Aula 3 14032013 sii-v1

Sistemas de Informação
para a Indústria

Class 3

Architectures of IS
Ano 2013

António Grilo
Prof. Auxiliar FCT-UNL

Sistemas de Informação para Indústria 1
Departamento de Engenharia Mecânica e Industrial © António Grilo 2013

BIT AND BYTE

Bit - Binary digit, represents smallest unit of data in the form of either 0 or 1. A bit
(a contraction of binary digit) is the basic unit of information in computing and
telecommunications; it is the amount of information stored by a digital device or
other physical system that exists in one of two possible distinct states. Bits can be
implemented in many forms. In most modern computing devices, a bit is usually
represented by an electrical voltage or current pulse, or by the electrical state of a
flip-flop circuit.

Byte - String of bits, usually eight, stores one number or character. The byte is a
unit of digital information in computing and telecommunications that most
commonly consists of eight bits. Historically, a byte was the number of bits used to
encode a single character of text in a computer and for this reason it is the basic
addressable element in many computer architectures. The size of the byte has
historically been hardware dependent and no definitive standards existed that
mandated the size. The de facto standard of eight bits is a convenient power of
two permitting the values 0 through 255 for one byte. The popularity of major
commercial computing architectures have aided in the ubiquitous acceptance of
the 8-bit size

BIT AND BYTE


INFORMATION TECHNOLOGY (IT) INFRASTRUCTURE
Integrated framework upon which digital networks operate. This
infrastructure includes data centers, computers, computer networks,
Database Management devices, and a regulatory system.

Evolution of IT infrastructure:

General-purpose mainframe & minicomputer era:
• 1959 to present
- 1958 IBM first mainframes introduced
- 1965 Less expensive DEC minicomputers introduced

Personal computer era: 1981 to present:
- 1981 Introduction of IBM PC
- Proliferation in 80s, 90s resulted in growth of personal software


INFORMATION TECHNOLOGY (IT) INFRASTRUCTURE
Client/server era: 1983 to present:
- Desktop clients networked to servers, with processing work split
between clients and servers
- Network may be two-tiered or multitiered (N-tiered)
- Various types of servers (network, application, Web)

Enterprise computing era: 1992 to present:
- Move toward integrating disparate networks, applications using Internet
standards and enterprise application

Cloud Computing: 2008 to present
- Refers to a model of computing where firms and individuals obtain
computing power and software applications over the Internet or other
network
- Fastest growing form of computing

TECHNOLOGY DRIVERS OF INFRASTRUCTURE EVOLUTION
Moore’s law and microprocessing power - Computing power doubles
every 18 months. Since the first magnetic storage device was used in
1955, the cost of storing a kilobyte of data has fallen exponentially,
doubling the amount of digital storage for each dollar expended every 15
months, on average..

Metcalfe’s Law and network economics - Value or power of a network
grows exponentially as a function of the number of network members. As
network members increase, more people want to use it (demand for
network access increases). Declining communication costs (towards 0)
and the Internet, with an estimated 1.5 billion people worldwide have
Internet access.

Standards and network effects - Specifications that establish the
compatibility of products and the ability to communicate in a network
unleash powerful economies of scale and result in price declines as
manufacturers focus on the products built to a single standard.

IT INFRASTRUCTURE HAS 7 MAIN COMPONENTS

• Computer hardware platforms

• Operating system platforms

• Enterprise business applications

• Data management and storage

• Networking/telecommunications platforms

• Internet platforms

• Consulting system integration services


COMPONENTS OF A COMPUTER NETWORK

Two or more connected computers. Major components in simple network:

• Client computer

• Server computer

• Network interfaces (NICs)

• Connection medium

• Network operating system

• Hub or switch

• Router

DIGITAL NETWORKS


CLIENT/SERVER COMPUTING
The client–server model is a computing model that acts as distributed
application which partitions tasks or workloads between the providers of a
resource or service, called servers, and service requesters, called clients.
Often clients and servers communicate over a computer network on
separate hardware, but both client and server may reside in the same
system. A server machine is a host that is running one or more server
programs which share their resources with clients. A client does not share
any of its resources, but requests a server's content or service function.


PACKET SWITCHING
Method of slicing digital messages into parcels (packets), sending packets
along different communication paths as they become available, and then
reassembling packets at destination. Previous circuit-switched networks
required assembly of complete point-to-point circuit. Packet switching is
more efficient use of network’s communications capacity.


TRANSMISSION CONTROL PROTOCOL / INTERNET PROTOCOL (TCP/IP)

Connectivity between computers enabled by protocols. Protocols are rules
that govern transmission of information between two points. It has four
layers:

- Application layer

- Transport layer

- Internet layer

- Network interface layer


TYPES OF NETWORKS

Local-area networks (LANs)

- Client/server or peer-to-peer

- Ethernet – physical network standard

- Topologies: star, bus, ring

Campus-area networks (CANs)

Wide-area networks (WANs)

Metropolitan-area networks (MANs)


NETWORKS

Physical transmission media:

- Twisted wire (modems)
- Coaxial cable
- Fiber optics and optical networks

Wireless transmission media and devices:

- Microwave
- Satellites
- Cellular telephones


PROPRIETARY SOFTWARE VS OPEN SOURCE
Proprietary software is software developed by a supplier and made
available for you to use under an end-user licence agreement (EULA),
which you effectively accept when you install the software. The licence
sets out how the software can be used and usually prohibits you from
doing certain things, like making copies of the software and passing them
on; or selling your licence to someone else.

Most proprietary software comes without the source code. This is the code
originally written by the programmer. Without this code neither you nor any
other software supplier can make changes to the software package.

When you buy a proprietary software package you are not buying the
software - you are buying the right to use the software in a specific way.
The software company owns the software.

Most off-the-shelf packages are proprietary software.

PROPRIETARY SOFTWARE VS OPEN SOURCE

Open source software is made available under a licence that allows you to
make copies and pass them on to anyone. The software comes with its
source code - which you can change to meet your needs.

Licences for open source software do vary. Some licences require to make
any changes made to the source code publicly available, while others will
allow to keep those changes private. The licence agreement shhould be
read before using or changing the software.

Open source software is usually available for free download or off-the-
shelf at a low cost.


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