week 1

Question 1

multiplexing

Answer 1

sharing of resources over time and space

Question 2

basic cycle of the CPU

Answer 2

fetch instruction from memory
decode instruction to determine type and operands
execute instruction

Question 3

general registers

Answer 3

contained within CPU
holds key variables and temporary results
used because accessing memory is a time expensive operation

Question 4

special registers

Answer 4

registers in CPU with specific purposes
visible to the programmer

eg.
PC: program counter, contains memory address of the next instruction to be fetched
SP: stack pointer, points to the top of the current stack in memory
PSW: program status word, contains condition bits set by comparison instructions, CPU priority, mode, other control bits

Question 5

pipeline

Answer 5

organisation where CPU is designed to split up tasks to execute more than one instruction at a time

Question 6

kernel vs user mode

Answer 6

in kernel mode the CPU can execute every instruction and access every hardware
user mode: limited access

Question 7

system call

Answer 7

method in which the user can request to obtain services from the OS i.e. services that run in kernel mode