Os

Complier, assembler, text editor and database system

Efficient management of the hardware,

Makes computer more convienent to use for end user,

Make problem solving easier for programmers

Dual mode operation allows OS to protect itself and other system components. The 2 modes are user mode and kernel mode

It provides the ability to distinguish when system is running user or kernel code. Some instructions are desginatd as priveleged which is only in kernel mode

It is a programming interface to the services provided by the OS, typically written in a high level language

It is divided in layers/levels that uses modularity so that each layer uses funcrions and services of lower-level layers.

Benefits: modular so it is simple to construct and debug, high level interfaces are easier to program

Drawbacks: too many layers increase performance overhead, lower levels are difficult to extend

It aims to provide communicarion facility between client program and services running in user space. Communication takes place between user modules using message passing. Client and service never interact directly, they communicate exchanging msgs with the microkernel

Benefit: Easier to extend, easier to port OS with new architecture, more reliable

Drawback: performance overhead of user space to kernel space communication

Uses object oriented approach, each core component is seperated and talks over known interfaces, each loadable as needed within kernel

Stores information associated with each process (task control block)

Location of next executable instruction

Contents of all processes centric registers

Context switch is used when CPU switches to another process by saving the state of the old process ans loads the saved state for the new process. The context of a process represented in the PCB

Allow communication in standard producer-consumer style. Producer writes to one end, consumer reads the other end. Pipes are unidirectional and require a parent-child relationship

May allow continued execution if part of process is blocked

threads share resources of processes, easier than shared memory or message passing

Cheaper than process creation, thread switching lower overhead than context switch

Process can take advantage of multiprocessor architectures

Int value over unrestricted domain

int ranger over 0-1 (same as a mutex)

2 or more processes wait indefinitely for an event that can be caused by 1 of the waiting process

max CPU utilization obtained with multiprogramming

CPU Utilization - keep CPU as busy as possible

Throughput - no. of processes that complete execution per time unit

Turnaround time - amount of time to execute a particular process

Waiting time - amount of time a process has been waiting in the ready queue

Response time - amount of time it takes from a request submission to first response

CPU must check if every memory access generated in user mode to be sure it is between base and limit for that user

An early method that suffers from fragmentation issues where 1/3 may be wasted

Memory management scheme that supports user view of memory

Logical address consists of 2 tuples eg <segmentation no. , offset>

Segment table: maps 2D physical addresses that each have:

base - contains starting physical address where segments reside in memory

limit - specifies length of segment

Physical address space of a process can be noncontiguous

Avoids external fragmentation and avoids problem of varying sized memory chunks

Each file occupies set of contiguous blocks

Each file is in a linked list of blocks

Eachfile has its own index block(s) of pointers to its data blocks

Smallest addressable unit, usually 512B in size

Set of tracks wthich can be accessed without moving arm

connection for device

I/O transfer disk and memory are in units of blocks