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26-516: Open Firmware allows a system to load platform -independent drivers directly from a PCI device, improving compatibility. Open Firmware may be accessed through its command line interface , which uses the Forth programming language . Open Firmware was described by IEEE standard as IEEE 1275-1994 . This standard was not reaffirmed by the Open Firmware Working Group (OFWG) since 1998, and

52-402: A shell pipeline , the output of the first process needs to pass to the second one, and so on. Another example is a task that has been decomposed into cooperating but partially independent processes which can run simultaneously (i.e., using concurrency, or true parallelism – the latter model is a particular case of concurrent execution and is feasible whenever multiple CPU cores are available for

78-740: A virtual memory system, where regions of a process's memory may be really on disk and not in main memory at any time. Even portions of active processes/tasks (executing programs) are eligible for swapping to disk, if the portions have not been used recently. Not all parts of an executing program and its data have to be in physical memory for the associated process to be active. An operating system kernel that allows multitasking needs processes to have certain states . Names for these states are not standardised, but they have similar functionality. When processes need to communicate with each other they must share parts of their address spaces or use other forms of inter-process communication (IPC). For instance in

104-501: A web browser . As long as it is a required component for the program code to execute, it is part of the computing platform. Platforms may also include: Some architectures have multiple layers, with each layer acting as a platform for the one above it. In general, a component only has to be adapted to the layer immediately beneath it. For instance, a Java program has to be written to use the Java virtual machine (JVM) and associated libraries as

130-510: A computer video game , the most relevant layer is the operating system, so it can be called a platform itself (hence the term cross-platform for software that can be executed on multiple OSes, in this context). In a multi-computer system, such as in the case of offloading processing, it would encompass both the host computer's hardware , operating system (OS), and runtime libraries along with other computers utilized for processing that are accessed via application programming interfaces or

156-640: A platform but does not have to be adapted to run on the Windows, Linux or Macintosh OS platforms. However, the JVM, the layer beneath the application, does have to be built separately for each OS. Process (computing) In computing , a process is the instance of a computer program that is being executed by one or many threads . There are many different process models, some of which are light weight, but almost all processes (even entire virtual machines ) are rooted in an operating system (OS) process which comprises

182-457: A single process at a time. However, multitasking allows each processor to switch between tasks that are being executed without having to wait for each task to finish ( preemption ). Depending on the operating system implementation, switches could be performed when tasks initiate and wait for completion of input/output operations, when a task voluntarily yields the CPU, on hardware interrupts , and when

208-403: A time: it is impossible to run more programs at the same time. A program might need some resource , such as an input device, which has a large delay, or a program might start some slow operation, such as sending output to a printer. This would lead to processor being "idle" (unused). To keep the processor busy at all times, the execution of such a program is halted and the operating system switches

234-416: Is "something that takes up time", as opposed to "memory", which is "something that takes up space". The above description applies to both processes managed by an operating system, and processes as defined by process calculi . If a process requests something for which it must wait, it will be blocked. When the process is in the blocked state , it is eligible for swapping to disk, but this is transparent in

260-543: Is also very compact, so that a disk driver may require only one or two kilobytes. Therefore, many of the same I/O cards can be used on Sun systems and Macintoshes that used Open Firmware. FCode implements ANS Forth and a subset of the Open Firmware library. Being based upon an interactive programming language, Open Firmware can be used to efficiently test and bring up new hardware. It allows drivers to be written and tested interactively. Operational video and mouse drivers are

286-465: Is available from the OpenBIOS project. Sun's implementation is available under a BSD license . Platform (computing) A computing platform , digital platform , or software platform is the infrastructure on which software is executed. While the individual components of a computing platform may be obfuscated under layers of abstraction , the summation of the required components comprise

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312-465: Is called concurrency . For security and reliability, most modern operating systems prevent direct communication between independent processes, providing strictly mediated and controlled inter-process communication. In general, a computer system process consists of (or is said to own ) the following resources: The operating system holds most of this information about active processes in data structures called process control blocks . Any subset of

338-403: Is said to own resources, of which an image of its program (in memory) is one such resource. However, in multiprocessing systems many processes may run off of, or share, the same reentrant program at the same location in memory, but each process is said to own its own image of the program. Processes are often called "tasks" in embedded operating systems. The sense of "process" (or task)

364-399: Is the execution of those instructions after being loaded from the disk into memory. Several processes may be associated with the same program; for example, opening up several instances of the same program often results in more than one process being executed. Multitasking is a method to allow multiple processes to share processors (CPUs) and other system resources. Each CPU (core) executes

390-577: The alternative solution of performing a blind probe of the IC bus, as has to be done by software like lm_sensors on generic hardware, is known to result in serious hardware issues under certain circumstances. Open Firmware Forth Code may be compiled into FCode, a bytecode which is independent of instruction set architecture . A PCI card may include a program, compiled to FCode, which runs on any Open Firmware system. In this way, it can provide boot-time diagnostics , configuration code, and device drivers . FCode

416-451: The appearance of many processes executing simultaneously (that is, in parallel ), though in fact only one process can be executing at any one time on a single CPU (unless the CPU has multiple cores, then multithreading or other similar technologies can be used). It is usual to associate a single process with a main program, and child processes with any spin-off, parallel processes, which behave like asynchronous subroutines. A process

442-427: The computing platform . Sometimes, the most relevant layer for a specific software is called a computing platform in itself to facilitate the communication, referring to the whole using only one of its attributes – i.e. using a metonymy . For example, in a single computer system, this would be the computer's architecture , operating system (OS), and runtime libraries . In the case of an application program or

468-575: The only prerequisite for a graphical interface suitable for end-user diagnostics. Apple shipped such a diagnostic "operating system" in many Power Macintoshes. Sun also shipped an FCode-based diagnostic tool suite called OpenBoot Diagnostics (OBDiag) used by customer service support and hardware manufacturing teams Several commercial implementations of Open Firmware have been released to the Open Source community since 2006, including Sun OpenBoot, Firmworks OpenFirmware and Codegen SmartFirmware. The source code

494-743: The operating system scheduler decides that a process has expired its fair share of CPU time (e.g, by the Completely Fair Scheduler of the Linux kernel ). A common form of multitasking is provided by CPU's time-sharing that is a method for interleaving the execution of users' processes and threads, and even of independent kernel tasks – although the latter feature is feasible only in preemptive kernels such as Linux . Preemption has an important side effect for interactive processes that are given higher priority with respect to CPU bound processes, therefore users are immediately assigned computing resources at

520-618: The processes that are ready to run). It is even possible for two or more processes to be running on different machines that may run different operating system (OS), therefore some mechanisms for communication and synchronization (called communications protocols for distributed computing) are needed (e.g., the Message Passing Interface {MPI}). By the early 1960s, computer control software had evolved from monitor control software , for example IBSYS , to executive control software . Over time, computers got faster while computer time

546-400: The processor to run another program. To the user, it will appear that the programs run at the same time (hence the term "parallel"). Shortly thereafter, the notion of a "program" was expanded to the notion of an "executing program and its context". The concept of a process was born, which also became necessary with the invention of re-entrant code . Threads came somewhat later. However, with

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572-444: The program code, assigned system resources, physical and logical access permissions, and data structures to initiate, control and coordinate execution activity. Depending on the OS, a process may be made up of multiple threads of execution that execute instructions concurrently . While a computer program is a passive collection of instructions typically stored in a file on disk, a process

598-607: The resources, typically at least the processor state, may be associated with each of the process' threads in operating systems that support threads or child processes. The operating system keeps its processes separate and allocates the resources they need, so that they are less likely to interfere with each other and cause system failures (e.g., deadlock or thrashing ). The operating system may also provide mechanisms for inter-process communication to enable processes to interact in safe and predictable ways. A multitasking operating system may just switch between processes to give

624-428: The simple pressing of a key or when moving a mouse. Furthermore, applications like video and music reproduction are given some kind of real-time priority, preempting any other lower priority process. In time-sharing systems, context switches are performed rapidly, which makes it seem like multiple processes are being executed simultaneously on the same processor. This seemingly-simultaneous execution of multiple processes

650-626: Was still neither cheap nor fully utilized; such an environment made multiprogramming possible and necessary. Multiprogramming means that several programs run concurrently . At first, more than one program ran on a single processor, as a result of underlying uniprocessor computer architecture, and they shared scarce and limited hardware resources; consequently, the concurrency was of a serial nature. On later systems with multiple processors , multiple programs may run concurrently in parallel . Programs consist of sequences of instructions for processors. A single processor can run only one instruction at

676-514: Was therefore officially withdrawn by IEEE in May 2005. Open Firmware defines a standard way to describe the hardware configuration of a system, called the device tree . This helps the operating system to better understand the configuration of the host computer, relying less on user configuration and hardware polling. For example, Open Firmware is essential for reliably identifying slave IC devices like temperature sensors for hardware monitoring , whereas

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