The development of computers
The first computers used thousands of separate electrical components connected together with wires. In the late 1940s, computers were made using vacuum tubes, resistors, and diodes. These computers were called first generation computers.
In 1956, transistors were invented. Transistors are made from materials called semiconductors. Computers using transistors were called second generation computers. Second generation computers were smaller than first generation computers. Second generation computers also used less electrical power. Both first and second generation computers were very expensive.
Integrated circuits
Computer components (such as transistors, diodes, resistors) can now be made from semiconductor materials of different shapes. Nowadays, complete circuits can be made from a single piece of semiconductor, called a chip. Such circuits are called integrated circuits (IC's). Computers using integrated circuits were first produced in the 1960s. They were known as third generation computers. Their integrated circuits had about 200 components on a single chip. Today, we can produce millions components on a single chip.
With the invention of chips, computer manufacture has become much simpler. The manufacturer does not have to connect thousands of components together. Most of the connections are made inside the chip. It is even possible to build a complete processor on a single chip. A processor on a single chip is called a microprocessor.
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The year 1958 was exactly a banner year in the course of human events, but it did usher (возвещать) in a computing classic when Sperry Rand first presented the Universal Automatic Computer Model II (Univac II) to the world.
Univac II was able to support the accounting needs of an extraordinary number of Computer Data customers, more than 1,000, who probably didn't realize or care that their work was being done on the clanking antique.
When Sperry Rand first built the Univac II, it was hailed as an impressive achievement in the emerging science of automated data processing. And, indeed, it was, even though only about 32 were ever built.
The Univac II had much greater speed (160 msec add time versus 525) and memory (10,000 12-bit words of core versus 1,000 words of mercury delay line) (ртутная линия задержки) than its predecessor, the Univac I, which is often acknowledged as the first commercial computer.
Characterized by tube technology, the II boasted more than 5,000 vacuum tubes, or "valves", uncounted miles of wiring, an immense water cooling system, an enormous, tricky console, and a central processor that was 9 feet high, 10 feet wide, and 14 feet long.
A walk-in CPU
In fact, the CPU was so large that it had a door on it and interior space enough for a person to stand up and move around in it. The computer and its peripherals, which together weighed more than 8 Ions, required a room with about 2,000 square feet of floor space. Its water cooling equipment was nearly as big. Input was in the form of I/2-inch magnetic metallic foil (фольга) tape reels (бобина) that weighed about 2 1/2 pounds – each and were, as one might expect, very durable (прочный). The foil tape is no longer made, but the original tapes worked fine right up until the end. When a bad spot appeared on the tape, it was possible to simply punch a hole in it at that point and continue to use it; the tape drives (дисководы) would skip over the hole.
The II was not basically a punched card machine, as were most of its brethren (семейство). That magnetic foil tape was the input medium, too. Data entry was done, as it had been on the Univac I, using key-to-tape devices – long before the Mohawk Data Sciences engineers and others put their minds to the matter.
Unlike newer machines, Univac II had a radio speaker that was used to "listen" to its operations when troubleshooting (поиск неисправности) the system. Any deviation (отклонение) in the sound of the noizy computer, and the bug (техн. дефект) usually was spotted. Inventive programmers took advantage of this feature, in dull (скучный) moments, and wrote routines to make it play music.
According to various users of the old machines, it was the most complicated and overdesigned piece of equipment ever built – and one of the most dependable.
The "high speed" printer that worked with the computer was actually a Univac I device that was five years older than the Univac II. It was capable of a then incredible 600 lines per minute on alphanumerics and was good for 800 lpm when push a little (ускорять).
The programming language used with the computer was, appropriately enough, machine language. But the third generation software developed by Computer Data over the years enabled Univac II to perform accounting applications that included payroll (оплата) accounts payable and receivable (прием и оплата счетов), invoicing (выписка накладных), and inventory (опись) control in a kind of "pipelined" batch mode.
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The purpose of the Univac II.
The basic parts.
The characteristic features of the Univac II.
The input media.
The output media.
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Within a computer system, data is represented by electrical signals. When a user enters data through the keyboard, the data is sent to the CPU as a pattern of electrical pulses.
At any given point in the pattern, there is either a pulse or no pulse. Each point in the pattern (pulse or no pulse) is called a bit. A bit is the smallest unit of data.
Computers are not designed to process single bits. Usually they process 8-bit units. A collection of 8 bits is called a byte. Some larger computers can also process 16 bits (i.e. 2 bytes) or 32 bits (i.e. 4 bytes) with one instruction.
Character codes
All data inside the computer is represented by combinations of bits. A letter or number can be represented by a pattern of pulses. For example, the letter 'A' can be sent as it is shown in the Fig. 1.
Fig. 1. Representation of letter 'A'.
Fig. 2. Representation of Dumber '3'.
The number '3' can be sent as it is shown in the Fig. 2.
Patterns of this kind are examples of a code. The code represents each character as a certain pattern of bits. In the code, a pulse is represented by '1'. No pulse is represented by '0'. Thus the letter 'A' can be written as '1000001'. The number '3' can be written as '0110011'.
The above examples are part of a very common code called the American Standard Code for Information Interchange (ASCII). ASCII is pronounced as "as key". Here each character is represented by 7 bits. The ASCII code is therefore called a 7-bit code. Another character code, called EBCDIC, is an 8-bit code. In EBCDIC (extended binary-coded decimal interchange code расширенный двоично-десятичный код для обмена информацией), the letter 'A' is represented by '11000001' and '3' is represented by '11110011'. Each computer is designed to use a single code, e.g. ASCII or EBCDIC. However, the computer can be programmed to convert signals from one code to another.
Binary codes
Numbers can be represented by the ASCII or EBCDIC code. There is another representation for numbers called binary representation. This is
useful if numbers have to be processed mathematically.
The numbers in everyday use are decimal numbers. Decimal numbers use ten symbols (0, 1, 2, 3, 4, 5, 6, 7, 8, 9). Binary numbers do not use the symbols 2, 3, 4, 5, 6, 7, 8, or 9. They use only two symbols 0 and 1. In Figure the decimal number on the left represents the same number as the binary code on the right.
DECIMAL |
BINARY |
0 |
0000 |
1 |
0001 |
2 |
0010 |
3 |
0011 |
4 |
0100 |
5 |
0101 |
6 |
0110 |
7 |
0111 |
8 |
1000 |
Numbers represented by the binary code and by the ASCII code both use the symbols 0 and 1. However, binary numbers require less storage space. Binary numbers are also simple for the computer to process.