Multiprogramming

The Third Generation (1965-1980) ICs and Multiprogramming
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The Third Generation (1965-1980) ICs and Multiprogramming

By the early 1960s, the majority of computer manufacturers had two different, incompatible, product lines. On the one hand there were the word-oriented, large-scale scientific computers, such as the 7094, which were used for numerical calculations in science and

Smart Card Operating Systems
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Smart Card Operating Systems

The smallest operating systems run on smart cards, which are credit cardsized devices containing a CPU chip. They have very severe processing power and memory limitations.

OPERATING SYSTEM CONCEPTS - PROCESSES
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OPERATING SYSTEM CONCEPTS - PROCESSES

The majority of operating systems provide certain essential concepts and abstractions such as processes, address spaces, and files that are most important to understanding them. In

Protection Hardware
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Protection Hardware

Early mainframes, like the IBM 7090/7094, had no protection hardware, so they just ran one program at a time. A buggy program could wipe out the operating system and easily crash

Layered Systems
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Layered Systems

A generalization of the approach of figure in previous article i.e. "OPERATING SYSTEM STRUCTURE" is to organize the operating system as a hierarchy of layers, each one constructed upon the one below it. The first system constructed in this way was the THE

VM/370
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VM/370

This system, initially called CP/CMS and later renamed VM/370 (Seawright and MacKinnon, 1979), was based on an astute observation: a timesharing system provides (1)

The Java Virtual Machine  /  Exokernels
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The Java Virtual Machine / Exokernels

One more area where virtual machines are used, but in a somewhat different way, is for running Java programs. When Sun Microsystems invented the Java programming language, it also invented a virtual machine (i.e., a computer architecture)

PROCESSES AND THREADS
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PROCESSES AND THREADS

We are now about to start a detailed stu`dy of how operating systems are designed and created. The most essential concept in any operating system is the process: an abstraction of

The Process Model
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The Process Model

In this model, all the runnable software on the computer, sometimes including the operating system, is organized into a number of sequential processes, or just processes for short. A process is just an example of an executing program, including the current values of the program

Modeling Multiprogramming
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Modeling Multiprogramming

When multiprogramming is used, the CPU utilization can be improved. Crudely put, if the average process computes only 20% of the time it is sitting in memory, with five processes in memory at once, the CPU should be busy all the time. This model is unrealistically hopeful,

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