Operating systems: Internals and design principles (9th edition)

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READING Operating Systems: Internals and Design Principles (9th Edition) #

Exercises #

1.1. CPU: Takes care of processing data Main memory: Volatile memory for storing data and program instructions Secondary storage: Non-volatile for permantely storing data. I/O: External peripherals such as USB drive, printer and etc.

1.2. Memory address register (MAR): specifies the memory address for the next read or write. Memory buffer register (MBR): contains data to be written to memory or receives data read from memory.

1.3. Processor-memory: Data may be transferred from processor to memory or from memory to processor. Processor-IO: Process may transfer data to I/O module or from I/O module to processor Data processing: Processor may perform arithmetic or logical operation Control: The instruction may specify a different location to fetch the next instruction from, altering the sequence of execution.

1.4. Interrupts the current execution of the CPU. This allows external peripherals to process data while the CPU works on something else. When the data processing is over, the peripheral may trigger an interrupt requesting CPU attention. A CPU interrupt handler may take care of interrupt or ignore it.

1.5. There are two types of handling interrupts: sequentially or by priority-policy. In sequential interrupts, if an interrupt happens within the handler of a current interrupt, the interrupt will be ignored for the moment by setting a pending interrupt. After it the current interrupt has been dealt, it then treats the next pending interrupt. Priority-based interrupts allows one interrupt to be handled by priority. Whiling handling one interrupt, if another interrupt occurs and the priority is higher than the current interrupt being dealt, it stores the current context and handles the higher priority interrupt.

1.6. Cost, speed, size are characteristics that are important

• Notes

  • Program execution

    A program consists of a set of instructions stored in memory. The processor fetches one instruction at a time and executes each instruction. The processing required for one instruction is called the instruction cycle. The instruction cycle is composed of three main stages:

    1. Fetch stage: The process fetches an instruction from memory. Most processor hold some type of PC (Program counter) register which points to the next instruction in memory. Each time a new instruction has been fetched, the PC is incremented to the next instruction. The fetch stage usually consists of the following “substages”
       • Address of PC is copied to the MAR (Memory address register), which either stores the memory address from where data will be fetched or the address to which data will be sent or stored.