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A software quality that is a measure of how easy the system can be evolved to accommodate new features, or changed to repair errors.
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Memory that is directly addressable by the CPU
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An input/output scheme where reading or writing involves executing a load or store instruction on a pseudomemory address mapped to the device
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An intertask communication device consisting of a memory location and two operations – post and pend – that can be performed on it
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A device used to route multiple lines onto fewer lines
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The smallest portion of the operating system that provides for task scheduling, dispatching, and inertia communication
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A device that must be reset periodically or a discrete signal is issued
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The interval between when data are requested from the memory cell and when they are actually vailable
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Operation on a semaphore that essentially locks the resource protected by the semaphore, or prevents the requesting task from proceeding if the resource is already locked
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A systematic and precise,step-by-step procedure for solving a certain kind of problem oraccomplishing a task,for instance converting a particular kind of input data to a particular kind of output data
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A fixed time quantum used to limit execution time in round-robin systems.
Memory in which the contents will be lost if power is removed
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An address or value that is passed to a procedure or function call, as a way of communicating cleanly across procedure/function boundaries
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An operating system where more than one processor is available to provide for simultaneity.
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A predefined subprogram that is executed when an interrupt occurs. The handler can perform input or output, save data, update pointers, or notify other processes of the event.
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A computer system that has more than one internal processor capable of operating collectively on a computation. Normally associated with those systems
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An input to a processor that signals the occurrence of an asynchronous event. The processor’s response to an interrupt is to save the current machine state and execute a predefined subprogram.
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An operating system that provides sufficient functionality to allow multiple programs to run on a single processor so that the illusion of simultaneity is created.
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A real-time system in which missing even one deadline results in system failure
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A collection of data associated with a task including context, process code (or a pointer to it), and other information.
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Software that translates assembly language to machine code
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In the task-control block model, those tasks that are waiting on a particular resource, and thus are not ready
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Noninterrupt-driven processes in foreground/background systems
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A group of instructions written to perform a task, independent of a main program and can be accessed by a program or another subroutine to perform the task.
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A testing methodology where only the inputs and outputs of the unit are considered. How the outputs are generated inside the unit is ignored
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Memory whose contents are preserved upon removing power
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Any variables that is within the scope of all modules of the software system.
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A set of programs that manages the operations of a computer. It oversees the interaction between the hardware and the software and provides a set of services to system users
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A software run-time system component that periodically scans dynamically allocated storage and reclaims allocated storage that is no longer in use.
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Operation of removing data from a mailbox. If data are not available, the process performing the pend suspends itself until the data become available.
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An object or a set of objects that can no longer be accessed, typically because all pointers that direct accesses to the object or set have been eliminated.
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A condition that occurs when a task is not being serviced frequently enough.
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The condition experienced by tasks that are waiting for the occurrence of an event.
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A first-in, last-out data structure.
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A temporary data storage area used to interface between, for example, a fast device and a slower process servicing that device.
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A task driven by an interrupt that occurs periodically
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A program that translates a high-level language program into an executable machine instruction program or other lower-level form such as assembly language.
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A real-time system in which failure to meet deadlines results in performance degradation but not necessarily failure.
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The minimum information that is needed in order to save a currently executing task so that it can be resumed.
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A special variable type used for protecting critical regions.
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The process of saving and restoring sufficient information for a real-time task so that it can be resumed after being interrupted.
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A measure of the software’s capability of meeting certain functional constraints such as timing or output precision.
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A collection of interrupt driven or real-time processes.
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A real-time system in which a single and repetitive test instruction is used to test a flag that indicates that some event has occurred.
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Code used to process exceptions.
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A quality in which the software can easily run in different environments.
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Error or other special condition that arises during program execution
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Operation that places data in a mailbox
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When the next states and outputs of the system are known for each set of inputs that trigger events.
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A series of diagnostic tests performed by a machine (such as the personal computer) when it powers on.
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Any occurrence that results in a change in the state of a system.
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In certain programming languages, a pseudo-op that allows assembly code to be placed in line with the high-order language code.
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A computing machine contained in a device whose purpose is not to be a computer. For example, the computers in automobiles and household appliances are embedded computers
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A condition that occurs when a higher-priority task interrupts a lower-priority task
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A technique using two buffers where one is filled while the data in the other is being used
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A system that uses preemption schemes instead of round-robin or first-come, first-served scheduling
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In the task-control block model, a state that is best described as a TCB belonging to a task that is unavailable to the operating system
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A condition that occurs because a noncritical task with a high execution rate will have a higher priority than a critical task with a low execution rate
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The part of the kernel that performs the necessary bookkeeping to start a task.
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An area of memory containing information about the context of an executing program. Although the process control block is primarily a software mechanism
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A computer program that can take an executable image and convert it back into assembly code.
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A scheme in which access to the computer’s memory is afforded to other devices in the system without the intervention of the CPU.
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Transferring data to or from a peripheral device by running a program that executes individual computer instruction or commands to control the transfer.
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A system where for each possible state, and each set of inputs, a unique set of outputs and next state of the system can be determined.
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In the task-control block model, the state of those tasks that are ready to run, but are not running.
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The value or status that is assumed unless otherwise specified
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Refers to systems whose correctness depends not only on outputs but the timeliness of those outputs. Failure to meet one or more of the deadlines can result in system failure
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A program that allows interactive analysis of a running program, by allowing the user to pause execution of the running program and examine its variables and path of execution at any point.
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The time between the presentation of a set of inputs to a software system and the appearance of all the associated outputs.
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A catastrophic situation that can arise when tasks are competing for the same set of two or more serially reusable resources
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A first-in, first-out list in which simultaneous input and output to the list is achieved by keeping head and tail pointers. Data are loaded at the tail and read from the head.
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Code that interacts with a serially reusable resource.
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A scheme in which two or more processes are divided into states or phases, determined by a finite state automaton. Calls to a central dispatcher are made after each phase is complete.
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A system in which several processes are executed sequentially to completion, often in conjunction with a cyclic executive
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A system in which each executable task is assigned a fixed time quantum called a time slice in which to execute. A clock is used to initiate an interrupt at a rate corresponding to the time slice.
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The part of the kernel that determines which task will run
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Computer devices such as hard disks, floppy disks, tapes, and so forth, that are not part of the physical address space of the CPU.
