Computer
Architecture
Operating
Systems
Presented By:
1.Randunu Dimeshan (CL/HDCSE/96/02)
2.Ravishankar Thanushan (CL/HDCSE/96/37)
3.Mohamed Shamil (CL/HDCSE/96/21)
4.Madusha Alawattegama (CL/HDCSE/96/11)
• 1. Operating Systems
1.1 What is an operating system
1.2 Different types of operating systems
• 2. Features in Operating Systems
2.1 The Interrupt
2.2 Virtual Memory
2.3 Direct Memory Access
• 3. Functions in Operating Systems
Table of Content
3.1 Memory management
3.2 File management
3.3 Control over system performance
• 4. Advantages of a microprocessor system
• 5. Operating System related terms
5.1 Kernel
5.2 Scheduler
• 6. References
1.Operating System
1.1 What is an Operating System
An operating system is a software installed on a computer's hard drive that
enables the computer hardware to communicate and operate with the
computer software. The software which acts as an interface between the end
user and computer hardware.
(Computer Hope, 2021)
Ex-
Windows
MAC
Linux
Ubuntu
1.2 Different
Types of
Operating
System
1)
2)
3)
4)
5)
6)
7)
Batch Operating System
Multitasking/Time Sharing OS
Multiprocessing OS
Real Time OS
Distributed OS
Network OS
Mobile OS
1.2.1 Batch Operating System
Some computer processes are very lengthy and time-consuming. To speed
the same process, a job with a similar type of needs are batched together
and run as a group.
(Guru99, 2021)
OS loaded and executed programs in tape one at a time.At the end of entire
batch of programs, output tape was printed with an inexpensive machine.
EgPayroll system
Bank statements
Advantages
multiple users can share
the batch system.
The idle time for the
batch is very less.
It's easy to manage
large group of batch
system.
1.2.2 Multitasking/Time
Sharing OS
The operating system which allows to run multiple tasks
simultaneously. The processor time (CPU) which is shared
among multiple users is termed as time sharing. (Guru99,
2021)
The main objective is to minimize response time.
ExWindows
MAC
Linux
Ubuntu
Advantages
❖ A computer user can save his time.
❖ Better program error endling.
❖ Better usage of resource and save idle
time.
1.2.3
Multiprocessing
OS
Usage of two or more central processing units
parallelly within a single computer system. and
sharing relevant resources to gather. A
multiprocessing operating system is capable of
running Lot of programs at the same time. most of the
modern operating systems support multiprocessing.
(computer notes, 2021)
ex:Windows
Linux
Mac OS
Unix
Advantages
COST EFFECTIVE SYSTEM.
PARALLEL PROCESSING
SYSTEM.
HIGH RELIABILITY.
1.2.4 Real Time OS
Advantages
Error free on task handling.
Focus on given application.
Best memory allocation.
1.2.5
Distributed
OS
Distributed operating system allows distributing of
entire systems on the couples of Center
processors, and it can be access by multiple user.
processors in this system vary in size and its
functions too, they are referred as nodes, sites,
computers.
(GeekforGeeks, 2019)
ExLOCUS
Micros
IRIX
Advantages
Better service to the customer.
Speed in exchange process.
Easy to share resources.
The software which allows multiple devices within a network
to communicate and share resources with each other.
1.2.6
Network OS
These systems run on a server and provide the capability to
manage data, user, groups, security, application, and other
networking functions too.
(GeekforGeeks, 2019)
EgMicrosoft Windows Server 2012
Mac os X
Linux
Advantages
Easy to access new resources.
Server easily accessible
through virtually .
Provide best security to entire
setup.
1.2.7 Mobile OS
Mobile OS present as a graphical display of buttons, icons, windows, and tiles that you can touch or interact
with to perform various tasks. All hardware components are packed to one tiny circuit.
The operating system which is designed to power mobile, Tablets and Wearables platforms. (Dotdash, 2020)
Ex-
Android
Ios
Blackberry OS
Advantages
user friendly os.
easy to customize.
run many apps at the
same time like Computers.
What is Von Neumann Architecture
2. Features of
Operating
System
The Von Neumann architecture used to be an individual point of shared
memory required by the software applications and its data processing
operations. The Von Neumann processing is a single bus used for
accessing the memory and also an unit of arithmetic. It also known as
program control unit. The fetching and executing cycle will be seriously
executed by the Von Neumann processors.
Architecture Techniques
1.
2.
3.
The Interrupt
Virtual Memory
Direct Memory Access (DMA)
2.1 The
Interrupt
This is a mechanism used for which, the memory or modules
such as I/O may get interrupted. Basically, Interrupts are
known also as the processor’s response to a particular
software application running on the machine. An interrupt
will alert the processors as requests for the processors to
interrupt the currently executing application whenever
required. In that case the particular running event can be
processed or executed in timely manner. Basically, when a
program stops responding, the thread will have to
continuously have to be focused on this particular application.
And this will consume more memory and processing
resources as well.
So, this is where the Interrupts come in to the play. The interrupts will
sense the signal and accordingly the computer will be turned to either to
continue with the running program or to terminate it or to run a new task.
Today, all the modern computers are interrupt-driven computers. Usually,
computers can perform only one task at a time, but just because of these
can be interrupted, it could take turns and run. This is known as
multitasking. Multiple tasks or instructions being ran at once.
The operating systems uses interrupt-handler events to manage the
interrupts. The interrupt handlers will prioritize the and process the
interrupts in a queue.
Virtual memories are a set of volatile memory which will be created in
the hard drive of a computer. This is usually used when the RAM of the
computer is lesser. In other words, if a computer needs memory power,
more than what it already has, then without installing a physical /
hardware RAM (memory), this option can be enabled.
2.2 Virtual
Memory
If this function is activated in the operating system, then the hard disk
space, from the location which we have specified, a slot of memory will
be locked and will be used for system processing memory power. For
example, if the computer only has 4Gb of a RAM, then by turning on
this feature a virtual memory of 16Gb could be allocated, so, this 16Gb
space will be locked in the hard drive. This way the computer
performance can be increased.
2.3 Direct
Memory
Access
(DMA)
Without the participation of the processor, DMA (Direct Memory
Access) will transfer the data across the memory and the
connected devices in the computer. The unit which controls and
handles the activities of accessing memory direct is known as
Direct Memory Access (DMA).
For few clock cycles, the processor will be relinquished the
system bus. Because of this DMA can achieve the operation of
the data transferring through the system bus. CPU will receive a
HOLD request also known as HLD, from the DMA, and
renounces bus and then sends the HOLD acknowledgement, also
known as HLDA to the DMA. Once the HLDA has been
received, the DMA will acknowledge the connected I/O device
and the transferring process of the data can be accomplished,
hereafter the DMA will take control of the system bus and the
transfer data from the memory or to the memory.
As soon as the the data transferring task is done, then the
DMA will trigger an Interrupt to make the processor aware
about the completion of the data transfer, afterwards the
processor will take charge over the bus once again.
3. Functions in
Operating
Systems
3.1 Memory Management
Memory management is the process of
an OS that manages the memory
allocation in the primary memory of a
computer and moving the computing
processes between the main memory
and secondary/storage
memory. (Tutorialspoint.com, 2020)
Single contiguous Allocation- most straightforward technique is
available. The entire available memory, except a small portion reserved
for the OS functionality, will be assigned for one program. MS-DOS is an
example.
Partitioned Allocation- this divides the primary memory into partitioned
memory blocks, each block containing all the instructions to run a specific
task or a job.
Memory
management
techniques
Paged Memory Management-this This divides the memory into fixedsize units called page frames. The pages belonging to a given process
are placed into available memory frames.
Segmented Memory Management- this breaks the virtual address of a
single process into segments, which gets placed in non-linear and noncontiguous areas of physical memory.
A file management system is a system that maintains files on a
computer. An example of a file management system is Windows
Explorer in Windows OS. It can perform tasks such as file creation,
modification, file detail, ownership management, and deletion.
Furthermore, it helps with sharing the files between users, storing
them in directories, and queuing them for processing. (Shukla, 2017)
A file management system is based on a few concepts.
3.2 File
Management
1.File Attributes- this specifies a file's characteristics, such as the
date it was created, the disk's location, the date it got modified, etc. It
helps the user to locate the file and understand the value it.
2. File operation - Tasks such as opening a file or closing a file.
3. File access permission- It manages the licenses such as read and
writes.
4.File systems- it specifies the method of file storage in a computer
drive such as NTFS or FAT32.
3.3 Control over
system
performance
4. Advantages of a
microprocessor system
A microprocessor is a logical processor in a
silicon chip embedded with a Central
Processing Unit (CPU). It is the main
component of a computer system—this what
brings your computer into life when you turn it
on. A microprocessor handles all the arithmetic
and logic operations of a computer system. Its
main work is taking some input data and
instructions, process the data as per the
instructions, and output the data.
Figure 4: A microprocessor system
There are many advantages to a microprocessor system.
•
Speed: They can process data faster than any human could. The rate is calculated
with Hertz. Most modern processors operate around 3.7Ghz, and an overclocked
gaming microprocessor can safely achieve speeds up to 5Ghz. That is five billion
calculations per second.
•
Multitasking: The type of multitasking used by the microprocessors today is called
pre-emptive multitasking. It works by interrupting each program and passing control
onto another one. Due to the speeds mentioned above, they can swap between the
tasks and operations faster. There are multiple-core microprocessors in the market,
which makes this task-swapping process faster.
•
Efficiency and Reliability: Microprocessor systems can run nonstop 24/7 and even
work in conditions that a human would not be able to. And the outputs are consistent
and error-free.
•
Compact: Modern microprocessor systems are relatively small, making the
computing systems even smaller.
5. Operating System Related Terms
Kernel
Scheduler
5.1 Kernel
Every operating system has a core program called “Kernel” which is the most
important part of the OS.
Anything that happens on the computer has to go through it to function properly.
Kernel loads first into memory when an operating system is loaded and remains in
the memory until operating system is shut down again.
The Kernel acts as a translator between software and hardware, it translates the
input/output requests from software into an instructions set for the CPU and GPU
Basic Kernel Structure
Kernel is simply a layer
between
software and hardware which
makes everything possible
Functions of a Kernel
These are the main functions which the Kernel performs
1. Process management - The creation, execution, and termination of processes keep on
going inside the system whenever a system is in the ON mode.
2. Memory Management - The kernel keeps track of the used memory and allocates the
remaining memory to the other processes.
3. Device Management - Every component connected to the system including I/O devices
are managed by the kernel.
4. Interrupt Handling - The kernel will interrupt an ongoing task if another task with higher
priority should be executed at that exact moment.
5. I/O communication - The kernel handles all the information entered by the user and all
the information provided to the user by the system.
5.2 Scheduler
•
Schedulers in Operating Systems are the process which
decide which task should run at a given time.
•
They are vital in maintaining highest possible system
performance and is crucial in maintaining the multi tasking
abilities of a computer.
•
They are algorithms in the operating system with the
purpose of optimizing the system to get the maximum
performance.
They are algorithms in the operating system with the
purpose of optimising the system to get the maximum
performance.
Basic
structure of
a Scheduler
There are 3 main types of Schedulers
Types of
Schedulers in
an OS
1.
Long term scheduler - Long term schedulers run less frequently,
and their job is to decide which program gets into the job queue.
2.
Short term scheduler - Short term schedulers run more frequently,
and they are also called CPU schedulers. Their main goal is to
improve CPU performance and process execution rate.
3.
Medium term scheduler - Medium term schedulers carry out a
process called “swapping”. They remove a program from the
memory and then reintroduce it to the memory to be continued
from where it was left off. This process is important when
memory needs to be freed up due to a change in memory
requirements.
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