knowt logo

CH 04 : Operating Systems And Computer Architecture

Operating Systems

  • Operating System(OS): It is a computer software running in the background when the computer is on, and performs various operations.

    • It is also responsible for the communication between hardware and software.

    • Operating systems make it alot easier to use computers.

  • Some of the tasks an OS performs:

    • Multitasking

    • Multiprogramming

    • Error handling

    • Loading and running software

    • Memory management

    • Security (passwords etc)

    • Input and output control

  • Windows and Linux are examples of OS.

  • When a computer is turned on:

    • The initial starting programs are loaded from Read Only Memory(ROM),

    • Different components of the computer are checked for errors,

    • The OS is loaded into the computer memory.


Interrupts And Buffers

  • Interrupt: It is a signal sent to the Processor from a device or software, to make the Processor temporarily stop its current operation and service another.

    • An Interrupt is sent when for example, a page is jammed in the printer, or when a software error occurs.

    • Interrupts allow computers to multitask.

    • When an Interrupt occurs, the status of the currently running task is saved using an Interrupt Handler. so that the processor can resume it after the Interrupt is serviced.

  • Buffer: It is a temporary memory area.

    • Buffers are filled from computer memory and emptied to the hardware, allowing the processor to perform other tasks in the meanwhile.

  • Example to explain how Buffers and Interrupts are used together, while a printer is being used:


Computer Architecture

  • Von Neumann Architecture: A computer system which can store programs in a memory. The idea was developed by John von Neumann.

    • Before Neumann, computers had to be fed data while they were running, so for every task the data had to be fed immediately before-hand.

  • In a von Neumann system, a Memory Unit, Processor(containing a Control Unit) and the hardware are connected through Buses to perform different tasks.

  • Buses: The connections which transport data around the system and also maintain data synchronization.

    • Address Bus: Unidirectional Bus carrying signal related to the addresses of the memory contents.

    • Data Bus: Bidirectional Bus responsible for moving the data and contents of the memory around the system.

    • Control Bus: Unidirectional Bus carrying signals related to control and coordination of all activities in the computer.

  • Registers: High speed storage areas within the computer system, which are needed to store and manipulate data.

    • Memory Address Register(MAR): Address which contains the location of the memory contents.

    • Memory Data Register(MDR): Register which contains the content from memory.

    • Arithmetic Logic Unit(ALU): Register which allows the calculations and logic operations to be performed within the computer.

    • Program Counter(PC): Register which contains the instructions for the next task to be performed.

    • Current Instruction Register(CIR): Register which contains the instructions for the current task.

  • Memory Unit: It contains all the data to be processed and its addresses as well.

  • Processor: The part where data is processed and the necassary logic operations are carried out.

  • Control Unit: It controls the operation of the memory, processor and input/output devices.

    • Control Unit reads an instruction from memory and tells the other components how to function, through Control Bus.

  • Input/Output Devices: Ways of feeding data into a computer and/or getting it out.


Fetch-Execute Cycle

  • To perform a task, instructions for the said task are Fetched from the memory and Processed before being Executed.

  • Fetch:

    • Instructions for the next task are fetched from the PC and put into CIR through Data Bus.

    • PC is incremented by 1.

    • Instructions are sent to the Processor(through Data Bus) to be decoded.

  • Execute:

    • Processor sends the decoded instructions as control signals using the Control Bus, to other components of the system, so that the instructions can be executed.

CH 04 : Operating Systems And Computer Architecture

Operating Systems

  • Operating System(OS): It is a computer software running in the background when the computer is on, and performs various operations.

    • It is also responsible for the communication between hardware and software.

    • Operating systems make it alot easier to use computers.

  • Some of the tasks an OS performs:

    • Multitasking

    • Multiprogramming

    • Error handling

    • Loading and running software

    • Memory management

    • Security (passwords etc)

    • Input and output control

  • Windows and Linux are examples of OS.

  • When a computer is turned on:

    • The initial starting programs are loaded from Read Only Memory(ROM),

    • Different components of the computer are checked for errors,

    • The OS is loaded into the computer memory.


Interrupts And Buffers

  • Interrupt: It is a signal sent to the Processor from a device or software, to make the Processor temporarily stop its current operation and service another.

    • An Interrupt is sent when for example, a page is jammed in the printer, or when a software error occurs.

    • Interrupts allow computers to multitask.

    • When an Interrupt occurs, the status of the currently running task is saved using an Interrupt Handler. so that the processor can resume it after the Interrupt is serviced.

  • Buffer: It is a temporary memory area.

    • Buffers are filled from computer memory and emptied to the hardware, allowing the processor to perform other tasks in the meanwhile.

  • Example to explain how Buffers and Interrupts are used together, while a printer is being used:


Computer Architecture

  • Von Neumann Architecture: A computer system which can store programs in a memory. The idea was developed by John von Neumann.

    • Before Neumann, computers had to be fed data while they were running, so for every task the data had to be fed immediately before-hand.

  • In a von Neumann system, a Memory Unit, Processor(containing a Control Unit) and the hardware are connected through Buses to perform different tasks.

  • Buses: The connections which transport data around the system and also maintain data synchronization.

    • Address Bus: Unidirectional Bus carrying signal related to the addresses of the memory contents.

    • Data Bus: Bidirectional Bus responsible for moving the data and contents of the memory around the system.

    • Control Bus: Unidirectional Bus carrying signals related to control and coordination of all activities in the computer.

  • Registers: High speed storage areas within the computer system, which are needed to store and manipulate data.

    • Memory Address Register(MAR): Address which contains the location of the memory contents.

    • Memory Data Register(MDR): Register which contains the content from memory.

    • Arithmetic Logic Unit(ALU): Register which allows the calculations and logic operations to be performed within the computer.

    • Program Counter(PC): Register which contains the instructions for the next task to be performed.

    • Current Instruction Register(CIR): Register which contains the instructions for the current task.

  • Memory Unit: It contains all the data to be processed and its addresses as well.

  • Processor: The part where data is processed and the necassary logic operations are carried out.

  • Control Unit: It controls the operation of the memory, processor and input/output devices.

    • Control Unit reads an instruction from memory and tells the other components how to function, through Control Bus.

  • Input/Output Devices: Ways of feeding data into a computer and/or getting it out.


Fetch-Execute Cycle

  • To perform a task, instructions for the said task are Fetched from the memory and Processed before being Executed.

  • Fetch:

    • Instructions for the next task are fetched from the PC and put into CIR through Data Bus.

    • PC is incremented by 1.

    • Instructions are sent to the Processor(through Data Bus) to be decoded.

  • Execute:

    • Processor sends the decoded instructions as control signals using the Control Bus, to other components of the system, so that the instructions can be executed.

robot