APPENDIX 8: ABBREVIATIONS AND GLOSSARY
3G  Third generation

ALU  Arithmetic logic unit 
BCS  British Computer Society

CITRIS  Centre for IT Research in the Interest of Society, University of California

CMOS  Complementary MetalOxideSemiconductor

CPU  Central processor unit

CRT  Cathode ray tube 
CS  Computer Science 
bn  billion 
DTI  Department of Trade and Industry

DSP  Digital Signal Processor

EPSRC  Engineering and Physical Sciences Research Council

EU  European Union 
EUV  Extreme ultraviolet 
FET  Fieldeffect transistor

GDP  Gross Domestic Product

GSM  Global System for Mobile communications

HEFCE  Higher Education Funding Council for England

ICT  Information and communication technology

IEE  Institution of Electrical Engineering

IMEC  InterUniversity Microelectronics Centre, Belgium

IP  Intellectual property 
IRC  Interdisciplinary Research Collaboration

ISLI  Institute for System Level Integration, Livingston

IT  Information Technology 
IT&CS  Information Technology and Computer Science

ITRS  International Technology Roadmap for Semiconductors

LCD  Liquid crystal display

mm  millimetre 
nm  nanometre 
NHS  National Health Service

NPL  National Physical Laboratory

OECD  Organisation for Economic Cooperation and Development

OMI  Open Microprocessor Systems Initiative

p  page number in the accompanying volume of evidence

PC  Personal computer 
PDA  Personal digital assistant

PPARC  Particle Physics and Astronomy Research Council

Q  question number in the accompanying volume of evidence

qubit  quantum bit 
R&D  Research and development

RAE  Research Assessment Exercise

RISC  Reduced instruction set computing

SETI  The Search for Extraterrestrial Intelligence project

SLI  System level integration

SoC  SystemonChip 
UK  United Kingdom 
US  United States of America

UV  Ultraviolet 
Very large and very small numbers
1. Modern computer technology involves both very large and
very small numbers. To avoid long names or large numbers of decimal
places, these are normally indicated by use of standard prefixes.
For example, a millionth of a second is referred to as a microsecond
and a millionth of a metre is a micrometre (also sometimes referred
to as a micron).
2. These prefixes cover the very large to the very small as
in the following table. The difference between each step is a
factor of a thousand.
Prefix  Symbol
 Quantity  Number
 Notation 
Tera  T
 million million
 1000000000000  10^{12}

Giga  G
 thousand million
 1000000000  10^{9}

Mega  M
 million
 1000000  10^{6}

Kilo  k
 thousand
 1000  10^{3}


 one 
1 

Milli  m
 thousandth
 0.001  10^{3}

Micro  µ
 millionth
 0.000001  10^{6}

Nano  n
 thousand millionth
 0.000000001  10^{9}

Pico  p
 million millionth
 0.000000000001  10^{12}

Femto  f
 thousand million millionth
 0.000000000000001  10^{15}

3. It is obviously easier to say "3 gigahertz" (a
measure of computer speed) than "three thousand million hertz".
For calculations and some other purposes, however, it is necessary
to write down the numbers. If written in full, 3 gigahertz would
be 3,000,000,000 hertz. However, the conventional way of writing
such a large number is 3 x 10^{9}, being three multiplied
by 10 to the power 9 (10 multiplied by itself nine times) or a
thousand million.
4. Such power notation is also used to simplify very small
numbers. A minus power represents one divided by the number that
would be generated by that power if positive. For example, 10^{9}
(referred to as "10 to the minus 9") is one divided
by 10^{9} or one thousand millionth. 5 nanometres (being
five thousand millionths of a metre or 0.000000005 metres) may
thus be written as 5 x 10^{9} metres.
Dimensions
5. Individual elements on a modern computer chip are best
measured in nanometres (nm), of which there are one thousand million
to the metre, the standard metric unit of length. (The now lessused
Ångström unit is one tenth of a nanometre.)
6. To illustrate such very small distances, a ream (500 sheets)
of standard paper is 50 millimetres thick. 10 sheets are thus
a millimetre and a single sheet is 100 micrometres thick. A nanometre
is one thousandth of a micrometre. If it were possible to make
paper only one nanometre thick, it would take one hundred thousand
sheets (200 reams) to equal the thickness of one sheet of ordinary
paper.
7. Computer chips are manufactured in layers, some of which
are only 1.5 nm thick. Atoms in a silicon crystal are about a
fifth of a nanometre apart, so such layers are only 7 or 8 atoms
thick. Critical horizontal measurements can be as small as 5 nm
or 25 atoms.
Speed
8. A computer's actions are synchronised by highfrequency
pulses from its clock. The standard measurement of frequency is
the hertz, being one event per second. Modern PCs operate at clock
rates in the gigahertz range, that is at over a thousand million
(10^{9}) cycles per second. To say that a computer works
at 1 gigahertz is exactly the same as saying that it completes
each event in 1 nanosecond (10^{9} seconds).
9. Each step of a computer's operation is one of those events.
However, delivering a program instruction (for example, retrieving
data, processing it and storing the result) involves several steps.
A measure of a computer's operating speed is the millions of instructions
per second (MIPS) with which it can deal.
10. Calculations involving fractions are more complicated
than dealing with integers. For some applications, users need
to know a computer's speed in handling floating point operations
per second (FLOPS).
11. Early computers completed each operation before turning
to the next so their speed in MIPS was always less than their
clock rate. Modern machines not only handle a number of instructions
in parallel but also begin the next batch of instructions before
the previous batch is finished. Their speed in MIPS or FLOPS can
thus exceed their clock rates.
Storage capacity
12. The basic unit of computer data is a binary bit —
which will have the value of either one or zero. (What a bit represents
is dictated by its context.)
13. A block of 8 bits is called a byte. Modern computers handle
"words" of 32 or 64 bits simultaneously.
14. Computers' data storage capacity is now normally measured
in megabytes and gigabytes — and even in terabytes.
