Chapter 4 - Operating systems and computer architecture
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Define Operating System
the software running in the background of a computer system - it manages many of the basic functions
What is an interrupt?
a signal sent from a device (or other software) to the processor requesting its attention
What is a buffer?
a temporary memory area in a device
Define computer architecture
how a computer system is designed
What do buses do?
buses move data around the computer and also send out control signals to synchronise the internal operations
What are registers?
high-speed storage areas within the computer
What is a memory unit made up of?
it is made up of addresses and contents
What is a control unit?
it controls the operation of the memory, processor and input/output devices
Give 5 examples of operations/tasks Operating Systems do
human-computer interface (HCI) multitasking multiprogramming batch processing error handling load/run applications management of user accounts file utilities processor management memory management real-time processing interrupt handling security input/output control
What are examples of devices that do not require an operating system?
ovens washing machines
Why do some devices not need an operating system?
they carry out simple, unchanging tasks which are initiated by a user pressing a button
What do interrupts cause the processor to do?
temporarily stop what it is doing and service the interrupt
Why are buffers used?
to compensate for the slower operating speed of peripherals when compared to a processor
What do buffers allow processors to do?
to carry on with other tasks
What is an example where buffers are used?
printers music/video streaming
What is the von neumann architecture?
a concept that holds programs and data in memory data moves between the memory unit and processor between processor, memory unit and input/output devices
What does an address bus do?
carries signals relating to addresses between the processor and memory uni-directional
What does a data bus do?
sends data between the processor, memory unit and the input/output devices bi-directional
What does a control bus do?
carries signals relating to control and coordination of all activities within the computer, it can be uni-directional or bi-directional due to internal connections
Where must data be represented before it is processed?
in registers
What are 5 different types of registers in the von neumann architecture?
Memory address register (MAR) Memory data register (MDR) Arithmetic and Logic Unit (ALU) Program counter (PC) Current Instruction Register (CIR)
What does a control unit do?
read instructions interprets instructions sends out signals along control bus to synchronise all computer components
What does the fetch part of the fetch execute cycle entail?
the next instructions are fetched from the memory address stored in the PC this is then stored in the CIR the PC is incremented by so the next instruction can be processed
What does the execute part of the fetch execute cycle entail?
the decoded instruction is then passed as a set of control signals to the appropriate components of the computer system