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

Activity
Apple, Google, IBM, Intel, Microsoft, Oracle, Samsung, Dell, Acer, Arm, Lenovo, SAS and SAP
Choose three of the above global IT companies and briefly investigate and explain the 
primary expertise that each holds, and the business model (or models) that they use to 
generate revenues and make profits (for example, what they sell and to whom, and how). 

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IS1060 Introduction to information systems
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Use the various company websites as the main basis for your research. In each case just 
add WWW. to the front, and .COM to the back of the name and you will probably find 
them! 
4.2.2 A Simple model of basic computer hardware
Whether a computer is huge and powerful or small and portable, we 
can use the same general logical model to understand its structure. The 
elementary model of a computer is based on four interconnected elements:
• input device
• memory (or storage) 
• central processing unit (CPU)
• output device.
In a small PC or mobile phone, the CPU will consist of a single 
microprocessor fabricated on a silicon chip. Instructions to the computer 
as to what it is to do (the software, a program) as well as data, are entered 
via the input device and stored in the memory. From there, the instructions 
can be fetched and executed by the CPU. Software allows the data stored 
in the memory to be manipulated in various ways, and the results can be 
displayed via the output device.
This simple model needs to be fleshed out a bit in two directions. First, the 
processor can be seen as essentially having to perform two functions: 
• It must understand program instructions so they can be read and 
executed in sequence.
• Based on the program instructions, it must manipulate data items. 
The concept of memory also needs to be explored a little more. It is 
essential to the character of any computer that it is a ‘stored program’ 
device with programs that are stored in memory. The memory that holds 
the current program and the current data needs to be able to deliver 
this to the CPU at great speed. There is in this simple model only one 
CPU and it must not be kept waiting. (In real life, computers big and 
small will often have multiple processors working in parallel and sharing 
access to some common storage.) Some memory – referred to as RAM 
(random access memory) or main memory – is plugged into the body of 
the computer with direct and high speed connection to the CPU. RAM is 
relatively expensive, and the amount of data it can store will be relatively 
small. When you turn off the computer’s power, whatever is stored in RAM 
is lost. Thus, it is said to be volatile storage.
It is fundamental that a computer needs a program to follow in order to do 
anything useful – but there is a chicken and egg problem here. How do the 
instructions get into the memory if the volatile memory (RAM) is empty at 
start up and, hence, the computer has no program to follow to allow it to 
read some stored program from a secondary storage device? In practice, 
you know there must be an answer, because when you switch on your 
computer or phone it does spring into life. That answer is contained in a 
further form of memory – the ROM (read only memory). ROM is another 
form of chip memory, but one that will permanently hold the data that is 
written into it. A computer will have some small program permanently 
stored within itself, a program that is able to initiate the reading of further 
programs from the secondary storage devices (for example, discs on a PC, 
but other, slower chip memory on a phone). This is often referred to as the 
bootstrap ROM, since it ‘pulls the computer up by its bootstraps’. Hence 
the everyday expression to ‘boot’ or ‘reboot’ the computer.

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Chapter 4: Contemporary trends in information and communication technologies
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As the programs that computers execute have increased in size and 
complexity, two new approaches to managing memory have been used. 
Virtual memory uses portions of the secondary memory (e.g. hard disc) 
as if they were parts of the main RAM memory of the computer. Cache 
memory speeds up the process of communicating data to and from a 
secondary storage device, by guessing ahead of time what data is likely to 
be used by the CPU next and fetching it before it is actually requested.
The description here of computer hardware is brief and somewhat 
minimal. This is not, after all, the main focus of this course. However, 
these few basic ideas of how a computer works logically and schematically 
are needed to follow the wider discussions and when we come to discuss 
how computers are used and their consequences in the world.