Operating System Fundamentals

Operating System Fundamentals
63 Key Terms Access time Base address Best fit First fit First In First Out (FIFO) Fragmentation Hit Hit ratio Least Frequently Used
(LFU) Least Recently Used (LRU) Logical address Main memory Memory manager Page Page fault Page file Page request Page table Paging device Physical memory Random replacement Relative address Relocation Replacement policy Second Chance Swap file Swapping Thrashing Virtual memory Virtual memory space Windows Ready Boost Worst fit


Review Questions
1. What is the purpose of the memory manager in an operating system
2. What types of problems must the memory manager protect against in a multiprogramming system
3. Describe any two memory allocation strategies.
4. What is fragmentation and what causes it
5. What is virtual memory and what does it try to accomplish
6. Explain insteps how virtual memory works.
7. What is a replacement policy use for
8. Describe any three (3) replacement policies.
9. There are 5 replacement policies. Which seems the simplest to implement Why (If it is
easy to explain, it is usually easy to implement or program) Of the five (5) replacement policies, which seems the most difficult to implement Why Which policy do you think has the best hit ratio Why

Operating System Fundamentals
64
Unit 5: Input/Output
What are Input/Output Resources
Input/Output devices were briefly discussed in Unit 1: Architecture Review. Input devices are any devices that allow data to be input into a computer system. The most common examples are the keyboard and mouse, although there are many others. Output devices are any devices to which the computer can send output data, such as the monitor or printer. These IO devices are connected to the CPU by a series of system busses on the motherboard. The operating system is responsible for issuing commands to IO devices, as well as handling all interrupts and errors generated by the devices. The operating system needs someway to efficiently manage all of these devices and the flow of data coming in from them, or going out to them. These responsibilities are complicated by the fact that many processes being executed by the operating system may need to share the same I/O resources. In this unit, we will examine IO resource management from two perspectives. First, we will look at IO resource management from a hardware management perspective. We will examine the role of device controllers, as well as the differences between
preemptable and non-preemptable IO resources, and block and character IO devices. Later in the unit, we will take a detailed look at the actual management of one of the most common IO hardware devices in any computer system magnetic storage devices (hard disks and floppy disks. We will also be examining IO resource management from a software perspective. We will take a look at the role of IO management software, and IO software system layers. This will include an examination of the software operating at each layer. In particular, we will focus on the role and structure of device drivers. We will conclude this unit with a brief look at the role of the system
clock in the management of IO resources. IO Resources
Input/Output resources are any IO devices (and their supporting hardware and software components) that are available for use by processes being executed by the operating system. These resources are frequently shared between processes, so the operating system must have someway to regulate access to the resources to prevent conflicts and deadlocks. The operating system uses device controllers to handle communications with IO devices. IO resources can be categorized as either preemptable or non-preemptable. In addition to regulating access to IO resources, the operating system must also control how data is transmitted to and from IO devices. Data transmission can be handled as either character or block transmission, depended upon the type of IO device.

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