The operating system OS

The PIPC software uses simple and affordable generic components (COTS) for its OS. The processor being X86 compatible (the most common family), the PIPC uses as an OS the DOS complemented by a DOS-Extender, allowing access to a larger memoiy area. As we speak here of COTS, and not having the source code and detailed documentation of these two software components, they are not unitarily valid . 

We will advance the following strategy with regards to safety  

Thus we can summarize the risk for both failure modes  

The PIPC offers safety barriers against these risks through the control of the integrity of the execution and of the data (section 5.8.4) and through the segregation of resources (section 5.8.5). 

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The Operating System (OS) provided by TI for the ASC is a comprehensive and advanced general purpose system. The OS operates entirely within the Peripheral Processor, scheduling and allocating system resources in a multiprogramming environment as required by the users while permitting full utilization of the Central-Processor for users problems and applications. Services provided by the OS include ... 

BIOS and Operating System. The programs within the BIOS are the first and last programs to execute whenever a computer device is turned on or off These programs interact directly with the operating system (OS). The early mainframe computers... 

The synchronization signals ensure that the outputs will not be emitted before the end of voting. These internal CSD mechanisms replace the basic mechanisms of the operating system (OS). The cyclical process, the control of the clocks and the voters ensure safety independendy from the OS. There is no particular constraint on the OS at the CSD level and a commercial VRTX core may be used. 

Workstations, a step up in capability and cost from microcomputers, usually feature a multitasking operating system (OS) enabling the computer to run more... 

The material that follows actually covers the Memory management subsection of objective 1.1 of the Operating System Technologies exam. For instructional purposes, we feel that it makes more sense to address this topic here. For complete coverage of OS objective 1.1, please also see Part II, Chapters 12 and 14. 

Operating System (OS) Provides a consistent environment for other software to execute commands. The OS gives users an interface with the computer so they can send commands to (input) and receive feedback or results back (output). To do this the operating system must communicate with the computer hardware to perform the following tasks ... 

OS was clearly superior to DOS, Microsoft and IBM announced the creation of a second PC operating system, OS/2. Unfortunately, announcing and delivering are very different things, and the story of OS/2 s production problems is a long one. We will look at both Apple and OS/2 later in the chapter. 

Part II, Chapter 12, Introduction to the Windows Interface, goes into depth on the nature of the Windows 95/98/NT/2000 interface, and overall Windows 95 OS is only marginally different from its Windows 98 upgrade, which is one of the operating systems you will be tested on during the A+ exam. As such, Windows 95 will be grouped with 98 for the rest of the book, and we will be more concerned with the differences between Windows 9x and Windows 2000 than we will be by differences between Windows 95 and Windows 98. 

The following systems or system components can be distinguished local area network (LAN), wide area network (WAN), network operating system (NOS), operating system (OS), application software, database management software, standard application software, hardware, documentation and Standard Operating Procedures (SOPs). Table 13.1 provides examples of systems and components, and the types of changes that may occur with each system or component. 

Operating systems (OS) are common to almost all computing platforms including those used in safety related systems (SRS). OS are commercial components and, as with other off the shelf components, there can be significant difficulties in assessing their dependability cost-effectively. An OS provides a broad range of support services to application software, hence it cannot easily be assessed independently of the services of the application it supports. Also many of the functions of the OS are at a low level, but are so influential to the operation of the system that they become an intrinsic aspect of deployment risk for those systems. Thus we require a specialised approach to assessing dependability of OS. 

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