2. OPERATING SYSTEM
Program that acts as an intermediary/interface between a user of a computer and
the computer hardware
It provides a user-friendly environment in which a user may easily develop and
execute programs
Otherwise, hardware knowledge would be mandatory for computer programming.
3. OPERATING SYSTEM
Operating system goals:
Execute programs and solve user problems
easily
Make the computer system convenient to
use
manner
Manage all hardware and software
Controls every file, device, section of main
memory and nanosecond of processing time
Controls who can use the system
4. • When you turn on the computer, the CPU automatically begins executing instructions
stored in ROM.
• The operating system (OS) loads from the disk into part of the system’s memory.
• OS loads the application program into memory and remains in memory, So that, it can
provide services to the application program—display on-screen menus, communicate
OPERATING SYSTEM
5. WHAT DOES AN OPERATING
SYSTEM DO?
Every computer depends on an operating system to:
Keep hardware running efficiently
Maintains file system
Support multitasking
Manage virtual memory
Operating system runs continuously when computer is on….
6. FUNCTIONS OF AN OPERATING
SYSTEM
Includes five essential subsystem managers
Memory Manager
Processor Manager
Device Manager
File Manager
Network Manager
7. MAIN MEMORY MANAGEMENT
In charge of main memory
Random Access Memory (RAM)
Responsibilities include:
Preserving space in main memory occupied by
operating system
Checking validity and legality of memory space
request
Setting up memory tracking table
Tracks usage of memory by sections
Needed in multiuser environment
De-allocating memory to reclaim it
8. PROCESSOR MANAGEMENT
In charge of allocating (CPU)
Tracks process status
An instance of program execution
Two levels of responsibility:
Handle jobs as they enter the system
Handled by Job Scheduler
Manage each process within those jobs
Handled by Process Scheduler
9. DEVICE MANAGEMENT
In charge of monitoring all resources
Devices, channels, and control units
Responsibilities include:
Choosing most efficient resource allocation
method
Printers, ports, disk drives, etc.
Based on scheduling policy
Allocating the device
Starting device operation
Deallocating the device
10. FILE MANAGEMENT
In charge of tracking every file in the system
Data files, program files, compilers, application
programs
Responsibilities include:
Enforcing user/program resource access
restrictions
Uses predetermined access policies
Controlling user/program modification
restrictions
Read-only, read-write, create, delete
Allocating resource
Opening the file
De-allocating file (by closing it)
11. NETWORK MANAGER
In all modern operating systems
Assumes responsibility for networking tasks
Convenient way for users to share resources
Retains user access control
Resources include:
Hardware (CPUs, memory areas, printers, tape
drives, modems, and disk drives)
Software (compilers, application programs, and
data files)
12. FUNCTIONS OF AN OPERATING
SYSTEM
Each manager:
Works closely with other managers
Performs a unique role
Manager task
Monitor its resources continuously
Enforce policies determining:
Who gets what, when, and how much
Allocate the resource (when
appropriate)
De-allocate the resource (when
appropriate)
14. HISTORICAL DEVELOPMENT OF OS
Upto year 1955
Computers based on vacuum tube
technology
No standard operating system software
Poor machine utilization
From 1956- 1963
I/O device speed gradually became faster
Records blocked before retrieval or storage
Access methods developed
Buffer between I/O and CPU introduced & Reduced speed
discrepancy
15. HISTORICAL DEVELOPMENT OF OS
TILL 1970
Faster CPUs Speed caused problems with slower I/O devices
Multiprogramming schemes used to reduce speed discrepancy with CPU
Main memory physical capacity limitations
Virtual memory developed to solve physical limitation
Database management software was developed
A number of query systems introduced
Programs started using English-like words, modular structures, and standard
16. HISTORICAL DEVELOPMENT OF OS
From 1971 to 1980
Cost/performance ratio of computer
components
More flexible hardware (firmware)
Multiprocessing
Allowed parallel program execution
Evolution of personal computers
Upto 1990
Demand for Internet capability
Sparked production of networking capability
Increased networking
Tighter security demands to protect hardware and
software
Multimedia applications
Demanding additional power, flexibility, and device
compatibility for most operating systems
17. FROM 1990 TILL PRESENT
Primary design features support:
Multimedia applications
Internet and Web access
Client/server computing
Evolution of high-speed communications
Distributed processing and networked systems introduced
Computer systems requirements
Increased CPU speed
High-speed network attachments
Increased number and variety of storage devices
Virtualization
19. EVOLUTION OF OPERATING SYSTEM
The evolution of operating systems went through seven major phases.
Each of them significantly changed the ways in which users accessed computers
through the open shop, batch processing, multiprogramming, timesharing,
concurrent programming, personal computing, and distributed systems.
20. EVOLUTION OF OPERATING SYSTEM
Major Phases Technical Innovations
Open Shop The idea of OS
Batch Processing Tape batching,
First-in, first-out scheduling.
Multi-programming Processor multiplexing, Indivisible operations, Demand paging, Input/output spooling, Priority scheduling,
Remote job entry
Timesharing Simultaneous user interaction,
On-line file systems
Concurrent Programming Hierarchical systems, Extensible kernels, Parallel programming concepts, Secure parallel languages
Personal Computing Graphic user interfaces
Distributed Systems Remote servers
22. OPERATING SYSTEM TYPES
Five categories
Batch
Interactive
Real-time
Hybrid
Embedded
Two distinguishing features
Response time
How data enters into the system
23. BATCH SYSTEMS & INTERACTIVE
SYSTEMS
Batch Systems
Input relied on punched cards or tape
Efficiency measured in throughput
Faster turnaround than batch systems
Slower than real-time systems
Introduced to provide fast turnaround when
debugging programs
Time-sharing software developed for operating
system
24. REAL-TIME SYSTEMS
Reliability is key
Fast and time limit sensitive
Used in time-critical environments
Space flights, airport traffic control, high-speed aircraft
Industrial processes
Distribution of electricity
Telephone switching
Must be 100% responsive, 100% of the time
25. HYBRID & EMBEDDED SYSTEMS
Hybrid systems
Combination of batch and interactive
Accept and run batch programs in the
background
Interactive load is light
Embedded systems
Computers placed inside other products
Adds features and capabilities
Operating system requirements
Perform specific set of programs
Not interchangeable among systems
