In the previous chapter, we discussed deadlocks, resource allocation graphs, and strategies for handling deadlocks. Deadlock is a situation where some processes wait for each other's actions indefinitely, which happens in process synchronization. Operating systems use resource allocation policies to prevent and avoid deadlocks. In this chapter, we’ll discuss the various memory management techniques such as main memory, swapping, memory allocation, paging, and segmentation.
(1)Objectives
In this chapter, the student will:
1. Explain what memory management is and why it is important.
2. Be able to identify different memory management schemes and the processes they use to manage memory.
(1)Basic Concepts
Operating systems manage the computer’s memory by accomplishing two tasks. In the first task, each process must have enough memory to execute. After the process is executed, it must not invade the memory space of another process. This task requires that the operating system have memory boundaries set up. In the second task, the different types of memory in the system must be used properly so that each process is able to run effectively.
When applications are loaded into memory, they are loaded into block sizes that are determined by the operating system. For example, if the block size is 2 kilobytes (kB), then each process that is loaded into memory will be given a block of memory in the size of 2kB. Application are also loaded in these fixed block sizes with the blocks beginning and ending on the boundaries established. These blocks and boundaries ensure that the applications aren’t loaded on top of each other’s memory space.
However, most of the information that an application stores in memory is not being used at any g...
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...sm to control memory access rights on a computer and its purpose is to prevent a process from accessing memory that has not been allocated to it. All memory allocated to a process must be protected to guard against interference by other processes. This is not achieved by software, but it is achieved by implementing support from the computer's architecture: memory bound registers and memory protection keys associated with areas of memory. The memory bound registers is implemented using the lower-bound register (LBR) and the upper-bound register (UBR) in the CPU. These registers contain the beginning and ending addresses of the memory area allocated to a process. These registers are stored in the memory protection information (MPI) field of the program status word (PSW), which is an internal register to the CPU denoting the state of the computer at a moment in time.
This memory is assists in allowing the computer to simultaneously read and write data at the same time. Simply put, RAM is the most common form of memory that is utilized by computers as well as other devices. There are specific types of RAM that include dynamic random access memory and static random access memory, or DRAM and SRAM respectively. These two RAM are very different in terms of how they allow data to be read and written. Dynamic random access memory is often considered the most frequent type found in computers. Static random access memory is also found in computer, and is usually referred to as the faster of the two types due to the fact that refreshing of this form of memory is not needed whereas with dynamic random access memory it is. The term RAM is often used to describe what the computer uses to function. It is the main memory or primary memory whereby all processes and software run. Since it is random access memory, it is only available at the time a certain process is needed and is not stored anywhere on the computer specifically (2007). This is what makes random access memory often confusing to understand particular since computers also have what is known as read only
In the final chapter of The Impossible Knife of Memory, the main character of the book, Hayley begins it off talking about being in a fairytale. If this was her fairytale, this chapter would be her happily ever after. Before this chapter of the book, her life had been disorganized frequently because of her father’s disorder. Her father, Andy Kincain, a war veteran, has PTSD. Also known as Post Traumatic Stress Disorder; this disorder is caused by seeing or experiencing a very intense, and terrifying event. In Andy’s case, the war was what caused his condition.
Have you ever wondered what allows us to be aware of the present? It is actually the past! Without knowledge of past information, we would be constantly confused during the present and incapable of almost everything. Hockenbury & Hockenbury (2012) describes memory to be, “…the mental processes that enable us to acquire, retain, and retrieve information”. Without the presence of either of these three processes, the other two would be obsolete. Many experiments have been conducted to better understand these processes and break them down into their basic components.
In this experiment we replicated a study done by Bransford and Johnson (1972). They conducted research on memory using schemas. All human beings possess categorical rules or scripts that they use to interpret the world. New information is processed according to how it fits into these rules, called schemas. Bransford and Johnson did research on memory for text passages that had been well comprehended or poorly comprehended. Their major finding was that memory was superior for passages that were made easy to comprehend. For our experiment we used two different groups of students. We gave them different titles and read them a passage with the intentions of finding out how many ideas they were able to recall. Since our first experiment found no significant difference, we conducted a second experiment except this time we gave the title either before or after the passage was read. We found no significant difference between the title types, but we did find a significant difference between before and after. We also found a significant title type x presentation interaction. We then performed a third experiment involving showing objects before and after the passage was read. There we did encountersome significant findings. The importance and lack of findings is discussed and we also discuss suggestions for future studies, and how to improve our results.
One of the important components of software engineering is the platforms. There are many various types of computing platforms. A few of these include AmigaOS, Linux, Windows, Solaris. These examples are just a few of many different computing platforms. The types of computing platforms can be differentiated into three different categories, which include operating-system examples, software frame work examples, and also hardware examples. Each of the different platforms has slightly different requirements and means of maintenance. Even the required standards for the platforms differentiate depending on which platform being used. Platforms are a vital part of systems and for applications, and are available in many various forms. The basis of this paper is mainly to observe the differences and similarities of four of these platforms. The particular platforms being compared and contrasted with each other include: Linux, Microsoft Windows, UNIX, and Macintosh. The purpose is to look at the purpose of each of these platforms and also to perceive the advantages and disadvantages of each.
As the internet is becoming faster and faster, an operating system (OS) is needed to manage the data in computers. An Operating system can be considered to be a set of programed codes that are created to control hardware such as computers. In 1985 Windows was established as an operating system and a year earlier Mac OS was established, and they have dominated the market of the computer programs since that time. Although, many companies have provided other operating systems, most users still prefer Mac as the most secured system and windows as it provides more multiple functions. This essay will demonstrate the differences between windows
In the WMM memory is considered an active process and not just a passive store of information, unlike the MSM.
memory it is caused by having to slow of memory on to fast of a bus.
According to Sternberg (1999), memory is the extraction of past experiences for information to be used in the present. The retrieval of memory is essential in every aspect of daily life, whether it is for academics, work or social purposes. However, many often take memory for granted and assume that it can be relied on because of how realistic it appears in the mind. This form of memory is also known as flashbulb memory. (Brown and Kulik, 1977). The question of whether our memory is reliably accurate has been shown to have implications in providing precise details of past events. (The British Psychological Association, 2011). In this essay, I would put forth arguments that human memory, in fact, is not completely reliable in providing accurate depictions of our past experiences. Evidence can be seen in the following two studies that support these arguments by examining episodic memory in humans. The first study is by Loftus and Pickrell (1995) who found that memory can be modified by suggestions. The second study is by Naveh-Benjamin and Craik (1995) who found that there is a predisposition for memory to decline with increasing age.
Virtualization technologies provide isolation of operating systems from hardware. This separation enables hardware resource sharing. With virtualization, a system pretends to be two or more of the same system [23]. Most modern operating systems contain a simplified system of virtualization. Each running process is able to act as if it is the only thing running. The CPUs and memory are virtualized. If a process tries to consume all of the CPU, a modern operating system will pre-empt it and allow others their fair share. Similarly, a running process typically has its own virtual address space that the operating system maps to physical memory to give the process the illusion that it is the only user of RAM.
This element governs the memory I/O, before it was located on separate chip but now it is located inside the processer providing faster communication between the two components, this means more bandwidth and cutting down memory latency. Memory channel supports three channels of DDR3 memory; this means you must have a multiple of three dual in line memory module (DIMM), which comprises a series of dynamic random access memory then comes the memory frequency where the memory DIMM can operate on various frequencies: 1333MHz/1066MHz/800MHz, the frequency is proportional to the bandwidth and performance, thus the higher the frequency the higher the bandwidth and performance but under conditions:
According to Microsoft, the simplest definition of a process is an executed program. A thread is “the basic unit to which the operating system allocates processor time”. A thread can “execute any part of the process code, including parts currently being executed by another thread”. In Windows, threads share its virtual address space and system resources. Unlike the conceptual model, each thread “maintains exception handlers, a scheduling priority, thread local storage, a unique thread identifier and a set of structures the system will use to save the thread context until it is scheduled”. Like the conceptual model of a thread, Windows’ threads do not share registers and stack resources. This is because the thread context includes “the thread’s set of machine registers, the kernel stack, a thread environment lock and a user stack in the address sp...
The field of Operating Systems acquainted me with a whole new array of ideas. To understand those concepts better, I worked with ‘Minix’ operating systems which ...
Computers are very complex and have many different uses. This makes for a very complex system of parts that work together to do what the user wants from the computer. The purpose of this paper is to explain a few main components of the computer. The components covered are going to be system units, Motherboards, Central Processing Units, and Memory. Many people are not familiar with these terms and their meaning. These components are commonly mistaken for one and other.
There are four types of memory. These are the RAM, ROM, EEPROM and the Bootstrap loader. The RAM, also known as Random Access Memory, is the temporary space where the processor places the data while it is being used. This allows the computer to find the information that is being requested quickly without having to search the hard drive space. Once the information has been processed, and stored onto a permanent storage device, it is cleared out of the RAM. The RAM also houses the operating system while in