4. “A collection of independent
computers that appears to its users as
a single coherent system”
5. Distributed Systems
A distributed system organized as middleware. The middleware layer extends over
multiple machines, and offer each application the same interface.
13. Multiprocessor Systems
Continuous need for faster computers
shared memory model
message passing multiprocessor
wide area distributed system
16. File Management vs Database Management (why do we need
database?)
Advantages of Database systems: storage persistence,
programming interface, transaction management
Data Model (What is Data?)
Database Language (How to manipulate data?)
DBMS Architecture and Database System Components (How can
you build a billion-dollar software, like Oracle? Or you can get it
free, mySQL?)
Users classification (What you can do and what you cannot do?)
17. Where are databases?
You cannot avoid it and it’s everywhere!
You can say it actually makes the current society and your life work!
Banking/Credit card /Social Security Info…
Online shopping/booking…
19. OS Structure
monolithic approach
the whole OS is one large program
often used under resource constraints (processing power, memory space)
example: PC DOS
layered approach
functionalities are grouped into layers from hardware to user programs
better separation of functions
example: OS
20. Kernel
core part of the operating system comprising the minimal set of functionalities
process dispatching
basic memory management
interprocess communication
protection
is always kept in main memory
porting is made easier
22. MS-DOS & Windows Structure
originally (DOS 1) monolithic due to space and processing power restrictions (Intel
8086, 8 KBytes main memory)
slow incorporation of advanced concepts
hard disk, hierarchical file systems, I/O redirection, background printing, networking, ...
fresh start with Windows NT
single-user, multitasking
designed for 32-bit microprocessors (Intel Pentium)
23. Windows NT Structure
hardware abstraction layer (HAL)
provides adaptation to the underlying hardware through a generic hardware interface
microkernel
thread scheduling, process switching, exception handling (interrupts), multiprocessor
synchronization
executive services
modules for system functions
I/O manager, object manager, process manager, virtual memory manager, security reference
monitor, windows modules
system services
interface to software running in user mode
24. Windows NT StructureMicrokernel OS
Users and
User Programs
[Stallings 98]
Hardware
Micro-Kernel
System Services
WindowsNT
Executive
Applicationsand
UserInterface
Hardware Abstraction Layer (HAL)
I/O
Manager
Object
Manager
Security
Reference
Monitor
Process
Manager
Local
Procedure
Call
Facility
Virtual
Memory
Manager
Window
Manager
Graphic
Device
Drivers
Device
Drivers
Network
Drivers
File System
Drivers
POSIX
Subsystem
Win32
Subsystem
OS/2
Subsystem
Security
Subsystem
Cache
Manager
25. DESIGN ISSUE
The distributed information system is defined as “a number of interdependent
computers linked by a network for sharing information among them”. A distributed
information system consists of multiple autonomous computers that communicate
or exchange information through a computer network.