An operating system allows user programs to interact with hardware by using techniques like multiprogramming and multitasking. Multiprogramming allows more than one user to use a computer at a time by having multiple ready-to-run processes from different users. If the current process stalls, the OS allocates CPU time to another process in the queue to maximize CPU utilization. Multitasking means concurrent execution of multiple processes by one user using multiple CPUs, so a user can work on a document and listen to music at the same time. Job scheduling and CPU scheduling determine which processes get allocated CPU time to make the system efficient, fast and fair.

1. Operating system
structure

2. 0
Max
Operating system
job1
job2
job3
job4

3. • An operating system is a construct that allows
the user application programs to interact with the
system hardware.
• Here,
(i) Multiprogramming – (by a single CPU)
– Multiprogramming is the ability for more than
one user to use the computer at a time using a
single CPU.
– The idea is to effectively utilize the processor to
create multiple ready-to-run
processes with each process belongs to
different user.

5. • If the current process stalls for some reason,
because it has to wait for some particular
event, the operating system allocates the CPU
to another process in the queue.
• The whole operation is facilitated by
multiprogramming operating systems to
maximize CPU utilization so that to reduce the
idle time of the CPU. The idea is to keep the
CPU busy for as long as possible.

6. Multitasking :
Multitasking means concurrent execution of
multiple processes by one user on the same
computer utilizing multiple CPUs.
For example, in a multitasking operating
system, you may work on a word document
with one program while listening to music as
the same time with another program.

8. • Job scheduling
It is the process of allocating system resources to many different
tasks by an operating system (OS).
The system handles prioritized job queues
that are awaiting CPU time and it should
determine which job to be taken from which
queue and the amount of time to be allocated
for the job.

9. • CPU scheduling :
The aim of CPU scheduling is to make the
system efficient, fast and fair. Whenever the CPU
becomes idle, the operating system must select one of the processes
in the ready queue to be executed. ... The scheduler
selects from among the processes in memory
that are ready to execute, and allocates the
CPU to one of them

10. • CPU scheduling :
The aim of CPU scheduling is to make the
system efficient, fast and fair. Whenever the CPU
becomes idle, the operating system must select one of the processes
in the ready queue to be executed. ... The scheduler
selects from among the processes in memory
that are ready to execute, and allocates the
CPU to one of them