import random

import time

import threading

MEMORY$\_$SIZE $=1024$

memory $=[0]*$ MEMORY$\_$SIZE

DEVICES $=\{$

$$ "keyboard": $\{"$address$"$: $0$x$100,$ "size": $4\},$

$$ "display": $\{"$address$"$: $0$x$104,$ "size": $4\},$

$$ "storage": $\{"$address$"$: $0$x$108,$ "size": $4\},$

$$ "network": $\{"$address$"$: $0$x$10$c$,$ "size": $4\},$

$$ "dma": $\{"$source$\_$address": $0$x$200,$ "dest$\_$address":$0$x$300,$"size": $8\},$

$\}$

print$($f$"$Memory initialized with size: $\{$MEMORY$\_$SIZE$\}$ bytes and devices mapped."$)$

print$($f$"$Keyboard address: $\{$DEVICES$[\text{'}$keyboard$\text{'}][\text{'}$address$\text{'}]\}")$

print$($f$"$Display address: $\{$DEVICES$[\text{'}$display$\text{'}][\text{'}$address$\text{'}]\}")$

print$($f$"$Storage address: $\{$DEVICES$[\text{'}$storage$\text{'}][\text{'}$address$\text{'}]\}")$

print$($f$"$Network address: $\{$DEVICES$[\text{'}$network$\text{'}][\text{'}$address$\text{'}]\}")$

print$($f$"$DMA source address: $\{$DEVICES$[\text{'}$dma$\text{'}][\text{'}$source$\_$address'$]\}")$

print$($f$"$DMA destination address: $\{$DEVICES$[\text{'}$dma$\text{'}][\text{'}$dest$\_$address'$]\}")$

print$($f$"$Total memory$-$mapped I$/$O addresses: $\{$len$($DEVICES$)\}")$

def keyboard$\_$input$()$:

$$ return random.choice$(\text{'}$ABCDEFGHIJKLMNOPQRSTUVWXYZ$\text{'})$

def display$\_$output$($data$)$:

$$ print$($f$"$Display: $\{$data$\}")$

def disk$\_$io$()$:

$$ time.sleep$(2)$

$$ print$("$Disk I$/$O completed"$)$

def network$\_$io$()$:

$$ time.sleep$(1\mathrm{.}5)$

$$ print$("$Network I$/$O completed"$)$

input$\_$data $=$ keyboard$\_$input$()$

display$\_$output$($input$\_$data$)$

disk$\_$io$()$

network$\_$io$()$

memory$\_$lock $=$ threading.Lock$()$

def prioritized$\_$io$()$:

$$ KEYBOARD$\_$ADDRESS $=$ DEVICES$[\text{'}$keyboard$\text{'}][\text{'}$address$\text{'}]$

$$ DISPLAY$\_$ADDRESS $=$ DEVICES$[\text{'}$display$\text{'}][\text{'}$address$\text{'}]$

$$ while True:

$$ with memory$\_$lock:

$$memory$[$KEYBOARD$\_$ADDRESS$]=$ ord$($keyboard$\_$input$())$

$$ if random.random$()>0\mathrm{.}7$:

$$ print$("$Urgent task! Handling network I$/$O$...")$

$$ network$\_$io$()$

$$ with memory$\_$lock:

$$memory$[$DISPLAY$\_$ADDRESS$]=$ memory$[$KEYBOARD$\_$ADDRESS$]$

$$ display$\_$output$($chr$($memory$[$DISPLAY$\_$ADDRESS$]))$

$$ if random.random$()>0\mathrm{.}5$:

$$ threading.Thread$($target$=$disk$\_$io$).$start$()$

$$ time.sleep$(0\mathrm{.}5)$

io$\_$thread $=$ threading.Thread$($target$=$prioritized$\_$io$)$

io$\_$thread.start$()$

DMA$\_$SOURCE$\_$ADDRESS$\_1=0$x$00$

DMA$\_$DESTINATION$\_$ADDRESS$\_1=0$x$10$

DMA$\_$SOURCE$\_$ADDRESS$\_2=0$x$20$

DMA$\_$DESTINATION$\_$ADDRESS$\_2=0$x$30$

DMA$\_$BLOCK$\_$SIZE $=16$

def dma$\_$transfer$($source$,$ destination$)$:

$$for i in range$($DMA$\_$BLOCK$\_$SIZE$)$:

$$ with memory$\_$lock:

$$memory$[$destination $+$ i$]=$ memory$[$source $+$ i$]$

$$print$($f$"$DMA: Transffered $\{$memory$[$destination $+$ i$]\}$ to address $\{$destination $+$ i$\}")$

$$ time.sleep$(0\mathrm{.}1)$

def start$\_$dma$\_$transfers$()$:

$$thread$\_1=$ threading. Thread$($target$=$dma$\_$transfer, args$=($DMA$\_$SOURCE$\_$ADDRESS$\_1,$ DMA$\_$DESTINATION$\_$ADDRESS$\_1))$

$$thread$\_2=$ threading. Thread$($target$=$dma$\_$transfer, args$=($DMA$\_$SOURCE$\_$ADDRESS$\_2,$ DMA$\_$DESTINATION$\_$ADDRESS$\_2))$

$$thread$\_1.$start$()$

$$thread$\_2.$start$()$

$$thread$\_1.$join$()$

$$thread$\_2.$join$()$

start$\_$dma$\_$transfers$()$

io$\_$thread.join$()$

explain this code in words $.$