Crash Course Computer Science Fundamentals

The science is typically
cumulative, i.e. build up more powerful
tools to perform more accurate measurements, need better and are
extended concepts of theory and so on. While paradigms can change, research
usually evolves based on past performance, which constitutes the
foundation for further development. The scientist will be safer
in their research and more prepared for new challenges if
you know how your particular issue has evolved historically,
what the greatest difficulties, the solutions
and the outstanding problems. In the more traditional sciences Philosophy, Mathematics,
Physics, Biology, etc. There is always studies history along with
much other dedicated to thinkers, inventors and conquerors first, second or third
magnitude, as well as numerous monographs. In the case of computing, it is
necessary to appear works as the basis and reference for students,
new researchers and those interested in the theoretical aspects
that are behind this technology that dominates daily life this
weekend and early millennia. The Computer History is marked
by sudden interruptions by unexpected and
unforeseen changes, making it difficult to view the
evolution of computers by a simple linear list of
inventions-names-dates. The desire to know the
links that the work of individual men settled
in time is accompanied by the urge to understand
the weight of these acts throughout the
History of Computing. Seek an understanding of the facts through
the events that preceded it is one of the primary objectives that will be present
in this study the History of Computing. Computer science is a body of knowledge
consisting of a conceptual infrastructure and technological building where to
materialize the hardware and software. The first founded the second and preceded. The theory of computation
has its independent development, in large
part, technology. This theory is based on the definition
and construction of abstract machines, and power of the study of
these machines in troubleshooting. Men through the ages, have
sought to develop effective methods for solving different
types of problems. The constant concern to minimize
repetitive and tedious effort produced the development of machines that began
to replace men in certain tasks. Among these is the computer,
which has expanded rapidly filled and modern spaces
in which people circulate. From the appearance of the notion of
natural number, through arithmetical notation and the more bound notation
to algebraic calculation, it is shown as they appeared fixed rules
that allowed computing quickly and accurately, saving, as he said Leibniz,
the spirit, and the imagination. “Descartes believed in the
systematic use of algebra as a powerful and universal
method to solve all problems. This belief has joined the
other and is the first ideas on universal machines, able
to solve all the problems. It was a powerful belief
mind who left respectable works in mathematics and
sciences in general.” Alan Mathison Turing:
the cradle of Computing The computer revolution began
effectively to be held in 1935, on a summer afternoon in England, when
Alan Mathison Turing (1912-1954), a student of King’s College,
Cambridge, during a course taught by mathematician Max Neumann,
took note of Hilbert. Meanwhile, as was briefly mentioned
in the previous item, a part of the mathematical community was
seeking a new kind of logical calculus, which could, among
other things, put in a sustained mathematical basis heuristic concept
that is to carry out a calculation. The result of this research was fundamental
to the development of mathematics: it was whether it is possible to
have an efficient procedure to solve all the problems of a particular
class that was well defined. All these efforts eventually
form the theoretical foundation of what came to be called
“Computer Science.” The results of Gödel and Turing
motivated decision problem first try to characterize exactly which
functions are capable of being computed. In 1936, Turing was acclaimed as
one of the greatest mathematicians of his time, when he foresee
his colleagues that you can perform computational operations
on the theory of numbers through a machine that has built
the rules of a formal system. Turing defined a theoretical
machine that has become a key concept within the
Theory of Computation. He emphasized from the
beginning that such mechanisms could be built, and its
discovery is just opening a new perspective to the effort to
formalize mathematics, and at the same time strongly marked
the History of Computing. The genial perception of Turing was
the replacement of the intuitive notion of an effective procedure
for a formal idea, mathematics. The result was the
construction of a mathematical concept of algorithm notion,
a notion that he modeled building on the steps that
a human being is when performing a particular
calculation or computation. It formalized the concept of algorithm. The Turing Machine One of the first models of the
abstract machine was Turing machine. As Turing himself wrote: “Computing is written symbols on paper. Assume that the paper
is a grid, the flatness can be ignored, and
it is not essential. Suppose the number of symbols is finite. The computer behavior is
determined by the symbols which he notes at one point, and his
mental state at that time. Suppose there is a maximum
number of symbols or squares that he can
watch every moment. To observe more successive
operations are required. Let us assume a finite
number of mental states. Let’s imagine that the actions
taken by the computer will be divided into such elementary
operations that are indivisible. Each action consists of changing
the computer system and paper. The state of the system is
given by the symbols on paper, the symbols observed by the
computer and your mental state. Every operation, no more than a symbol is
changed, and only the observed change. Besides changing symbols,
operations must change the focus of observation,
and it is reasonable that this change should be made for symbols
located at a fixed distance of the above. Some of these operations
involve mental state changes the computer and then determine
what the next action. ” Turing’s work was documented in
On Computable Numbers with an application to the Entscheidungsproblem,
published in 1936. He described in mathematically
precise terms how powerful it can be an automatic formal system with
very simple rules of operation. Turing determined that
mental calculations consist of operations to transform
numbers into a series of intermediate states progressing
from one to another according to a fixed set of
rules until an answer is found. Sometimes it is using paper and pencil, not
to lose the status of our calculations. The mathematics rules require stricter
definitions than those described in metaphysical discussions about the
states of the human mind, and he focused on the definition of these states so
that they were clear and unambiguous, that such definitions could be used
to command the machine operations. Turing began with a
precise description of a formal system in the form
of “instructions table” that specify the moves
to be made for any possible configuration
of states in the system. Then proved that the steps
of a formal axiomatic system similar to logic
and machine states which make the “movements” in an automatic
formal system are equivalent to each other. These concepts are all
underlying the current technology of digital
computers, whose construction became
possible a decade after the publication of the
English mathematician. An automatic formal system is a
physical device that automatically handles the symbols of a
formal system by its rules. The theoretical Turing machine establishes
both an example of his theory of computation as evidence that certain types
of computing machines could be built. Actually a Universal Turing
Machine except for speed, which depends on the hardware, can
emulate any current computer, from supercomputers to personal computers,
with their complex structures, powerful computing capabilities,
since no matter the time spent. He proved that for any formal
system exists a Turing machine that can be
programmed to emulate it. Or in other words: for any well-defined
computational procedure, a Universal Turing Machine can simulate a mechanical
process to perform such procedures. From a theoretical point of
view, the importance of Turing machine is the fact that it is
a formal mathematical object. Through it the first
time, it gave a good definition of what it means
to compute something. And this raises the
question of what can be accurately computed with
such mathematical device, subject outside the
scope of this work and entering the field of
computational complexity. The ACE computer and
artificial intelligence Turing was Sent to America
to exchange information with the US intelligence and
know the projects related to computers, it took note
of the emerging electronic technologies and even
participate in another secret project, Delilah, a vocoder
(known in movie espionage as scramblers), entered into
contact with von Neumann (who wanted to bring him to
join them in their projects) and the engineers of Bell
(including Claude Shannon). Back to England, he joined
the National Physical Laboratory, where he
worked on the development of the Automatic Computing
Engine (ACE), one of the first attempts to
build a digital computer. At the end of the war, already held the
knowledge of new electronic technologies that could be used to increase the speed
of the then existing logic circuits. The real possibility of constructing
models of Universal Turing machines caused the British government
to invest in the construction of this new device, but the Americans
were more aggressive in their investments and ended up winning
the race to build computers. Turing, a victim of political intrigue, was
out of the center and control of new jobs. Its technical reports on hardware
designs and software ACE were ambitious, and the machine
originally imagined by him had been built immediately, the British
would not have embittered the delay about their colleagues on
the other side of the Atlantic. It was also during the season of
ACE Turing began to explore the relationship between the computer and
the mental processes by publishing an article Computing Machinery and
Intelligence (1950), about the possibility of building machines that
imitate the human brain function. Can a machine think, he wondered
in his article, and in addition to focusing on the subject machine
intelligence, Turing gained particular notoriety by trying to introduce,
through this article, a test to decide if you really can or not a
machine think imitating the man. In November 1991, the Boston Computer
Museum held a competition among eight programs to simulate the Turing Test, won
by a program called PC Therapist III. The problem of Turing test is behaviorist
nature, that is, only observes the outward behavior, which gives you
a character somewhat reductionist. Serious disputes have
occurred and still occur on this subject, which is beyond
the scope of this book. Computer programming Turing was also interested in
the planning of operations of a computer – which then began to
be called coding – regarding mathematical operations involved
there and began to write programming languages, then advanced
to the hardware of the time. Turing was convinced that calculation
operations were only one type of formal systems that
could be imitated by computers. In particular, he noticed how the
tables of his theoretical machine could become elements of an excellent grammar
that would use machines to modify their Turing operations innovated to start
drafting instructions tables, which automatically would convert decimal
notation we are used to in binary digits. These could be read by machines that began
to be built based on Boolean algebra. Turing foresaw so in the
future, and programmers could work with the languages
now known as high-level. He said: “The instruction tables
should be made by mathematicians with expertise in computers and some ability
to solve difficult problem solving. There will be enough work to be done
such, that all the known processes have to be converted in the form of
instructions tables at any given time. This task will continue in parallel
with the construction of the machine, to avoid delays at the end of this
and the production of results. Delays may occur due to
virtual unknown obstacles, to the point where it will be
better to let the obstacles there than spend time
designing something without problems (how many decades
will take these things?). This process of preparation of
instructions tables will be fascinating.” Turing’s work in Computing and
Mathematics was tragically ended by his suicide in June
1954 at the age of 42 years. Turing was gay and, after
the escape of two British spies the same trend for
the Soviet Union in the early 1950s, there was a
proper pressure on him to correct his condition through
the use of hormones. Turing, not bearing the heavy
pressure, took cyanide. Technological Prehistory As has been said, it was only
possible to reach the computers by theoretical discoveries of men who,
over the centuries, believed in the possibility of creating tools to
enhance human intellectual capacity, and devices to replace the most
mechanical aspects of thinking man so. And always this concern
manifested itself in building mechanisms to help both in
arithmetical calculation processes as in repetitive
or too simple tasks that could be replaced
by animals or machines. Physical devices that preceded
the computer primarily analog machines that fueled the final race
until the appearance of digital computers. Older devices The first devices that
have come to help the man to calculate have their
origin lost in time. It is the case, for example,
and abacus quadrant. The first, able to solve addition
problems, subtraction, multiplication and division up to 12 integers, and that probably
existed in Babylon around the year 3000 BC. It was widely used by Egyptian
civilizations, Greek, Chinese, and Roman, having been found
in Japan, at the end of world War II. The quadrant was an instrument for
astronomical calculation, have existed for hundreds of years before becoming
the subject of several improvements. The ancient Babylonians
and Greeks, for example, Ptolemy, used various
types of such devices to measure angles between
stars, mainly having been developed from the sixteenth
century in Europe. Another example is
the industry bar for trigonometric calculations
used to determine the height for positioning
the mouth of a cannon, which was developed from
the fifteenth century. The ancient Greeks came to
develop a kind of computer. In 1901, an old Greek boat was
discovered on the island of Antikythera. Inside there was a device
(now called Antikythera mechanism) constituted by
metal gears and pointers. As Derek J. de Solla Price, who
in 1955 rebuilt along with his colleagues this machine,
the Antikythera device is “like a large astronomical clock
without the part that regulates the movement, which uses mechanical devices
to avoid tedious calculations.” The discovery of this device,
dating from the first century BC, was a total
surprise, proving that some artisan Greek world western
Mediterranean was thinking regarding mechanization
and mathematization time. Logarithms and the first
mechanical computing devices John Napier, Baron of
Merchiston, is well known for the discovery of logarithms,
but also spent much of his life inventing tools
to help in arithmetic, especially for the use of
its first logarithm table. From Napier logarithms came another great
invention developed by the brilliant mathematician William Oughtred and
published in 1630: the slide rule. Won its current form by the year 1650
(a rule that moves between two other fixed block), having been forgotten
for two hundred years, to become the twentieth century the great
symbol of technological advance, with extremely widespread use until be
replaced by electronic calculators. With the development of
the first mechanical devices for automatic
calculation, effectively starts the technological
aspects that will lead to the construction of
the first computers. Preparing the way for the full
automation of the calculation process was performed by the
efforts of these early pioneers of Computing, who saw the possibility
of mechanization but did not have the tools and materials
suitable to realize their projects. Among these big names can not
fail to mention Wilhelm Schickard (1592-1635) and Pascal as
mentioned earlier and Leibniz. There are works on these inventions, and
only the primary element will be quoted the made up, as many of these ideas will be
present in some form in future computers. Almost all machines to perform
mechanical calculations of these three centuries from the XVI had six basic
elements in your configuration: • A mechanism by which a number
is entered into the machine. In the first project that was part of
another mechanism, called selector, making it something independent
in the most advanced machines; • A mechanism that selects and provides
the necessary movement to perform addition or subtraction of appropriate
amounts in the registration mechanisms; • A mechanism (typically some disks)
that can be positioned to indicate the value of a number stored in the
machine (also called register); • A mechanism to spread “goes one” for
all the digits of the register, if necessary, when one of the digits in a
result register advances from 9 to 0; • A mechanism to control
function to check the positioning of all wheels
after each addition cycle; • A ‘cleaning’ mechanism to prepare
the register to store the value zero. Architectures of computers
and operating systems The term computer architecture is the
ability to view a machine as a hierarchical set of levels that allows us to
understand how computers are organized. The first digital computers for
instance only had two levels. The first is called the level of the
digital logic, formed by valves at the beginning and then by
transistors, integrated circuits, etc. The second is called Level 1,
also called level microprogram, which is the level of
machine language, where all programming was done by zeros
and ones, and that would later be responsible for interpreting
the level 2 instructions. With Maurice Wilkes in 1951 came
another level, where the instructions were written in a more convenient
way for human understanding: the technique was to replace
each instruction of this new level of a set of instructions
from the previous level (machine level) or examine one
instruction at a time and perform the sequence of instructions
equivalent machine level. It simplifies the hardware
which now had only a minimal set of instructions, and thus
fewer circuits were needed. After that the evolution
of hardware advances with the new scientific
discoveries: almost the same time of appearance
of transistors, for example, the concept arose data bus, which
accelerated the speed of computers. At the same time appeared the
major operating systems (simply, an operating system is a set
of programs maintained on the computer all the time, freeing the
programmer related tasks directly with the operation of the machine),
such as DOS and OS, IBM. These evolved allowing new
concepts that improve the performance of
machines, such as the multiprogramming systems,
i.e., the ability to run multiple programs in parallel
on the same machine. If one of these programs
originates from a remote terminal, such a system
will be called timesharing. A significant milestone that
allowed these advances was the introduction of input and output
processors, also called channels. It motivated the
appearance of competition concepts, communication,
and synchronization: since two processors are operating
simultaneously, there is a need to provide mechanisms for synchronized
them and establish a communication
channel between them. It is the era of mainframe architectures: Support for computational
tasks and the development of applications are made in a central
area, called computer center. Terminals connected directly
to the machine are only used by people related to
the applications available. In the ’70s came the
supercomputers, machines that have innovated
in architecture. To date, the growth efficiency
of the computer was limited by technology, more specifically
for processing scalar requiring that the CPU of a
computer to finish a task to begin taking another, producing
the von Neumann bottleneck. A breakthrough came with the Cray-1
supercomputer, the Cray Research in 1971. It was the first pipeline machine,
which processor an instruction executed by dividing it into parts,
as in assembly line of a car. While the second part of the
statement was being processed, the first part of another
education began to be crafted. The subsequent evolution was called Vector
Machine or machine SIMD (Single Instruction Multiple Data) processors which work with
more than one dataset at the same time. A little later came the MIMD architecture
(multiple instructions multiple data) and appeared multiprocessor machines as the
Connection Machine, with 65,536 processors. This technology also
provided the advantage of working with existing
eight-bit expansion cards on the market and
relatively inexpensive eight-bit devices, such
as controller chips. In the search for software
IBM was the Digital Research doors to see the ability to
port your operating system a great success! CP/M for architecture 8086, but this rejected
the exclusive contract presented by IBM. So the IBM team headed
for Microsoft Office, who hoped to get a
version of BASIC and ended up signing a contract not only this
software but also on the operating system. Microsoft acquired and increased an
operating system 8086 from Seattle Computer Products – QDOS – licensing it to IBM,
which began to market it with PC-DOS name. The years of the 1980s could
be characterized by software improvement – both operating
systems and utilities: spreadsheets, text editors,
and others – to the DOS standard and the development
of a market clones of different types of
machines that would be able running programs
designed to the standard. Apple continued to be satisfied
with its Apple II family, although failing in the
introduction of the Apple III and formidable LISA, the first attempt
to popularize the combination of mouse, windows, icons and
graphical user interface. But the price of US $ 10,000.00
startled and amazed the market. The next step to be taken – not to mention the evolution
and improvement of hardware without which it
would not be possible – would be the gradual transition of
applications for DOS environment – real sea products – to a new environmental
standard, which was beginning to take shape definitive, and starred in the beginning of
a new age in the history of microcomputers: the Windows operating system, which has
become the dominant standard for PC applications, making Microsoft a leader
in defining multimedia specifications. It is important however to make justice: Windows pattern inspired by the standard
Macintosh, released by Apple in 1984: a computer that was able
to offer more than a DOS prompt and a
character-based interface; he could have multiple windows,
drop down menus and mouse. Unfortunately, the Macintosh
was not compatible with the programs and existing applications
and was not expandable. Computing as a Science Alongside this evolution of hardware
and software, Computer opened in range and new trends have emerged within it,
incorporating these two entities. Artificial Intelligence,
Theory of Computational Complexity and Database Theory
opened new fields of study. In the 1960s computer science
has become a true discipline. The first person to receive a title of Ph.
D. from a computer science department was Richard Wexelblat at the
University of Pennsylvania in 1965. They have consolidated the studies
on the Theory of Automata and Languages Theory Formal mainly with
Noam Chomsky and Michael Rabin. The birth of the branch of
formal specifications, which introduced a new paradigm in the
development of computer systems, came in this decade, with the
beginning of the search for the correctness of programs through
the use of formal methods. W R. Floyd, in 1967, proposed that the
semantics of programming languages were defined independently of the specific
processors intended that language. The definition can be given,
according to Floyd, in terms of the method for test programs
expressed in language. His work introduced what
became known as the method of notes (assertive) Inductive
for verification (test) program and one involving
technical “sets with sorting well founded to prove
the end of a program.” An extension of Floyd’s ideas was
proposed by C. A. Hoare in 1969. Hoare made an axiomatic
theory of programs that allows the application of
the method of invariants Floyd programs texts
expressed in programming languages whose semantics
is precisely formulated. This work has become even
one of the foundations of what was later called
“structured programming”. Dijkstra developed the
idea that the definition (in the style proposed
by Hoare) can be used for the derivation (synthesis) of
a program and not just for your check. From these studies emerged
Software Engineering, which aims to ensure the correctness
in building systems. The development of computer systems so
far was done in a way almost handmade. There was some criteria
guidance during the process. This turned out to be fatal,
as revealed certain studies, developed in the 1970s on
the development of systems: lack of correctness and consistency,
low quality, extremely costly maintenance because of problems not
detected by the absence of a validation stricter requirements do not reuse code,
implementation of missed deadlines as a result of errors detected over
this same implementation phase, etc. Obeying a greater degree of formalization,
they appeared as a first reaction to this informal approach models and
system development methods called structured, which actually are sets of
rules and regulations that guide the various stages of system development
and the transitions between them. It is the systematic approach. Yet here is not a formalism
defined with precise rules. Prototyping and object
orientation are approaches that can be
considered systematic. The rigorous approach already has a
formal linguistic system to document the development stages and strict rules for
the transition from one stage to another. There is no requirement
that the correctness of statements of
changes be made. The spread of computer literacy When history look back and study
the twentieth century, among other things, you realize that, from a
scientific point of view, they are characterized as times in
which it produced a technological acceleration and a breakthrough
in unprecedented communications. Not easy to find similar historical
situations to technological expansion witnessed in these
last fifty years of the century. After the iron revolution, electricity,
petroleum, chemical, came the revolution supported in electronics
and development of computers. From the seventies
began the large-scale integration of television,
telecommunications and information technology,
in a process that tends to set up integrated
information networks, with a communication
matrix based on digital information, with great
ability to serve data, photos, graphics, words,
sounds, images, broadcast on various printed and
audiovisual media. One can even say that, in a
sense, the media are being suppressed because everything
is becoming electronic. The integration of the media also
generates a progressive fusion of the intellectual and industrial activities
in the field of information. Journalists from newsrooms of major
newspapers and news agencies, artists, student community, researchers
are working on a computer screen. In some societies, such as the
North American for example, almost 50% (1955 data) of the economically
active population is dedicated to industrial, commercial,
cultural, social and informational related to collection, processing
and dissemination of information. There is an increased
informational efficiency every day, and cheapen increasingly
technological costs. Not forgetting that the
computer, unlike other machines (handling, processing or
transporting matter and energy) manipulates, transforms and
carries a much cleaner element and less consumer of
energy and raw materials. It opens thus the door to a growth
of almost unlimited information. Since you are dealing mainly
about the evolution of ideas and concepts that led to the
emergence and development of computer science, we
can now speak of a larger supra-concept, a result that
Computer helped catalyze: the emergence of the Company Information. Without wishing to enter the
theme, worthy of a unique work and historical,
anthropological, sociological and even psychological
implications that are beyond the present scope, two
considerations will be made: the problem of excess
information and the danger of impoverishment that can be caused
by using improper computer.

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