Introduction to information systems T. Cornford, M. Shaikh is1 060 2013

Cloud computing
: In the wider world beyond science and engineering, 
a similar idea to a GRID is today at the forefront of computing and the 
development of new information systems – called cloud computing. In 
this case, a large network of computing resources (processors and storage 
devices) is made available for multiple users to use by the minute or by 
the kilobyte of data – just as you pay for phone calls by the second or 
electricity by the kilowatt. Thus it is possible for a business organisation 
to ‘rent’ processing power and data storage capacity on an as-needed 
basis from a supplier of such services. There may be no need to build and 
manage a data centre of your own. Two well-known companies that offer 
such services for business users are Amazon and Microsoft, and they have 
many clients both big and small. Using the cloud (a public ‘for rent’ cloud) 
just to obtain processing power and storage (infrastructure in the jargon 
– hence Infrastructure as a Service or IaaS), or it may be to also rent the 
use of software or a specific service – called Software as a Service or SaaS 
(see Laudon and Laudon (2013), Sections 5.3 and 5.4). Individual people 
too may rent storage capacity and software services; for example, in photo 
sharing sites such as Picasa or general file sharing sites such as DropBox 
(www.picasa.com; www.dropbox.com). Another example of cloud services 
for providing software include Google Apps: www.google.com/apps/

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Chapter 4: Contemporary trends in information and communication technologies
51
4.2.4 Client server computing
As noted above, today all computers are usually connected to 
networks
, 
and thus we can also describe them by their role within the network. 
It is usual to identify two roles – that of a