Unit
81This term is equivalent to
82the terms processor and microprocessor.
83
84@item chain
85A data structure which allows for efficient
86dynamic addition and removal of elements.  It differs from an
87array in that it is not limited to a predefined size.
88
89@item coalesce
90The process of merging adjacent holes into
91a single larger hole.  Sometimes this process is referred to as
92garbage collection.
93
94@item Configuration Table
95A table which contains
96information used to tailor RTEMS for a particular application.
97
98@item context
99All of the processor registers and
100operating system data structures associated with a task.
101
102@item context switch
103Alternate term for task switch.
104Taking control of the processor from one task and transferring
105it to another task.
106
107@item control block
108A data structure used by the
109executive to define and control an object.
110
111@item core
112When used in this manual, this term refers to
113the internal executive utility functions.  In the interest of
114application portability, the core of the executive should not be
115used directly by applications.
116
117@item CPU
118An acronym for Central Processing Unit.
119
120@item critical section
121A section of code which must be
122executed indivisibly.
123
124@item CRT
125An acronym for Cathode Ray Tube.  Normally used
126in reference to the man-machine interface.
127
128@item deadline
129A fixed time limit by which a task must
130have completed a set of actions.  Beyond this point, the results
131are of reduced value and may even be considered useless or
132harmful.
133
134@item device
135A peripheral used by the application that
136requires special operation software.  See also device driver.
137
138@item device driver
139Control software for special
140peripheral devices used by the application.
141
142@item directives
143RTEMS' provided routines that provide
144support mechanisms for real-time applications.
145
146@item dispatch
147The act of loading a task's context onto
148the CPU and transferring control of the CPU to that task.
149
150@item dormant
151The state entered by a task after it is
152created and before it has been started.
153
154@item Device Driver Table
155A table which contains the
156entry points for each of the configured device drivers.
157
158@item dual-ported
159A term used to describe memory which
160can be accessed at two different addresses.
161
162@item embedded
163An application that is delivered as a
164hidden part of a larger system.  For example, the software in a
165fuel-injection control system is an embedded application found
166in many late-model automobiles.
167
168@item envelope
169A buffer provided by the MPCI layer to
170RTEMS which is used to pass messages between nodes in a
171multiprocessor system.  It typically contains routing
172information needed by the MPCI.  The contents of an envelope are
173referred to as a packet.
174
175@item entry point
176The address at which a function or task
177begins to execute.  In C, the entry point of a function is the
178function's name.
179
180@item events
181A method for task communication and
182synchronization. The directives provided by the event manager
183are used to service events.
184
185@item exception
186A synonym for interrupt.
187
188@item executing
189The task state entered by a task after it
190has been given control of the CPU.
191
192@item executive
193In this document, this term is used to
194referred to RTEMS.  Commonly, an executive is a small real-time
195operating system used in embedded systems.
196
197@item exported
198An object known by all nodes in a
199multiprocessor system.  An object created with the GLOBAL
200attribute will be exported.
201
202@item external address
203The address used to access
204dual-ported memory by all the nodes in a system which do not own
205the memory.
206
207@item FIFO
208An acronym for First In First Out.
209
210@item First In First Out
211A discipline for manipulating entries in a data structure.
212
213@item floating point coprocessor
214A component used in
215computer systems to enhance performance in mathematically
216intensive situations.  It is typically viewed as a logical
217extension of the primary processor.
218
219@item freed
220A resource that has been released by the
221application to RTEMS.
222
223@item global
224An object that has been created with the
225GLOBAL attribute and exported to all nodes in a multiprocessor
226system.
227
228@item handler
229The equivalent of a manager, except that it
230is internal to RTEMS and forms part of the core.  A handler is a
231collection of routines which provide a related set of functions.
232For example, there is a handler used by RTEMS to manage all
233objects.
234
235@item hard real-time system
236A real-time system in which a
237missed deadline causes the worked performed to have no value or
238to result in a catastrophic effect on the integrity of the
239system.
240
241@item heap
242A data structure used to dynamically allocate
243and deallocate variable sized blocks of memory.
244
245@item heterogeneous
246A multiprocessor computer system composed of dissimilar processors.
247
248@item homogeneous
249A multiprocessor computer system composed of a single type of processor.
250
251@item ID
252An RTEMS assigned identification tag used to
253access an active object.
254
255@item IDLE task
256A special low priority task which assumes
257control of the CPU when no other task is able to execute.
258
259@item interface
260A specification of the methodology used
261to connect multiple independent subsystems.
262
263@item internal address
264The address used to access
265dual-ported memory by the node which owns the memory.
266
267@item interrupt
268A hardware facility that causes the CPU
269to suspend execution, save its status, and transfer control to a
270specific location.
271
272@item interrupt level
273A mask used to by the CPU to
274determine which pending interrupts should be serviced.  If a
275pending interrupt is below the current interrupt level, then the
276CPU does not recognize that interrupt.
277
278@item Interrupt Service Routine
279An ISR is invoked by the
280CPU to process a pending interrupt.
281
282@item I/O
283An acronym for Input/Output.
284
285@item ISR
286An acronym for Interrupt Service Routine.
287
288@item kernel
289In this document, this term is used as a
290synonym for executive.
291
292@item list
293A data structure which allows for dynamic
294addition and removal of entries.  It is not statically limited
295to a particular size.
296
297@item little endian
298A data representation scheme in which
299the bytes composing a numeric value are arranged such that the
300least significant byte is at the lowest address.
301
302@item local
303An object which was created with the LOCAL
304attribute and is accessible only on the node it was created and
305resides upon.  In a single processor configuration, all objects
306are local.
307
308@item local operation
309The manipulation of an object which
310resides on the same node as the calling task.
311
312@item logical address
313An address used by an application.
314In a system without memory management, logical addresses will
315equal physical addresses.
316
317@item loosely-coupled
318A multiprocessor configuration
319where shared memory is not used for communication.
320
321@item major number
322The index of a device driver in the
323Device Driver Table.
324
325@item manager
326A group of related RTEMS' directives which
327provide access and control over resources.
328
329@item memory pool
330Used interchangeably with heap.
331
332@item message
333A sixteen byte entity used to communicate
334between tasks.  Messages are sent to message queues and stored
335in message buffers.
336
337@item message buffer
338A block of memory used to store
339messages.
340
341@item message queue
342An RTEMS object used to synchronize
343and communicate between tasks by transporting messages between
344sending and receiving tasks.
345
346@item Message Queue Control Block
347A data structure associated with each message queue used by RTEMS
348to manage that message queue.
349
350@item minor number
351A numeric value passed to a device
352driver, the exact usage of which is driver dependent.
353
354@item mode
355An entry in a task's control block that is
356used to determine if the task allows preemption, timeslicing,
357processing of signals, and the interrupt disable level used by
358the task.
359
360@item MPCI
361An acronym for Multiprocessor Communications
362Interface Layer.
363
364@item multiprocessing
365The simultaneous execution of two
366or more processes by a multiple processor computer system.
367
368@item multiprocessor
369A computer with multiple CPUs
370available for executing applications.
371
372@item Multiprocessor Communications Interface Layer
373A set
374of user-provided routines which enable the nodes in a
375multiprocessor system to communicate with one another.
376
377@item Multiprocessor Configuration Table
378The data structure defining the characteristics of the multiprocessor
379target system with which RTEMS will communicate.
380
381@item multitasking
382The alternation of execution amongst a
383group of processes on a single CPU.  A scheduling algorithm is
384used to determine which process executes at which time.
385
386@item mutual exclusion
387A term used to describe the act of
388preventing other tasks from accessing a resource simultaneously.
389
390@item nested
391A term used to describe an ASR that occurs
392during another ASR or an ISR that occurs during another ISR.
393
394@item node
395A term used to reference a processor running
396RTEMS in a multiprocessor system.
397
398@item non-existent
399The state occupied by an uncreated or
400deleted task.
401
402@item numeric coprocessor
403A component used in computer
404systems to enhance performance in mathematically intensive
405situations.  It is typically viewed as a logical extension of
406the primary processor.
407
408@item object
409In this document, this term is used to refer
410collectively to tasks, timers, message queues, partitions,
411regions, semaphores, ports, and rate monotonic periods.  All
412RTEMS objects have IDs and user-assigned names.
413
414@item object-oriented
415A term used to describe systems
416with common mechanisms for utilizing a variety of entities.
417Object-oriented systems shield the application from
418implementation details.
419
420@item operating system
421The software which controls all
422the computer's resources and provides the base upon which
423application programs can be written.
424
425@item overhead
426The portion of the CPUs processing power
427consumed by the operating system.
428
429@item packet
430A buffer which contains the messages passed
431between nodes in a multiprocessor system.  A packet is the
432contents of an envelope.
433
434@item partition
435An RTEMS object which is used to allocate
436and deallocate fixed size blocks of memory from an dynamically
437specified area of memory.
438
439@item Partition Control Block
440A data structure associated
441with each partition used by RTEMS to manage that partition.
442
443@item pending
444A term used to describe a task blocked
445waiting for an event, message, semaphore, or signal.
446
447@item periodic task
448A task which must execute at regular
449intervals and comply with a hard deadline.
450
451@item physical address
452The actual hardware address of a
453resource.
454
455@item poll
456A mechanism used to determine if an event has
457occurred by periodically checking for a particular status.
458Typical events include arrival of data, completion of an action,
459and errors.
460
461@item pool
462A collection from which resources are
463allocated.
464
465@item portability
466A term used to describe the ease with
467which software can be rehosted on another computer.
468
469@item posting
470The act of sending an event, message,
471semaphore, or signal to a task.
472
473@item preempt
474The act of forcing a task to relinquish the
475processor and dispatching to another task.
476
477@item priority
478A mechanism used to represent the relative
479importance of an element in a set of items.  RTEMS uses priority
480to determine which task should execute.
481
482@item priority inheritance
483An algorithm that calls for
484the lower priority task holding a resource to have its priority
485increased to that of the highest priority task blocked waiting
486for that resource.  This avoids the problem of priority
487inversion.
488
489@item priority inversion
490A form of indefinite
491postponement which occurs when a high priority tasks requests
492access to shared resource currently allocated to low priority
493task.  The high priority task must block until the low priority
494task releases the resource.
495
496@item processor utilization
497The percentage of processor
498time used by a task or a set of tasks.
499
500@item proxy
501An RTEMS control structure used to represent,
502on a remote node, a task which must block as part of a remote
503operation.
504
505@item Proxy Control Block
506A data structure associated
507with each proxy used by RTEMS to manage that proxy.
508
509@item PTCB
510An acronym for Partition Control Block.
511
512@item PXCB
513An acronym for Proxy Control Block.
514
515@item quantum
516The application defined unit of time in
517which the processor is allocated.
518
519@item queue
520Alternate term for message queue.
521
522@item QCB
523An acronym for Message Queue Control Block.
524
525@item ready
526A task occupies this state when it is
527available to be given control of the CPU.
528
529@item real-time
530A term used to describe systems which are
531characterized by requiring deterministic response times to
532external stimuli.  The external stimuli require that the
533response occur at a precise time or the response is incorrect.
534
535@item reentrant
536A term used to describe routines which do
537not modify themselves or global variables.
538
539@item region
540An RTEMS object which is used to allocate
541and deallocate variable size blocks of memory from a dynamically
542specified area of memory.
543
544@item Region Control Block
545A data structure associated
546with each region used by RTEMS to manage that region.
547
548@item registers
549Registers are locations physically
550located within a component, typically used for device control or
551general purpose storage.
552
553@item remote
554Any object that does not reside on the local
555node.
556
557@item remote operation
558The manipulation of an object
559which does not reside on the same node as the calling task.
560
561@item return code
562Also known as error code or return
563value.
564
565@item resource
566A hardware or software entity to which
567access must be controlled.
568
569@item resume
570Removing a task from the suspend state.  If
571the task's state is ready following a call to the
572@code{@value{DIRPREFIX}task_resume}
573directive, then the task is available for scheduling.
574
575@item return code
576A value returned by RTEMS directives to
577indicate the completion status of the directive.
578
579@item RNCB
580An acronym for Region Control Block.
581
582@item round-robin
583A task scheduling discipline in which
584tasks of equal priority are executed in the order in which they
585are made ready.
586
587@item RS-232
588A standard for serial communications.
589
590@item running
591The state of a rate monotonic timer while
592it is being used to delineate a period.  The timer exits this
593state by either expiring or being canceled.
594
595@item schedule
596The process of choosing which task should
597next enter the executing state.
598
599@item schedulable
600A set of tasks which can be guaranteed
601to meet their deadlines based upon a specific scheduling
602algorithm.
603
604@item segments
605Variable sized memory blocks allocated
606from a region.
607
608@item semaphore
609An RTEMS object which is used to
610synchronize tasks and provide mutually exclusive access to
611resources.
612
613@item Semaphore Control Block
614A data structure associated
615with each semaphore used by RTEMS to manage that semaphore.
616
617@item shared memory
618Memory which is accessible by
619multiple nodes in a multiprocessor system.
620
621@item signal
622An RTEMS provided mechanism to communicate
623asynchronously with a task.  Upon reception of a signal, the ASR
624of the receiving task will be invoked.
625
626@item signal set
627A thirty-two bit entity which is used to
628represent a task's collection of pending signals and the signals
629sent to a task.
630
631@item SMCB
632An acronym for Semaphore Control Block.
633
634@item soft real-time system
635A real-time system in which a
636missed deadline does not compromise the integrity of the system.
637
638@item sporadic task
639A task which executes at irregular
640intervals and must comply with a hard deadline.  A minimum
641period of time between successive iterations of the task can be
642guaranteed.
643
644@item stack
645A data structure that is managed using a Last
646In First Out (LIFO) discipline.  Each task has a stack
647associated with it which is  used to store return information
648and local variables.
649
650@item status code
651Also known as error code or return
652value.
653
654@item suspend
655A term used to describe a task that is not
656competing for the CPU because it has had a
657@code{@value{DIRPREFIX}task_suspend} directive.
658
659@item synchronous
660Related in order or timing to other
661occurrences in the system.
662
663@item system call
664In this document, this is used as an
665alternate term for directive.
666
667@item target
668The system on which the application will
669ultimately execute.
670
671@item task
672A logically complete thread of execution.  The
673CPU is allocated among the ready tasks.
674
675@item Task Control Block
676A data structure associated with
677each task used by RTEMS to manage that task.
678
679@item task switch
680Alternate terminology for context
681switch.  Taking control of the processor from one task and given
682to another.
683
684@item TCB
685An acronym for Task Control Block.
686
687@item tick
688The basic unit of time used by RTEMS.  It is a
689user-configurable number of microseconds.  The current tick
690expires when the @code{@value{DIRPREFIX}clock_tick}
691directive is invoked.
692
693@item tightly-coupled
694A multiprocessor configuration
695system which communicates via shared memory.
696
697@item timeout
698An argument provided to a number of
699directives which determines the maximum length of time an
700application task is willing to wait to acquire the resource if
701it is not immediately available.
702
703@item timer
704An RTEMS object used to invoke subprograms at
705a later time.
706
707@item Timer Control Block
708A data structure associated
709with each timer used by RTEMS to manage that timer.
710
711@item timeslicing
712A task scheduling discipline in which
713tasks of equal priority are executed for a specific period of
714time before being preempted by another task.
715
716@item timeslice
717The application defined unit of time in
718which the processor is allocated.
719
720@item TMCB
721An acronym for Timer Control Block.
722
723@item transient overload
724A temporary rise in system
725activity which may cause deadlines to be missed.  Rate Monotonic
726Scheduling can be used to determine if all deadlines will be met
727under transient overload.
728
729@item user extensions
730Software routines provided by the
731application to enhance the functionality of RTEMS.
732
733@item User Extension Table
734A table which contains the
735entry points for each user extensions.
736
737@item User Initialization Tasks Table
738A table which
739contains the information needed to create and start each of the
740user initialization tasks.
741
742@item user-provided
743Alternate term for user-supplied.
744This term is used to designate any software routines which must
745be written by the application designer.
746
747@item user-supplied
748Alternate term for user-provided.
749This term is used to designate any software routines which must
750be written by the application designer.
751
752@item vector
753Memory pointers used by the processor to
754fetch the address of routines which will handle various
755exceptions and interrupts.
756
757@item wait queue
758The list of tasks blocked pending the
759release of a particular resource.  Message queues, regions, and
760semaphores have a wait queue associated with them.
761
762@item yield
763When a task voluntarily releases control of the processor.
764
765@end table
766
Note: See TracBrowser for help on using the repository browser.