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MY'STORY

The MOVE Fire

This is a personal recollection on the Move fire on May 13, 1985 Philadelphia police fired thousands of rounds at the MOVE house, city officials approved dropping an explosive device on the roof, the resulting fire was allowed to burn, 11 people—including five children—died, and 61 homes were destroyed. Philadelphia City Council later called it a “brutal attack carried out by the City of Philadelphia on its own citizens” and acknowledged that no individual faced criminal consequences for the bombing. One timeline correction worth preserving for the BHP record: the major previous MOVE-police confrontation was August 8, 1978, about seven years before the bombing, not a year or two earlier. Officer James Ramp was killed, other police and firefighters were wounded, nine MOVE members were later convicted, and television cameras recorded police beating Delbert Africa during his arrest. The 1985 MOVE Commission later specifically criticized city planners for failing to adequately use lessons from that 1978 confrontation. And that actually strengthens the point you’re making: 1985 did not happen without precedent or institutional memory. There had already been a deadly confrontation with MOVE, years of conflict, negotiations and police involvement before Osage Avenue.

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BLACK FACTS
The Truths They Never Taught You...

Shirley Chisholm — Unbought and Unbossed

In 1968 Shirley Chisholm became the first Black woman elected to the United States Congress. In 1972 she launched a campaign for the Democratic presidential nomination, breaking another political barrier.

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Wikipedia

Multi-Environment Real-Time

Not to be confused with Penn MERT.
Multi-Environment Real-Time
DeveloperBell Labs[1]
Written inC[2]
OS familyUnix-like
Working stateUNIX-RTR/3B21D version still in use.
Marketing targetReal-time computing applications
Available inEnglish
Supported platformsPDP-11,[1] 3B20D, 3B21D
Kernel typeMicrokernel[1] RTOS

Multi-Environment Real-Time (MERT), later renamed UNIX Real-Time (UNIX-RT),[3] is a hybrid time-sharing and real-time operating system developed in the 1970s at Bell Labs for use in embedded minicomputers (especially PDP-11s). A version named Duplex Multi Environment Real Time (DMERT) was the operating system for the AT&T 3B20D telephone switching minicomputer, designed for high availability;[4][5][6] DMERT was later renamed Unix RTR (Real-Time Reliable).[6]

A generalization of Bell Labs' time-sharing operating system Unix,[7] MERT featured a redesigned, modular kernel that was able to run Unix programs and privileged real-time computing processes. These processes' data structures were isolated from other processes with message passing being the preferred form of interprocess communication (IPC), although shared memory was also implemented. MERT also had a custom file system with special support for large, contiguous, statically sized files, as used in real-time database applications. The design of MERT was influenced by Dijkstra's THE, Hansen's Monitor, and IBM's CP-67.[2]

The MERT operating system was a four-layer design, in decreasing order of protection:[2]

  • Kernel: resource allocation of memory, CPU time and interrupts
  • Kernel-mode processes including input/output (I/O) device drivers, file manager, swap manager, root process that connects the file manager to the disk (usually combined with the swap manager)
  • Operating system supervisor
  • User processes

The standard supervisor was MERT/UNIX, a Unix emulator with an extended system call interface and shell that enabled the use of MERT's custom IPC mechanisms, although an RSX-11 emulator also existed.[2]

References

[edit]
  1. ^ a b c Bayer, D. L.; Lycklama, H. (1975). MERT: a multi-environment real-time operating system. Fifth ACM Symposium on Operating Systems Principles. Austin, Texas. doi:10.1145/800213.806519. Retrieved 2008-08-18.
  2. ^ a b c d Lycklama, H.; Bayer, D. L. (July–August 1978). "The MERT Operating System". Bell System Technical Journal. 57 (6): 2049–2086. doi:10.1002/j.1538-7305.1978.tb02142.x. S2CID 8711402.
  3. ^ Bodenstab, D. E.; Houghton, T. F.; Kelleman, K. A.; Ronkin, G.; Schan, E. P. (1984). "UNIX Operating System Porting Experiences". AT&T Bell Laboratories Technical Journal. 63 (8): 1769–1790. doi:10.1002/j.1538-7305.1984.tb00064.x. S2CID 35326182.
  4. ^ Kane, J. R.; Anderson, R. E.; McCabe, P. S. (January 1983). "The 3B20D Processor & DMERT Operating System: Overview, Architecture, and Performance of DMERT". Bell System Technical Journal. 62 (1): 291–301. doi:10.1002/j.1538-7305.1983.tb04396.x. S2CID 31828139.
  5. ^ Grzelakowski, M. E.; Campbell, J. H.; Dubman, M. R. (January 1983). "The 3B20D Processor & DMERT Operating System: DMERT Operating System". Bell System Technical Journal. 62 (1): 303–322. doi:10.1002/j.1538-7305.1983.tb04397.x. S2CID 12901173.
  6. ^ a b Wallace, John J.; Barnes, Walter W. (August 1984). "Designing for Ultrahigh Availability: The Unix RTR Operating System" (PDF). IEEE Computer. 17 (8). IEEE: 31–39. doi:10.1109/MC.1984.1659215. S2CID 17689432.
  7. ^ Ritchie, Dennis M. (1977). The Unix Time-sharing System: A retrospective. Tenth Hawaii International Conference on the System Sciences. Archived from the original on 5 February 2015.

Source: Wikipedia. Article content is retrieved live through the MediaWiki API.

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Wikipedia

Multi-Environment Real-Time

Multi-Environment Real-Time (MERT), later renamed UNIX Real-Time (UNIX-RT), is a hybrid time-sharing and real-time operating system developed in the 1970s at Bell Labs for use in embedded minicomputers (especially PDP-11s). A version named Duplex Multi Environment Real Time (DMERT) was the operating system for the AT&T 3B20D telephone switching minicomputer, designed for high availability; DMERT was later renamed Unix RTR (Real-Time Reliable). A generalization of Bell Labs' time-sharing operating system Unix, MERT featured a redesigned, modular kernel that was able to run Unix programs and privileged real-time computing processes. These processes' data structures were isolated from other processes with message passing being the preferred form of interprocess communication (IPC), although shared memory was also implemented. MERT also had a custom file system with special support for large, contiguous, statically sized files, as used in real-time database applications. The design of MERT was influenced by Dijkstra's THE, Hansen's Monitor, and IBM's CP-67. The MERT operating system was a four-layer design, in decreasing order of protection: Kernel: resource allocation of memory, CPU time and interrupts Kernel-mode processes including input/output (I/O) device drivers, file manager, swap manager, root process that connects the file manager to the disk (usually combined with the swap manager) Operating system supervisor User processes The standard supervisor was MERT/UNIX, a Unix emulator with an extended system call interface and shell that enabled the use of MERT's custom IPC mechanisms, although an RSX-11 emulator also existed.

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Wikipedia

Bourne shell

The Bourne shell (sh) is a shell command-line interpreter for computer operating systems. It first appeared on Version 7 Unix, as its default shell. Unix-like systems continue to have /bin/sh—which will be the Bourne shell, or a symbolic link or hard link to a compatible shell—even when other shells are used by most users. The Bourne shell was once standard on all branded Unix systems, although historically BSD-based systems had many scripts written in csh. As the basis of POSIX sh syntax, Bourne shell scripts can typically be run with Bash or dash on Linux or other Unix-like systems; Bash itself is a free clone of Bourne.

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Wikipedia

3B series computers

The 3B series computers are a line of minicomputers made between the late 1970s and 1993 by AT&T Computer Systems' Western Electric subsidiary, for use with the company's UNIX operating system. The line primarily consists of the models 3B20, 3B5, 3B15, 3B2, and 3B4000. The series is notable for controlling a series of electronic switching systems for telecommunications, for general computing purposes, and for serving as the historical software porting base for commercial UNIX.

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Wikipedia

AT&T Computer Systems

AT&T Computer Systems is the generic name for American Telephone & Telegraph's unsuccessful attempt to compete in the computer business. In return for divesting the local Bell Operating Companies (Baby Bells), AT&T was allowed to have an unregulated division to sell computer hardware and software. The company made the 3B series computers.

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TOPIC OF THE DAY

Greenwood / Black Wall Street

Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.

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TRIVIA QUESTION OF THE DAY

Who became the first Black woman to travel into space?

Mae Jemison, aboard Space Shuttle Endeavour in 1992.