Operating Systems and Computer Architecture
- Created by: answersindna
- Created on: 18-12-18 14:18
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- Operating Systems and Computer Architecture
- Operating Systems
- essentially the software running in the background of a computer system
- without this many computers wouldn't be user friendly
- it manages the basic functions of a computer
- e.g. human computer interface, multitasking, batch processing, security, error handling
- e.g. windows
- Only loaded onto memory is ROM's initiating programs find no errors, in checking procedure
- simple devices with embedded microprocessors - may not have os
- essentially the software running in the background of a computer system
- Interrupts and Buffers
- interrupt = signal sent from device to processor that causes the processor to stop and attend to interrupt
- can occur when: disk drive is ready to receive more data, an error has occurred, a user has pressed a key that interrupts the process, a software error has occurred
- when this is received the processor will either stop task entirely or continue task
- whenever an interrupt is serviced the previous task's progress is saved using an INTERRUPT HANDLER
- allows for many windows to be open simultaneously
- Buffers = used in computers as temporary memory area. Essential because hardware devices operate slower than the processor.
- buffers ensure that the processors don't spend their time waiting for the hardware
- often used together
- interrupt = signal sent from device to processor that causes the processor to stop and attend to interrupt
- Computer Architecture
- Von Neumann
- idea of a stored program computer. Means many programs/data are held in memory and then moves between memory unit and processor
- control unit
- controls operations of the memory, processor and input/output devices
- reads instruction, interprets instruction, sends signals using control bus
- input and output devices
- main method of entering and receiving data in computer systems
- input = convert external data into a form that the computer can understand and process
- output devices = show the results of computer processing in a way humans can understand
- control unit
- idea of a stored program computer. Means many programs/data are held in memory and then moves between memory unit and processor
- buses
- data bus
- bi-directional sends data between mu and p and input and output
- control bus
- unidirectional and bi-directional, carries signals relating to control and coordination of activities
- address bus
- unidirectional, carries signals relating to address between the mu and the p
- address = were data is stored
- unidirectional, carries signals relating to address between the mu and the p
- data bus
- registers
- needed to manipulate data within the computer
- high speed storage area within a computer, all data must be represented in a register prior to processing
- memory unit
- made up of a number of partitions
- each partition has an address and its contents
- contents = binary stored in the location
- each partition has an address and its contents
- MAR = memory address register MDR= memory data register ALU= arithmetic and logic unit PC = program counter CIR= current instruction register
- MAR and MDR
- the memory location is sent to the MAR first
- then read signal = sent to computer memory using a control bus
- then contents is sent to MDR
- for a write function = order same but MAR assigns a memory location
- then contents is sent to MDR
- then read signal = sent to computer memory using a control bus
- the memory location is sent to the MAR first
- ALU stored in processor
- MAR and MDR
- made up of a number of partitions
- Von Neumann
- Fetch-Execute Cycle
- to carry out a set of instructions
- processor = fetches some data from memory and stores them in suitable registers
- both address and memory bus are used
- MAR -> PC-> CIR
- pc = incremented before next instruction can be processed
- execute = happens after the instructions are decoded
- processor passes the decoded instructions as a set of control signals to the appropriate computer system components
- 1. PC - contains address of the memory location of the next instruction to be fetched
- 2. address copied to MAR using address bus
- 3. instructions at MAR temp. copied to MDR
- 4.contents of MDR copied to CIR
- 5.PC value incremented - points to next instruction
- 6. instruction finally decoded + executed
- 5.PC value incremented - points to next instruction
- 4.contents of MDR copied to CIR
- 3. instructions at MAR temp. copied to MDR
- 2. address copied to MAR using address bus
- 1. PC - contains address of the memory location of the next instruction to be fetched
- processor passes the decoded instructions as a set of control signals to the appropriate computer system components
- pc = address of the next instruction CIR = current instruction being processed
- Operating Systems
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