From ae68ff085724dd35d60151bd153e80b8b0776873 Mon Sep 17 00:00:00 2001 From: Joel Sherrill Date: Tue, 27 May 1997 12:40:11 +0000 Subject: Initial revision --- doc/user/glossary.texi | 772 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 772 insertions(+) create mode 100644 doc/user/glossary.texi (limited to 'doc/user/glossary.texi') diff --git a/doc/user/glossary.texi b/doc/user/glossary.texi new file mode 100644 index 0000000000..58b57061f0 --- /dev/null +++ b/doc/user/glossary.texi @@ -0,0 +1,772 @@ +@c +@c COPYRIGHT (c) 1996. +@c On-Line Applications Research Corporation (OAR). +@c All rights reserved. +@c + +@ifinfo +@node Glossary, Command and Variable Index, Example Application, Top +@end ifinfo +@chapter Glossary + +@table @b +@item active +A term used to describe an object +which has been created by an application. + +@item aperiodic task +A task which must execute only at +irregular intervals and has only a soft deadline. + +@item application +In this document, software which makes +use of RTEMS. + +@item ASR +see Asynchronous Signal Routine. + +@item asynchronous +Not related in order or timing to +other occurrences in the system. + +@item Asynchronous Signal Routine +Similar to a hardware +interrupt except that it is associated with a task and is run in +the context of a task. The directives provided by the signal +manager are used to service signals. + +@item awakened +A term used to describe a task that has +been unblocked and may be scheduled to the CPU. + +@item big endian +A data representation scheme in which +the bytes composing a numeric value are arranged such that the +most significant byte is at the lowest address. + +@item bit-mapped +A data encoding scheme in which each bit +in a variable is used to represent something different. This +makes for compact data representation. + +@item block +A physically contiguous area of memory. + +@item blocked +The task state entered by a task which has +been previously started and cannot continue execution until the +reason for waiting has been satisfied. + +@item broadcast +To simultaneously send a message to a +logical set of destinations. + +@item BSP +see Board Support Package. + +@item Board Support Package +A collection of device +initialization and control routines specific to a particular +type of board or collection of boards. + +@item buffer +A fixed length block of memory allocated +from a partition. + +@item calling convention +The processor and compiler +dependent rules which define the mechanism used to invoke +subroutines in a high-level language. These rules define the +passing of arguments, the call and return mechanism, and the +register set which must be preserved. + +@item Central Processing Unit +This term is equivalent to +the terms processor and microprocessor. + +@item chain +A data structure which allows for efficient +dynamic addition and removal of elements. It differs from an +array in that it is not limited to a predefined size. + +@item coalesce +The process of merging adjacent holes into +a single larger hole. Sometimes this process is referred to as +garbage collection. + +@item Configuration Table +A table which contains +information used to tailor RTEMS for a particular application. + +@item context +All of the processor registers and +operating system data structures associated with a task. + +@item context switch +Alternate term for task switch. +Taking control of the processor from one task and transferring +it to another task. + +@item control block +A data structure used by the +executive to define and control an object. + +@item core +When used in this manual, this term refers to +the internal executive utility functions. In the interest of +application portability, the core of the executive should not be +used directly by applications. + +@item CPU +An acronym for Central Processing Unit. + +@item critical section +A section of code which must be +executed indivisibly. + +@item CRT +An acronym for Cathode Ray Tube. Normally used +in reference to the man-machine interface. + +@item deadline +A fixed time limit by which a task must +have completed a set of actions. Beyond this point, the results +are of reduced value and may even be considered useless or +harmful. + +@item device +A peripheral used by the application that +requires special operation software. See also device driver. + +@item device driver +Control software for special +peripheral devices used by the application. + +@item directives +RTEMS' provided routines that provide +support mechanisms for real-time applications. + +@item dispatch +The act of loading a task's context onto +the CPU and transferring control of the CPU to that task. + +@item dormant +The state entered by a task after it is +created and before it has been started. + +@item Device Driver Table +A table which contains the +entry points for each of the configured device drivers. + +@item dual-ported +A term used to describe memory which +can be accessed at two different addresses. + +@item embedded +An application that is delivered as a +hidden part of a larger system. For example, the software in a +fuel-injection control system is an embedded application found +in many late-model automobiles. + +@item envelope +A buffer provided by the MPCI layer to +RTEMS which is used to pass messages between nodes in a +multiprocessor system. It typically contains routing +information needed by the MPCI. The contents of an envelope are +referred to as a packet. + +@item entry point +The address at which a function or task +begins to execute. In C, the entry point of a function is the +function's name. + +@item events +A method for task communication and +synchronization. The directives provided by the event manager +are used to service events. + +@item exception +A synonym for interrupt. + +@item executing +The task state entered by a task after it +has been given control of the CPU. + +@item executive +In this document, this term is used to +referred to RTEMS. Commonly, an executive is a small real-time +operating system used in embedded systems. + +@item exported +An object known by all nodes in a +multiprocessor system. An object created with the GLOBAL +attribute will be exported. + +@item external address +The address used to access +dual-ported memory by all the nodes in a system which do not own +the memory. + +@item FIFO +An acronym for First In First Out. + +@item First In First Out +A discipline for manipulating +entries in a data structure. + +@item floating point coprocessor +A component used in +computer systems to enhance performance in mathematically +intensive situations. It is typically viewed as a logical +extension of the primary processor. + +@item freed +A resource that has been released by the +application to RTEMS. + +@item global +An object that has been created with the +GLOBAL attribute and exported to all nodes in a multiprocessor +system. + +@item handler +The equivalent of a manager, except that it +is internal to RTEMS and forms part of the core. A handler is a +collection of routines which provide a related set of functions. +For example, there is a handler used by RTEMS to manage all +objects. + +@item hard real-time system +A real-time system in which a +missed deadline causes the worked performed to have no value or +to result in a catastrophic effect on the integrity of the +system. + +@item heap +A data structure used to dynamically allocate +and deallocate variable sized blocks of memory. + +@item heterogeneous +A multiprocessor computer system +composed of dissimilar processors. + +@item homogeneous +A multiprocessor computer system +composed of a single type of processor. + +@item ID +An RTEMS assigned identification tag used to +access an active object. + +@item IDLE task +A special low priority task which assumes +control of the CPU when no other task is able to execute. + +@item interface +A specification of the methodology used +to connect multiple independent subsystems. + +@item internal address +The address used to access +dual-ported memory by the node which owns the memory. + +@item interrupt +A hardware facility that causes the CPU +to suspend execution, save its status, and transfer control to a +specific location. + +@item interrupt level +A mask used to by the CPU to +determine which pending interrupts should be serviced. If a +pending interrupt is below the current interrupt level, then the +CPU does not recognize that interrupt. + +@item Interrupt Service Routine +An ISR is invoked by the +CPU to process a pending interrupt. + +@item I/O +An acronym for Input/Output. + +@item ISR +An acronym for Interrupt Service Routine. + +@item kernel +In this document, this term is used as a +synonym for executive. + +@item list +A data structure which allows for dynamic +addition and removal of entries. It is not statically limited +to a particular size. + +@item little endian +A data representation scheme in which +the bytes composing a numeric value are arranged such that the +least significant byte is at the lowest address. + +@item local +An object which was created with the LOCAL +attribute and is accessible only on the node it was created and +resides upon. In a single processor configuration, all objects +are local. + +@item local operation +The manipulation of an object which +resides on the same node as the calling task. + +@item logical address +An address used by an application. +In a system without memory management, logical addresses will +equal physical addresses. + +@item loosely-coupled +A multiprocessor configuration +where shared memory is not used for communication. + +@item major number +The index of a device driver in the +Device Driver Table. + +@item manager +A group of related RTEMS' directives which +provide access and control over resources. + +@item memory pool +Used interchangeably with heap. + +@item message +A sixteen byte entity used to communicate +between tasks. Messages are sent to message queues and stored +in message buffers. + +@item message buffer +A block of memory used to store +messages. + +@item message queue +An RTEMS object used to synchronize +and communicate between tasks by transporting messages between +sending and receiving tasks. + +@item Message Queue Control Block +A data structure +associated with each message queue used by RTEMS to manage that +message queue. + +@item minor number +A numeric value passed to a device +driver, the exact usage of which is driver dependent. + +@item mode +An entry in a task's control block that is +used to determine if the task allows preemption, timeslicing, +processing of signals, and the interrupt disable level used by +the task. + +@item MPCI +An acronym for Multiprocessor Communications +Interface Layer. + +@item multiprocessing +The simultaneous execution of two +or more processes by a multiple processor computer system. + +@item multiprocessor +A computer with multiple CPUs +available for executing applications. + +@item Multiprocessor Communications Interface Layer +A set +of user-provided routines which enable the nodes in a +multiprocessor system to communicate with one another. + +@item Multiprocessor Configuration Table +The data +structure defining the characteristics of the multiprocessor +target system with which RTEMS will communicate. + +@item multitasking +The alternation of execution amongst a +group of processes on a single CPU. A scheduling algorithm is +used to determine which process executes at which time. + +@item mutual exclusion +A term used to describe the act of +preventing other tasks from accessing a resource simultaneously. + +@item nested +A term used to describe an ASR that occurs +during another ASR or an ISR that occurs during another ISR. + +@item node +A term used to reference a processor running +RTEMS in a multiprocessor system. + +@item non-existent +The state occupied by an uncreated or +deleted task. + +@item numeric coprocessor +A component used in computer +systems to enhance performance in mathematically intensive +situations. It is typically viewed as a logical extension of +the primary processor. + +@item object +In this document, this term is used to refer +collectively to tasks, timers, message queues, partitions, +regions, semaphores, ports, and rate monotonic periods. All +RTEMS objects have IDs and user-assigned names. + +@item object-oriented +A term used to describe systems +with common mechanisms for utilizing a variety of entities. +Object-oriented systems shield the application from +implementation details. + +@item operating system +The software which controls all +the computer's resources and provides the base upon which +application programs can be written. + +@item overhead +The portion of the CPUs processing power +consumed by the operating system. + +@item packet +A buffer which contains the messages passed +between nodes in a multiprocessor system. A packet is the +contents of an envelope. + +@item partition +An RTEMS object which is used to allocate +and deallocate fixed size blocks of memory from an dynamically +specified area of memory. + +@item Partition Control Block +A data structure associated +with each partition used by RTEMS to manage that partition. + +@item pending +A term used to describe a task blocked +waiting for an event, message, semaphore, or signal. + +@item periodic task +A task which must execute at regular +intervals and comply with a hard deadline. + +@item physical address +The actual hardware address of a +resource. + +@item poll +A mechanism used to determine if an event has +occurred by periodically checking for a particular status. +Typical events include arrival of data, completion of an action, +and errors. + +@item pool +A collection from which resources are +allocated. + +@item portability +A term used to describe the ease with +which software can be rehosted on another computer. + +@item posting +The act of sending an event, message, +semaphore, or signal to a task. + +@item preempt +The act of forcing a task to relinquish the +processor and dispatching to another task. + +@item priority +A mechanism used to represent the relative +importance of an element in a set of items. RTEMS uses priority +to determine which task should execute. + +@item priority inheritance +An algorithm that calls for +the lower priority task holding a resource to have its priority +increased to that of the highest priority task blocked waiting +for that resource. This avoids the problem of priority +inversion. + +@item priority inversion +A form of indefinite +postponement which occurs when a high priority tasks requests +access to shared resource currently allocated to low priority +task. The high priority task must block until the low priority +task releases the resource. + +@item processor utilization +The percentage of processor +time used by a task or a set of tasks. + +@item proxy +An RTEMS control structure used to represent, +on a remote node, a task which must block as part of a remote +operation. + +@item Proxy Control Block +A data structure associated +with each proxy used by RTEMS to manage that proxy. + +@item PTCB +An acronym for Partition Control Block. + +@item PXCB +An acronym for Proxy Control Block. + +@item quantum +The application defined unit of time in +which the processor is allocated. + +@item queue +Alternate term for message queue. + +@item QCB +An acronym for Message Queue Control Block. + +@item ready +A task occupies this state when it is +available to be given control of the CPU. + +@item real-time +A term used to describe systems which are +characterized by requiring deterministic response times to +external stimuli. The external stimuli require that the +response occur at a precise time or the response is incorrect. + +@item reentrant +A term used to describe routines which do +not modify themselves or global variables. + +@item region +An RTEMS object which is used to allocate +and deallocate variable size blocks of memory from a dynamically +specified area of memory. + +@item Region Control Block +A data structure associated +with each region used by RTEMS to manage that region. + +@item registers +Registers are locations physically +located within a component, typically used for device control or +general purpose storage. + +@item remote +Any object that does not reside on the local +node. + +@item remote operation +The manipulation of an object +which does not reside on the same node as the calling task. + +@item return code +Also known as error code or return +value. + +@item resource +A hardware or software entity to which +access must be controlled. + +@item resume +Removing a task from the suspend state. If +the task's state is ready following a call to the task_resume +directive, then the task is available for scheduling. + +@item return code +A value returned by RTEMS directives to +indicate the completion status of the directive. + +@item RNCB +An acronym for Region Control Block. + +@item round-robin +A task scheduling discipline in which +tasks of equal priority are executed in the order in which they +are made ready. + +@item RS-232 +A standard for serial communications. + +@item running +The state of a rate monotonic timer while +it is being used to delineate a period. The timer exits this +state by either expiring or being canceled. + +@item schedule +The process of choosing which task should +next enter the executing state. + +@item schedulable +A set of tasks which can be guaranteed +to meet their deadlines based upon a specific scheduling +algorithm. + +@item segments +Variable sized memory blocks allocated +from a region. + +@item semaphore +An RTEMS object which is used to +synchronize tasks and provide mutually exclusive access to +resources. + +@item Semaphore Control Block +A data structure associated +with each semaphore used by RTEMS to manage that semaphore. + +@item shared memory +Memory which is accessible by +multiple nodes in a multiprocessor system. + +@item signal +An RTEMS provided mechanism to communicate +asynchronously with a task. Upon reception of a signal, the ASR +of the receiving task will be invoked. + +@item signal set +A thirty-two bit entity which is used to +represent a task's collection of pending signals and the signals +sent to a task. + +@item SMCB +An acronym for Semaphore Control Block. + +@item soft real-time system +A real-time system in which a +missed deadline does not compromise the integrity of the system. + +@item sporadic task +A task which executes at irregular +intervals and must comply with a hard deadline. A minimum +period of time between successive iterations of the task can be +guaranteed. + +@item stack +A data structure that is managed using a Last +In First Out (LIFO) discipline. Each task has a stack +associated with it which is used to store return information +and local variables. + +@item status code +Also known as error code or return +value. + +@item suspend +A term used to describe a task that is not +competing for the CPU because it has had a task_suspend +directive. + +@item synchronous +Related in order or timing to other +occurrences in the system. + +@item system call +In this document, this is used as an +alternate term for directive. + +@item target +The system on which the application will +ultimately execute. + +@item task +A logically complete thread of execution. The +CPU is allocated among the ready tasks. + +@item Task Control Block +A data structure associated with +each task used by RTEMS to manage that task. + +@item task switch +Alternate terminology for context +switch. Taking control of the processor from one task and given +to another. + +@item TCB +An acronym for Task Control Block. + +@item tick +The basic unit of time used by RTEMS. It is a +user-configurable number of microseconds. The current tick +expires when the clock_tick directive is invoked. + +@item tightly-coupled +A multiprocessor configuration +system which communicates via shared memory. + +@item timeout +An argument provided to a number of +directives which determines the maximum length of time an +application task is willing to wait to acquire the resource if +it is not immediately available. + +@item timer +An RTEMS object used to invoke subprograms at +a later time. + +@item Timer Control Block +A data structure associated +with each timer used by RTEMS to manage that timer. + +@item timeslicing +A task scheduling discipline in which +tasks of equal priority are executed for a specific period of +time before being preempted by another task. + +@item timeslice +The application defined unit of time in +which the processor is allocated. + +@item TMCB +An acronym for Timer Control Block. + +@item transient overload +A temporary rise in system +activity which may cause deadlines to be missed. Rate Monotonic +Scheduling can be used to determine if all deadlines will be met +under transient overload. + +@item user extensions +Software routines provided by the +application to enhance the functionality of RTEMS. + +@item User Extension Table +A table which contains the +entry points for each user extensions. + +@item User Initialization Tasks Table +A table which +contains the information needed to create and start each of the +user initialization tasks. + +@item user-provided +Alternate term for user-supplied. +This term is used to designate any software routines which must +be written by the application designer. + +@item user-supplied +Alternate term for user-provided. +This term is used to designate any software routines which must +be written by the application designer. + +@item vector +Memory pointers used by the processor to +fetch the address of routines which will handle various +exceptions and interrupts. + +@item wait queue +The list of tasks blocked pending the +release of a particular resource. Message queues, regions, and +semaphores have a wait queue associated with them. + +@item yield +When a task voluntarily releases control of the processor. + +@end table + -- cgit v1.2.3