If there is a possibility of several things going wrong, the one that will cause the most damage will be the one to go wrong.
Murphy’s fifth law:
If anything just cannot go wrong, it will anyway.
Murphy’s sixth law:
Left to themselves, things tend to go from bad to worse.
Murphy’s seventh law:
If everything seems to go well, you have obviously overlooked something.
Some useful advice:
Do not believe in miracles – rely on them.
When working toward the solution of a problem, it always helps if you know the answer.
If your idea works – something has gone wrong.
Never underestimate the power of human stupidity.
Smile! Things can only get worse.
U
NIT
3
Information for study
Brief history of computer technology
To err is human, but to really foul
things up requires a computer.
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The evolution of digital computing is often divided into generations. Each generation is characterized by dramatic improvements over the previous generation in the technology used to build computers, the international organization of computer systems, and programming languages.
The mechanical era (1623–1945)
The idea of using machines to solve mathematical problems can be traced at least as far as the early 17th century, when mathematicians designed and implemented calculators that were capable of addition, subtraction, multiplication, and division.
The first multi-purpose, i.e. programmable, computing device was begun in 1823 but never completed. A more ambitious machine was the Analytical Engine. It was designed in 1842, but unfortunately it also was only partially completed, but nevertheless it was the first one to be used in computational science. By 1853 engineers had constructed a machine that won a gold medal at the Exhibition in Paris, and later it was used to calculate the orbit of Mars.
First generation electronic computers (1937–1953)
Three machines have been promoted at various times as the first electronic computers. These machines used electronic switches, in the form of vacuum tubes, instead of electromechanical relays. In principal the electronic switches would be more reliable, since they would have no moving parts, that would wear out, but the technology was still new at that time and the tubes were comparable to relays in reliability. Electronic components had one major benefit, however: they could «open» and «close» about 1000 time faster than mechanical switches.
The earliest attempt to build an electronic computer was realized in 1937, when a machine was created that could solve systems of partial differential equations. Later, by 1941, the scientists succeeded in building a machine that could solve 29 simultaneous equations with 29 unknowns. However, the machine was not programmable, and was more of an electronic calculator.
A second early electronic machine was Colossus, designed for the British military in 1943. This machine played an important role in breaking codes used by the German army in World War II.
Turing’s main contribution to the field of computer science was the idea of the Turing machine, a mathematical formalism widely used in the study of computable functions.
The first general purpose programmable electronic computer was the Electronic Numerical Integrator and Computer (ENIAC) built at the University of Pennsylvania. Work began in 1943, founded by the Army Ordnance Department, which needed a way to compute ballistics during World War II.
The machine wasn’t completed until 1945, but then it was used extensively for calcu-
lations during the design of the hydrogen bomb. By the time it was decommissioned in 1955 and used for solving different civil tasks including weather prediction a group of scientists began work on a new machine. The main contribution of their new project, was the notion of stored program. There is some controversy over who deserves the credit for this idea, but none over how important the idea was to the future of general purpose computers. Through the use of a memory that was large enough to hold both instructions and data, and using the program stored in memory to control the order of arithmetic operations, this machine was able to run orders of magnitude faster than it was done before. By storing instructions in the same medium as data, designers could concentrate on improving the internal structure of the computer without worrying about matching it to the speed of an external control.
By recognizing that functions, in the form of a sequence of instructions for a computer, can be encoded as numbers, the scientists realized the instructions could be stored in the computer’s memory along with numerical data.
Software technology during this period was very primitive. The first programs were written out in the machine code, i.e. programmers directly wrote down the numbers that corresponded to the instructions they wanted to store in memory. By the 1950s programmers were using a symbolic notation, known as assembly language, than hand-translating the symbolic notation into machine code. Later programs known as assemblers performed the translation task.
As primitive as they were, these first electronic machines were quite useful in applied science and engineering. One of the scientists estimated that it would take eight hours to solve a set of equations with eight unknowns using a previous calculator, and 381 hours to solve 29 equations for 29 unknowns. The up to time computer was able to complete the task in under an hour. The first problem run on it, a numerical simulation used in the design of the hydrogen bomb, required 20 seconds, as opposed to forty hours using mechanical calculators. Later the first commercially successful computer was developed. In 1952, 45 minutes after the polls closed and with 7% of the vote counted, it predicted Eisenhower would defeat Stevenson with 438 electoral votes (he ended up with 442).
Second generation (1954-1962)
The second generation saw several important developments at all levels of computer system design, from the technology used to build the basic circuits to the programming languages used to write scientific applications.
Electronic switches in this era were based on discrete diode and transistor technology with a switching time of approximately 0.3 microseconds. The first machines were built with this technology at Bell- and Lincoln Laboratories. Memory technology was based on magnetic cores which could be accessed in random order as opposed to the previous devices.
During this second generation many high level programming languages were introduced, including FORTRAN (1956), ALGOL (1958), and COBOL (1959). Important commercial machines of this era include the IBM 704 and its successors, the 709 and 70094.
The second generation also saw the first supercomputers designed specifically for numeric processing in scientific application. The term «supercomputer» is generally reserved for a machine that is an order of magnitude more powerful than other machines of this era.
Third generation (1963-1972)
The third generation brought huge gains in computational power. Innovations in this era include the use of integrated circuits, or ICs (semiconductor devices with several transistors built into one physical component), semiconductor memories starting to be used instead of magnetic cores, microprogramming as a technique for efficiently designing complex processors, the coming age of parallel processing, and the introduction of operating system.
The first ICs were based on small-scale integration (SSI) circuits, which had around 10 devices per circuit (or «chip»), and evolved to the use of circuits, which had up to 100 devices per chip. Multilayered printed circuits were developed and core memory was replaced by faster, solid state memory. Computer designers began to take advantage of parallelism by using multiple function units. In 1964, Seymour Cray developed the CDC 6600, which was able to attain a computation rate of 1 million floating point operations per second (1 Mflops). Five years later the CDC 7600 was capable of executing at 10 Mflops. At the same time IBM and other companies released computers of about the same rate of operations.
During this period Cambridge and the University of London cooperated in the development of CPL (Combined Programming Language, 1963). CPL was an attempt to simplify the complicated and sophisticated ALGOL, but this program was still hard to learn; therefore it was followed by BCPL (Basic Computer Programming Language, 1967). Later (1970) in Bell Labs another simplification of CPL was developed and called «B».
The incredibly fast progress in hardware, software and its technologies has begun.
Computer speech
Think twice before you speak to a friend in need.
Bierce
Compression It is often possible to remove redundant information or to process it in lesser amount of storage space. Usually when a file has been compressed, it cannot be used until it is uncompressed.
Embedded An embedded system is a computer that is inside another device and acts as a component of that device. E.g. cars have an embedded computer that helps regulate their day to day operations.
Extension Filename extensions allow a rough grouping of different file types by putting a tag at the end of the name.
Partition Sometimes due to hardware limitations, discs have to be divided into smaller pieces. These pieces are called partitions.
Protocol is a means of communication used between computers. If both computers recognize the same protocol, they can communicate over the same network or even via a simple direct modem connection regardless whether or not they are themselves of the same type.
UPS Abbreviation for an uninterrupted power supply. It includes heavy duty batteries to help smooth out its input power source.
2. Exercises