topic 4 - operating system & computer architecture Flashcards
1
Q
what does an operating system do? (6)
A
- loads software
- Manages hardware
- Manages error handling
- Manages user accounts
- Allows multitasking
- Provides an interface
2
Q
how does interrupt work (4)
A
- A signal sent to the processor
- Requests processor time
- Processor stops to service interrupt
- Interrupts have different priorities
3
Q
name 3 devices that use interrupt
A
- Printer
- Keyboard
- Mouse
4
Q
name the 3 buses
A
- Control bus
- Address bus
- Data bus
5
Q
what does a Control bus do (3)
A
- Carries signals
- Directs the CPU
- Can be unidirectional or bidirectional
6
Q
what does an Address bus (2)
A
- Carries address locations of next item to be fetched
- Data travels one way ( unidirectional)
7
Q
what does a Data bus(2)
A
- Carries data that is being processed
- Data travels in both directions (bi-directional)
8
Q
name the 5 registers used
A
- PC; Program Counter
- MAR; Memory address register
- MDR; Memory data register
- CIR; Current instruction register
- ACC; Accumulator
9
Q
role of the control unit (4)
A
- Controls operation of memory, processor and input/output
- Fetches each instruction in turn
- Interprets instructions
- Sends signals to other components telling them what to do
10
Q
role of the ALU (arithmetic logic unit) (3)
A
- Carries out calculations
- Carries out logic operations
- Holds values during calculations in a register called an accumulator (ACC)
11
Q
explain the stored program concept
A
- Programs / instructions are stored in memory
- Data is stored in memory
- Instructions are fetched and executed one after another
12
Q
explain how execute fetch system operates (6)
A
- PC has address of next instruction to fetch
- PC copied to MAR via address bus
- Instruction copied from memory to MDR
- Instruction copied from MDR to the CIR
- Value in PC incremented to point at next instruction to fetch
- Address of instruction placed in MAR
Instruction decoded and executed
