OS WHAT AND WHY.txt

OS IS A SOFTWARE THAT PROVIDES INTERFACE BETWEEN USER AND HARDWARE
HARD LIKE CPU,I/O DEVICES-keyboard etc,RAM 

#if os did not exist
we cant directly access the devices ,for that we need to write that certain specific
that allows us to access that certain hardware 

now in that sense we would have to write many programs many times for each time we 
want to use that hardware which is a pain

if we wanted to print something we could not print directly we would have to write
programs each time

for these few reasons we made os

#primary functionality of OS-to provide a convenience and efficieny to the user
convenience when we want to make stuff easier for us to do,like not having to
write the same program again and again to do something

windows used to have the highest convenience

now problems started becoming very complex and user wanted them to be easy
so we see throughput
           throughput=no of task/time
now we want an os with high throughput 
now linux has a very high throughput as compared to windows 

#funtionality of os- \
1 RESOURCE MANAGEMENT-like in servers we can decide who can get what hardware
or software using a certain type of os 
like task manager also shows us what the os is managing
specially used in parallel processing  as in windows its default but in parallel
we can decide while working on the same data with multiple people who gets what

2 process management-we open many programs at the same time,how what starts,what 
memory it takes how it works so other programs can also work with ease without
 any problems and taking care of all that 

how it works??-cpu scheduling-we use various cpu schedulers to know when and how
will that process work

3 storage management-secondary devices like harddisk-how to manage/store all the
data being put in the device and where and how to store it 
done through file system -manages how data will be stored permanently

4 memory management-RAM -ALL THE PROCESSES FIRST COME IN RAM,THEN WE GIVE THEM 
TO CPU ONE BY ONE,THS OS NEEDS TO DECIDE HOW MUCH MEMORY TO GIVE TO WHAT PROGRAM
AND TO TAKE THAT MEMORY BACK AFTER PROGRAM ENDS

NOTE-MEMORY AND STORAGE MANAGEMENT ARE DIFFERENT BECAUSE RAM HAS SIZE CONSTRAINT
WHEREAS HDD SDD HAS NO SIZE CONSTRAINTS ,WE NEED TO ALLOW CERTAIN PROGRAMS TO RUN
FOR CERTAIN TIME IN RAM AND THEN END THEM,THIS IS RAM

5 SECURITY AND PROVACY-EXAMPLE PASSWORD ,to secure our data ,windows uses kerberos
security protocol, other than password like when some process gets cpu in the ram
and takes some memory and tries to run some code out of its needed things like
malware etc the antivirus can block it or the built in os privacy and security
programs 


LAST NOTE-NOW WHEN WE OPEN ANY FOLDER OR DO ANYTHING LIKE TRYING TO PRINT SOMETHING 
USING PRINT FUNCTION IN ANYTHING LIKE ADOBE OR STRAIGHT IN THE PRINTER APPLICATION
WE JUST DOUBLE CLICK OR PRESS ENTER BUT IN ACTUALITY WHAT WE ARE DOING ARE GIVING 
SYSTEM CALLS IN THE OPERATING SYSTEM THROUGH APPLICATIONS WHICH THEN LET US ACCESS
HARDWARE,SYSTEM CALLS ARE LIKE RIGHTS WHICH WE CAN HAVE TO USE HARDWARE
LIKE WHEN WE OPEN A FOLDER WE USE THE OPEN SYSTEM CALL

NOW WE CAN DURECTLY USE SHELL TO ACCESS THE SYSTEM OR KERNEL AND GIVE DIRECT 
SYSTEM CALLS AND NOT THROUGH ANY APPLICATION


USER->APPLICATION->OPERATING SYSTEM->HARDWARE