Information Technology Reference
In-Depth Information
The DNA nucleotide alphabet consists of four symbols
{
A
,
T
,
C
,
G
}
, while the
RNA nucleotide alphabet is
{
A
,
U
,
C
,
G
}
. The binary alphabet has two symbols. A
bit
, usually denoted by an element of
, is an element of a binary alphabet.
Computer keyboards have around 80 keys. Striking them (one, two, or sometimes
three of them) a character is generated belonging to an alphabet of 128 standard
elements (ASCII characters) plus another 128 characters with specific usages. Any
of these 256 characters can be represented by a sequence of eight binary symbols,
called a
byte
. Table 1.1 collects some important examples of alphabets.
{
0
,
1
}
Ta b l e 1 . 1
Important alphabets
Binary Alphabet
{
0
,
1
}
Number Decimal Alphabet
{
0
,
1
,...,
9
}
DNA Alphabet
{
A
,
T
,
C
,
G
}
Archaic Latin Alphabet 21 letters
Amino acids Alphabet 21 letters (including stop symbol)
Chemistry Alphabet Around 100 symbols
Minimal Computer Keyboard Alphabet Around 80 characters (text + control)
A definition of life is even more difficult than that a definition of information.
Life, in a full sense, includes at least seven essential features: i)
birth
, ii)
nutrition
(feeding resources from the environment, expelling degraded sub-
stances), iii)
growth
,iv)
interaction
(with stimuli from/to the environment),
v)
reproduction
,vi)
death
, and vii)
evolution
.
The first five features refer to the individual living organisms, seen as particular
instances of life, in time and space. The last two features refer to populations of
living organisms instantiating forms of life, which by means of their cycles of birth-
reproduction-death realize a second level dynamics, providing, along the arrow of
time, a
tree of life
, that is, a “genealogy” of life
species
(at least one individual must
reproduce for the survival of the population and all individuals eventually die).
Life exhibits a tremendous complexity of interacting processes which, at dif-
ferent levels, have to communicate for reaching successful realizations of specific
functionalities. The complexity of this underlying dynamics needs information.
Life emerged only when an efficient system of data processing was possible
at molecular level.
In fact, the fundamental discovery of the past century was the molecular struc-
tures and processes which life is based on. Molecules are discrete structures built on
atoms.
