The history of personal computing

One of the most important developments leading to the personal computer revolution was the invention of the semiconductor, or transistor, in 1948. This feat was accomplished by John Bardeen, Walter Brattain, and William Shockley, who were engineers working at Belt Telephone Laboratories. The transistor, nothing more than a solid-stale electronic switch, replaced the much larger vacuum tube and consumed significantly less power in tube's job. Thus, a computer system built with transistors was much smaller and more efficient.

The tube also could act as a switch but was inefficient in this role. A tube consumed a great deal of electrical power and gave off enormous heat.

The switch to transistors began the trend toward miniaturization that has enabled today's small laptop PC systems, which run on batteries, to have more computing power than many earlier systems that filled rooms and consumed huge amounts of electrical power.

In 1959, engineers at Texas instruments figured out how to put more than one transistor on the same base material and connect the transistors without wires. Thus, the integrated circuit, or 1C, was born. The first 1C contained only six transistors, but the Intel 80386 in many of today's systems has 280,000. Today, 1C can be built with millions of transistors on-board.

In 1969, a company called Intel made waves in the industry by introducing a 1 К ‑ bit memory chip, which was much larger than anything else available at the time. Because of Intel's success in chip manufacturing, the company Japanese-calculator manufacturer called Busicomp and was asked to produce 12 chips for creation of Busicomp's calculator scientific designs. Engineers at Intel took the 12-chtp design and incorporated all the desired functions and capabilities into a single" generic" multipurpose chip. This chip was different from previous designs. The new chip read a variable set of instructions from memory, which Intel already had been producing. The concept was to design what was almost an entire computing device on a single chip. This first microprocessor was the Intel 4004, a 4-bit microprocessor, introduced in 1971. The successor to the 4004 was the 8008 5-bit microprocessor in 1972.

In 1973, some of the first microcomputer kits based on the 8008 chip were developed. In late 1973, Intel introduced the 8080 microprocessor, which was 10 time faster than the earlier 8008 chip and also could have 64 К of memory.

With a cover story In the January 1975 issue of Popular Electronics magazine, a company called MITS introduced the Altair kit, which is generally considered to be the first personal computer- This kit included an 8080 processor, a power supply, a front panel with a great deal of lights, and an enormous 256 bytes (not kilobytes) of memory. The kit sold for 5395 and had to be assembled. The new processor-inspired other companies to write programs, including the CP/M (Control Program for Microprocessors) operating system and first version of Microsoft BASIC-NOW things really started moving. IBM introduced its first "personal computer" in 1975. The Model 5100 had 16K of memory, a built-in BASIC language Interpreter, and a built-in cartridge tape drive for storage. The Mode! 5100 was succeeded by the 5110 and 5120 before IBM introduced the IBM Personal Computer (which was called the Model 5150).

In 1976, a new company called Apple Computer introduced the Apple I. This system consisted of a main circuit board screwed onto a piece of plywood. A case and power supply were not included; the buyer had to supply them. The Apple I was followed in 1977 by the Apple II. The Apple II, because of its enormous success, helped to set the standards for nearly all the microcomputers, including the IBM PC.

In 1980, the microcomputer world was dominated by two main factions of computers. One faction was the Apple II, which claimed of loyal users and a gigantic software base that was grow at a fantastic rate. Also available were ail the systems that had evolved from the original MITS Altair. These system were compatible with each other and were distinguished by their use of the CP/M operating system and expansion slots that followed the S-100 (for slot with 100 pins) standard. Although built by a variety of companies and selling under various names, these systems all were able (for the most part) to use the same software and plug-in hardware

ACCURATE TIME

All the world lives by the “Dearth time" or the "star time" as the astronomers call it. It means that our clocks are timed according to the earth's rotation, for the turning earth is the master clock by which all other clocks are set¹.

This nightly task of timing the earth's rotation is carried out at the observatories of various countries. What an astronomer does is to determine how the star time compares with the average time of the observatory's master clocks.

To keep them as exact as possible, the clocks are protected from all outside influence. The pendulum clocks are kept underground, away from vibrations and changing temperatures Each pendulum swings in a vacuum (that is, in a case from which the air has been pumped out), for air resistance would gradually slow down their time of swing. Each pendulum swings in a different direction, too, so that the vibration of one will not affect another.

The observatories' time signals are based on crystal clocks since they are the most accurate. Vibrating crystals by means' of which these clocks are run, are sealed inside vacuum tubes and kept vibrating by electric current.

To provide the accurate telling of time an exact measure of time is required. Such a measure is the "standard second," that is made available just as the "standard metre" and other units of measurement.

In today's world not only the second but even a fraction of a second plays an important part.

Our electric clocks are run by current that vibrates-60 times a second. If they vary from that, they are wrong.

X-ray pictures taken in one millionth of a second are now possible, to reveal what is happening inside machines operating at a very high speed.

But we are chiefly interested in the time we live by, standard time, divided into hours and minutes. An hour is a man-made thing, just one-twenty-fourth part of the time it takes for the earth to make one complete turn.

To-day the world runs on standard time, but not so long ago most localities used their own local time. In 1884 an International Meridian Conference extended standard time to the entire world which was divided into 24 time zones. Standard time in each zone varied by one hour from the next, the time at Greenwich being taken as the zero point.

In future we may use atoms to measure time, because they have within them very precise frequencies of oscillation that will prevent the clock from gaining or losing. A crystal could be adjusted to vibrate at the same rate as the atoms of some pure element.

The crystal's vibrations could be used to run a clock. Such an atom-controlled clock would keep more accurate time than the turning earth itself.

Note

1. to set a clock ‑ поставить часы по точному времени

Date: 2016-07-18; view: 345; Нарушение авторских прав