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Computers
Operating System Essentials
Operating Systems
PROGRAM
OPERATING SYSTEM
HARDWARE
Operating Components
APPLICATION PROGRAMS
SYSTEM PROGRAMS
(COMPILERS, etc.)
MEMORY
OPERATING SYSTEM
MACHINE LANGUAGE
KERNEL
MICROPROGRAMMING
ROM
PHYSICAL EXECUTION
CPU
System Structure Layers
Processor Hardware functions: circuits,
instruction set, procedures, interrupts
Process management: multiprogramming,
management of secondary storage, logical
addressing
External resource management:
communication among process, file
management, device access and addressing,
user support
OS Functions
User Interface
Resource Management
Evolution
User Interface Functions
Create programs
Execute programs
Access I/O devices
Manage file access
Provide shared access
Manage error detection
Provide accounting
Resource Management
Shares resources among applications
Increases efficiency
Evolution
Support hardware upgrades
Enables operating system upgrades and
additional features
Fixes
Essential OS Functions
Process management
Memory management
Information protection and security
Scheduling and resource management
System architecture
Process
Consists of
Executable program
Data and data resources
Execution context: register contents,
priorities and module status
Process Management
Multiprogramming

Running several programs at a time to increase
cpu utilization
Time sharing

Allowing multiple interactive users to log in at the
same time
Real time transaction processing

Allow multiple users/programs to use the same
copy of a program at once
Batch Multiprogramming (Short
term dispatching)
READY
NEW
RUNNING
WAITING
I/O
HALTED
ERROR/
COMPLETE
Process Control Block (Short
term scheduling)
Block
Identifier
State
Program Counter
Memory Pointers
Context Data
I/O Status
Accounting
Information
Contents
Current process ID
New/Ready/Wait/etc
Address of next instruction
Start and end location of
process in memory
Register contents
I/O requests and assignments
Dispatching: lower level
process scheduling
50 - 60 automatic interrupts per
second
Returns control to the OS for
rescheduling


preemptive scheduling
run to completion
Process Management
Problems
Synchronization: correct management of
interrupted processes
Mutual exclusion: keeping shared resource
use separate
Determinate program operation: programs
get the same result every time independent
of what else is running
Deadlock
Memory Management
Virtual memory and file management
Isolation
Automatic allocation and management
Support modular programming
Protection and access control
Long-term storage
Addresses
Physical address: actual memory location.
NEEDED BY THE CPU
Relative address: offset from a reference
physical address. NEEDED BY THE
OPERATING SYSTEM
Logical address: address within a
programmed unit (e.g. page). NEEDED BY
APPLICATION PROGRAMS
Virtual Memory
PAGE NUMBER +
OFFSET
PAGE
TABLE
FRAME NUMBER +
OFFSET
PAGE
TABLE
PAGE
TABLE
Pages
Page Frames
Page Table Access
A page table is an index to the current
location of a page. Access can be
Swapped
Page Segmentation (hierarchical)
Hashed
Translation Lookaside Buffer :
Page Cache
ALU
CNTL
.....
CACHE
BUS
MAIN MEMORY
TLB
Page Frames
DASD
Pages
Information Protection and
Security
Access control: authorization and
access limitation
Information flow control: manage the
distribution of information to the proper
location
Certification: assure that protection
and security systems are working
correctly
Scheduling and Resource
Management
Considers
Fairness
Differential response
Efficiency
Modern Operating Systems
Microkernel Architecture
Multithreading
Symmetric pultiprocessing
Virtual Machine O/S
Users think they have the entire
machine
Copies of machine can execute the
complete machine language
May run different operating systems in
different partitions
OS Management