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42 Cards in this Set
- Front
- Back
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What is an operating system?
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An operating system is a program that manages computer hardware, provides a basis for applications programs, and acts as an intermediary between computer user and hardware. They are designed for some combination of ease of use and efficiency.
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How do operating design specs differ between mainframes, tablets, and personal computers?
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Mainframes for efficiency, tablets are designed for convenience, and personal computers are designed for both efficiency and convenience.
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How would you define an operating system from a system view?
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An operating system is a resource allocator-not only does it manage resources but it decides between conflicting requests for efficient and fair resource use.
An operating system is also a control program that controls execution of programs to prevent errors and improper use of the computer. |
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What is a bootstrap program?
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A bootstrap program is a program loaded at power-up or reboot.
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How do device controllers connect to the CPU(s)?
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They are connected through a common bus that provides access to shared memory.
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With respect to time, how are CPUs, devices competition for memory cycles, and I/O executed?
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They are executed concurrently.
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What is a device controller?
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A controller that is in charge of a particular device type that has a local buffer.
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From where and to where does the CPU move data?
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The CPU moves data between the main memory and local buffers.
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From where to where does the I/O occur?
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I/O occurs between the device to the local buffer of the controller.
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How do device controllers inform the CPU that it has finished its operation?
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The device controller informs the CPU that it has finished its operation by causing an interrupt.
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How do interrupts work?
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Interrupt transfers control the interrupt service routine through the interrupt vector, which contains the addresses of all the service routines.
The interrupt architecture must save the address of the interrupted instruction. Incoming interrupts are disabled while another interrupt is are diabled while another interrupt is being processed to prevent a lost interrupt. |
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What is a trap?
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A trap is a software-generated interrupt caused by either an error or a user request.
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Are operating systems interrupt driven?
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Yes, operating systems are interrupt driven.
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How do operating systems handle interrupts?
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The operating system preserves the state of the CPU by storing all registers, including the program counter. It then determines the type of interrupt and separates segments of code to determine what action should be taken per interrupt.
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What are two ways to handle interrupts?
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The two ways to handle interrupts are through polling or a vectored interrupt system.
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What are two I/O methods?
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Two common I/O methods are synchronous and asynchronous processing.
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What is the synchronous I/O process?
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With the synchronous I/O structure, control returns to the user program upon I/O completion. In fact, there is a wait instruction that idles the CPU until the next interrupt.
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What is the asynchronous I/O process?
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After the I/O starts, the control returns to the program without waiting for completion. Examples: system calls, device-status table
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Describe the direct memory access structure.
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This structure is used for high-speed I/O devices able to transmit information at close to memory speeds.
Device controller transfers blocks of data from buffer storage directly to main memory without CPU intervention. Only one interrupt is generated per block, rather than the one interrupt per byte. |
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Describe computer storage structure
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The storage structure consists of the main memory, second storage and magnetic disks. The disk is then divided into tracks, which are divided into sectors.
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What is main memory?
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Main memory is the only large storage media that the CPU can access directly.
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What is secondary storage?
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Second storage is the extension of main memory that provides large nonvolatile storage capacity.
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What are magnetic disks?
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They are rigid metal or glass platters covered with magnetic recording material that are divded into tracks and sectors. Interaction between the magnetic disks and the computer are governed by the disk controller.
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In order of top to bottom, what is the storage hierarchy order?
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1. Registers
2. Cache 3. Main memory 4. Electronic disk 5. Magnetic disk 6. Optical disk 7. Magnetic tapes |
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How is the storage hierarchy organized?
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The storage hierarchy is organized in terms of speed, cost, and volatility.
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What is caching?
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Caching is copying information into a faster storage system. Main memory can be viewed as a last cache for secondary storage.
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How does caching work?
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The cache is checked first. Only if the information is not in the cache is it taken from elsewhere, cached, and then used.
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What makes caching difficult?
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The cache is smaller than the storage being cached. Therefore, you need to deal with the size and how to replace items in the cache.
Also, since multiple copies of data exist, one must be sure that the CPU always has the most recent value. |
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What are the three architecture groups?
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1. Single-processor systems
2. Multiprocessor systems 3. Clustered systems |
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What are some advantages of multiprocessor systems?
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1. Increased throughput
2. Economy of scale 3. Increased reliability |
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What are some features of clustered systems?
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1. Linked via LAN
2. Provide high availability 3. High-performance computing (parallelization) 4. Distributed Lock Manager (DLM) |
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What is multiprogramming and why is it needed?
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Multiprogramming organizes jobs so that the CPU always has one to execute. This is because a single user cannot keep CPU and I/O devices busy at all times. A subset of the total jobs in the system is kept in memory and what is run is chosen by job scheduling. When the system is waiting on one job, it switched to another.
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What is timesharing?
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Timesharing, or multitasking is a logical extension in which the CPU switches jobs so frequently that users can interact with each job while it is running, creating interactive computing.
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What are some prerequisites for timesharing?
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1. Near instantaneous response time
2. Scheduling 3. Processes 4. Swapping. 5. Virtual memory |
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What is an advantage of virtual memory?
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Virtual memory allows execution of processes not completely in memory.
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What are the two modes used in dual mode operation?
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User mode and kernel mode.
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How does one tell the difference between user and kernel mode?
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The hardware provides a mode bit to tell when the system is running user or kernel code. Some instructions are privileged
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How do you change between kernel and user mode?
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There's a system call that changes the mode bit to indicate kernel mode, and the recall resets it to user mode.
There is also a timer to prevent any infinite loops or resource hogging. |
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What is the difference between a program and a process?
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A program is a passive entity. A process is an active entity,
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What resources does a process need?
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CPU, memory, I/O, files, initialization data
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What is required on process termination?
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Freeing of any reusable resources
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How many program counters exist per process?
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There is one program counter per thread. Hence, single-threaded processes have one program counter
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