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- atomic
- Of or relating to atoms. :-).
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- BIOS/ROM Monitor extension signature
- A certain sequence of bytes indicating to the BIOS or ROM Monitor that the device is to be considered an "extension" to the BIOS or ROM Monitor -- control is to be transferred to the device by the BIOS or ROM Monitor, with the expectation that the device will perform additional initializations.
On the x86 architecture, the two bytes 0x55 and 0xAA must be present (in that order) as the first two bytes in the device, with control being transferred to offset 0x0003.
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- budget
- In sporadic scheduling, the amount of time a thread is permitted to execute at its normal priority before being dropped to its low priority.
- buildfile
- A text file containing instructions for mkifs specifying the contents and other details of an image, or for mkefs specifying the contents and other details of an embedded filesystem image.
- canonical mode
- Also called edited mode or "cooked" mode. In this mode the character device library performs line-editing operations on each received character. Only when a line is "completely entered" -- typically when a carriage return (CR) is received -- will the line of data be made available to application processes. Contrast raw mode.
- channel
- A kernel object used with message passing.()).
- CIFS
- Common Internet File System (aka SMB) -- a protocol that allows a client workstation to perform transparent file access over a network to a Windows..
- cooked mode
- See canonical mode.
- core dump
- A file describing the state of a process that terminated abnormally.
- critical section
- A code passage that must be executed "serially" (i.e. by only one thread at a time). The simplest from of critical section enforcement is via a mutex.
- are standard processes that can be started and stopped dynamically. As a result, adding device drivers doesn't affect any other part of the OS -- drivers can be developed and debugged like any other application. Also, device drivers are in their own protected address space, so a bug in a device driver won't cause the entire OS to shut down.
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- EPROM
- Erasable Programmable Read-Only Memory -- a memory technology that allows the device to be programmed (typically with higher-than-operating voltages, e.g. 12V), with the characteristic that any bit (or bits) may be individually programmed from a 1 state to a 0 state. To change a bit from a 0 state into a 1 state can only be accomplished flash and RAM.
- event
- A notification scheme used to inform a thread that a particular condition has occurred. Events can be signals or pulses in the general case; they can also be unblocking events or interrupt events in the case of kernel timeouts and interrupt service routines. An event is delivered by a thread, a timer, the kernel, or an interrupt service routine when appropriate to the requestor of the event.
- offers several forms of IPC, most notably native messaging (synchronous, client/server relationship), POSIX message queues and pipes (asynchronous), as well as signals.
- IPL
- Initial Program Loader -- the software component that either takes control at the processor's reset vector (e.g. location 0xFFFFFFF0 on the x86), or is a BIOS extension. This component is responsible for setting up the machine into a usable state, such that the startup program can then perform further initializations. The IPL is written in assembler and C. See also BIOS extension signature and startup code.
- IRQ
- Interrupt Request -- a hardware request line asserted by a peripheral to indicate that it requires servicing by software. The IRQ is handled by the PIC, which then interrupts the processor, usually causing the processor to execute an Interrupt Service Routine (ISR).
- ISR
- Interrupt Service Routine -- a routine responsible for servicing hardware (e.g. reading and/or writing some device ports), for updating some data structures shared between the ISR and the thread(s) running in the application, and for signalling the thread that some kind of event has occurred.
- kernel
- See microkernel.
- level-sensitive
- One of two ways in which a PIC (Programmable Interrupt Controller) can be programmed to respond to interrupts. If the PIC is operating in level-sensitive mode, the IRQ is considered active whenever the corresponding hardware line is active. Contrast edge-sensitive.
- linearly mapped
- A term indicating that a certain memory component is entirely addressable by the processor. Contrast bank-switched.
- A parcel of bytes passed from one process to another. The OS attaches no special meaning to the content of network, the process by which the Qnet network manager converts an FQNN to a list of destination addresses that the transport layer knows how to get to.
- name resolver
- Program code that attempts to convert an FQNN to a destination address.
- NDP
- Node Discovery Protocol -- proprietary QNX Software Systems protocol for broadcasting name resolution requests on a QNX Neutrino LAN.
- network directory
- A directory in the pathname space that's implemented by the Qnet network manager.
- Neutrino
- Name of an OS developed by QNX Software Systems.
- NFS
- Network FileSystem -- a TCP/IP application that.
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- preemption
- The act of suspending the execution of one thread and starting (or resuming) another. The suspended thread is said to have been "preempted" by the new thread. Whenever a lower-priority thread is actively consuming the CPU, and a higher-priority thread becomes READY, the lower-priority thread is immediately preempted by the higher-priority thread.
- prefix tree
- The internal representation used by the Process Manager to store the pathname table.
- priority inheritance
- The characteristic of a thread that causes its priority to be raised or lowered to that of the thread that sent it a message. Also used with mutexes. Priority inheritance is a method used to prevent priority inversion.
- priority inversion
- A condition that can occur when a low-priority thread consumes CPU at a higher priority than it should. This can be caused by not supporting priority inheritance, such that when the lower-priority thread sends a message to a higher-priority thread, the higher-priority thread consumes CPU on behalf of the lower-priority thread. This is solved by having the higher-priority thread inherit the priority of the thread on whose behalf it's working.
- process
- A nonschedulable entity, which defines the address space and a few data areas. A process must have at least one thread running in it -- this thread is then called the first thread.
- process group
- A collection of processes that permits the signalling of related processes. Each process in the system is a member of a process group identified by a process group ID. A newly created process joins the process group of its creator.
- process group ID
- The unique identifier representing a process group during its lifetime. A process group ID is a positive integer. The system may reuse a process group ID after the process group dies.
- process group leader
- A process whose ID is the same as its process group ID.
- process ID (PID)
- The unique identifier representing a process. A PID is a positive integer. The system may reuse a process ID after the process dies, provided no existing process group has the same ID. Only the Process Manager can have a process ID of 1.
- pty
- Pseudo-TTY -- a character-based device that has two "ends": a master end and a slave end. Data written to the master end shows up on the slave end, and vice versa.ROM.
- raw mode
- In raw input mode, the character device library performs no editing on received characters. This reduces the processing done on each character to a minimum and provides the highest performance interface for reading data. Also, raw mode is used with devices that typically generate binary data -- you don't want any translations of the raw binary stream between the device and the application. Contrast canonical mode.
- replenishment
- In sporadic scheduling, the period of time during which a thread is allowed to consume its execution budget.
- reset vector
- The address at which the processor begins executing instructions after the processor's reset line has been activated. On the x86, for example, this is the address 0xFFFFFFF0.
- resource manager
- A user-level server program that accepts messages from other programs and, optionally, communicates with hardware. QNX Neutrino resource managers are responsible for presenting an interface to various types of devices, whether actual (e.g. serial ports, parallel ports, network cards, disk drives) or virtual (e.g. /dev/null, a network filesystem, and pseudo-ttys)..
- RMA
- Rate Monotonic Analysis -- a set of methods used to specify, analyze, and predict the timing behavior of realtime systems.
- round robin
- Scheduling algorithm whereby a thread is given a certain period of time to run. Should the thread consume CPU for the entire period of its timeslice, the thread will be placed at the end of the ready queue for its priority, and the next available thread will be made READY. If a thread is the only thread READY at its priority level, it will be able to consume CPU again immediately. See also adaptive, FIFO, and sporadic.
- runmask
- A bitmask that indicates which processors a thread can run on. Contrast inherit mask.
- runtime loading
- The process whereby a program decides while it's actually running that it wishes to load a particular function from a library. Contrast static linking.
- scheduling latency
- The amount of time that elapses between the point when one thread makes another thread READY and when the other thread actually gets some CPU time. Note that this latency is almost always at the control of the system designer.
Also designated as "Tsl". Contrast interrupt latency.
- session
- A collection of process groups established for job control purposes. Each process group is a member of a session. A process belongs to the session that its process group belongs to. A newly created process joins the session of its creator. A process can alter its session membership via setsid(). A session can contain multiple process groups.
- session leader
- A process whose death causes all processes within its process group to receive a SIGHUP signal.
-. A thread is a flow of execution; it exists within the context of a process.
- timer
- A kernel object used in conjunction with time-based functions. A timer is created via timer_create() and armed via timer_settime(). A timer can then deliver an event, either periodically or on a one-shot basis.
- timeslice
- A period of time assigned to a round-robin or adaptive scheduled thread. This period of time is small (on the order of tens of milliseconds); the actual value shouldn't be relied upon by any program (it's considered bad design).