Exec (Amiga)

Exec is the multitasking kernel of AmigaOS. It enabled pre-emptive multitasking in as little as 256 KB of memory (as supplied with the first Amiga 1000s). Exec provided functionality for multitasking, memory allocation, interrupt handling and handling of dynamic shared libraries.

It acts as a scheduler for tasks running on the system, providing pre-emptive multitasking with prioritized round-robin scheduling. Exec also provides access to other libraries and high-level inter-process communication via message passing. Other comparable microkernels have had performance problems because of the need to copy messages between address spaces. Since the Amiga has only one address space, Exec message passing is quite efficient. The only fixed memory address in the Amiga software (address 4) is a pointer to exec.library, which can then be used to access other libraries. Exec was designed and implemented by Carl Sassenrath.

Unlike newer modern operating systems, the exec kernel does not run "privileged". Contemporary operating systems for the 68000 such as Atari TOS and SunOS used trap instructions for invoking kernel functions. This made the kernel functions run in the 68000's supervisor mode, while user software ran in the unprivileged user mode. By contrast, exec function calls are made with the library jump table, and the kernel code normally executes in user mode. Whenever supervisor mode is needed, either by the kernel or user programs, the library functions Supervisor() or SuperState() are used.

Exec

Exec or EXEC may refer to:

Computing

See also

Exec (errand service)

Exec was a company based in San Francisco, USA, that provided companies and individuals access to on-demand personal assistants (for delivery, furniture assembly, research, etc.) and cleaning services. Started by Justin Kan, founder of Justin.tv, in February 2012 with co-founders Daniel Kan, his brother, and Amir Ghazvinian, Exec was backed by Y Combinator and other prominent investors. The company was acquired by Handy (company) in January 2014.

History

Exec received $3.3 million in seed funding. In September 2013, Exec shut down its errand service to focus on its cleaning service . In January 2014, Handybook, a company founded by Oisin Hanrahan, Umang Dua, Ignacio Leonhardt, and Weina Scott in 2012 announced that it had acquired Exec.

Business method

Exec’s errand service had no auction process, and was not an open marketplace. The jobs were dispatched to nearby individuals with the appropriate skills and good ratings, at a flat rate of $38 an hour .

Reception

Exec was nominated for Techcrunch's 2012 TechCrunchie Award for Fastest Rising Startup. Exec’s cleaning service garnered positive reviews from web publications such as TechCrunch praising their professionalism and efficiency. Exec also received positive coverage by other publications such as The New York Times, Huffington Post, Forbes, Inc., and Business Insider.

OS 2200

OS 2200 is the operating system for the Unisys ClearPath Dorado family of mainframe systems. The operating system kernel of OS 2200 is a lineal descendant of Exec 8 for the UNIVAC 1108. Documentation and other information on current and past Unisys systems can be found on the Unisys public support website.

See Unisys 2200 Series system architecture for a description of the machine architecture and its relationship to the OS 2200 operating system.

History

There were earlier 1100 systems going back to the 1101 in 1951, but the 1108 was the first 1100 Series computer designed for efficient support of multiprogramming and multiprocessing. Along with this new hardware came the operating system Exec 8 (Executive System for the 1108).

The UNIVAC 1108 computer was announced in 1964 and delivered in late 1965. The first 1108 computers used Exec I and Exec II, which had been developed for the UNIVAC 1107. However, UNIVAC planned to offer symmetric multiprocessor versions of the 1108 with up to 4 processors and the earlier operating systems (really basic monitor programs) weren’t designed for that, even though they supported limited multiprogramming.

Amiga

The Amiga is a family of personal computers sold by Commodore in the 1980s and 1990s. Based on the Motorola 68000 family of microprocessors, the machine has a custom chipset with graphics and sound capabilities that were unprecedented for the price, and a pre-emptive multitasking operating system called AmigaOS. The Amiga provided a significant upgrade from earlier 8-bit home computers, including Commodore's own C64.

The Amiga 1000 was officially released in July 1985, but a series of production problems meant it did not become widely available until early 1986. The best selling model, the Amiga 500, was introduced in 1987 and became one of the leading home computers of the late 1980s and early 1990s with four to six million sold. The A3000, introduced in 1990, started the second generation of Amiga systems, followed by the A500+ and the A600. Finally, as the third generation, the A1200 and the A4000 were released in 1992. The platform became particularly popular for gaming and programming demos. It also found a prominent role in the desktop video, video production, and show control business, leading to affordable video editing systems such as the Video Toaster. The Amiga's native ability to simultaneously play back multiple digital sound samples made it a popular platform for early "tracker" music software. The relatively powerful processor and ability to access several megabytes of memory led to the development of several 3D rendering packages, including LightWave 3D and Aladdin 4D.

Amiga (disambiguation)

Amiga (the Portuguese and Spanish word for "friend" in the feminine, i.e. "female friend") may refer to:

Businesses and products

Amiga 500 Plus

The Commodore Amiga 500 Plus (often A500 Plus or simply A500+) is an enhanced version of the original Amiga 500 computer. It was notable for introducing new versions of Kickstart and Workbench, and for some minor improvements in the custom chips, known as the Enhanced Chip Set (or ECS).

Introduction

The A500+ was released in several markets (including many European countries), but was never sold officially in the U.S.

Although officially introduced in 1992, some Amiga 500 Plus units had already been sold (masquerading as Amiga 500 models, and with no prior announcement) during late 1991. It has been speculated that Commodore had already sold out the remaining stocks of Amiga 500s, before the run up to the profitable Christmas sales period. In order to make enough A500s before Christmas, Commodore used stocks of the new 8A revision motherboards destined for the A500+. Many users were unaware that they were purchasing anything other than a standard Amiga 500. Although the Amiga 500+ was an improvement to the Amiga 500, it was minor. It was discontinued and replaced by the Amiga 600 in summer 1992, making it the shortest lived Amiga model.