IT HARDWARE MAINTENANCE COMPANIES
IT Hardware Maintenance Companies Additional related topics of current interest may also be found on the book’s website. The website also contains numerous links to reference materials, both general to computing as well as specific to individual topics discussed within the book.
IT Hardware Maintenance Companies Although a study of the history of computing is generally outside the scope of this book, a brief introduction is useful in showing the wide-ranging and quirky path by which IT has arrived to its present position. It is of particular interest to note that nearly all of the revolutionary concepts that define computer systems today were developed between thirty and sixty years ago; today’s advances are more evolutionary and incremental in nature. This suggests that an understanding of the basic concepts that we are presenting in this IT Hardware Maintenance Companies book should serve you, the reader, well in your ability to understand the importance and significance of future developments as they occur.
IT Hardware Maintenance Companies It is not possible, nor particularly useful, to identify the date of the ‘‘invention’’ of the computer. Indeed it has always been the aspiration of humankind to create devices that would simplify people’s work. Thus, it is not surprising that people were envisioning mechanical devices to simplify the jobs of routine data processing and calculation even in ancient times. In fact, there is recent evidence of the existence of an ancient computing device used for astronomical calculations. Instead, this discussion covers just a few of the major developments related to computer architecture
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IT Hardware Maintenance Companies Charles Babbage, an English mathematician who lived in the early 1800s, spent much of his own personal fortune attempting to build a mechanical calculating machine that he called an ‘‘analytical engine.’’ The analytical engine resembles the modern computer in many conceptual ways. A photo of an early version of the analytical engine is shown in Figure 1.12. Babbage’s machine envisioned the use of Jacquard’s punched cards for input data and for the program, provided memory for internal storage, performed calculations as specified by the program using a central processing unit known as a ‘‘mill,’’ and printed output. Augusta Ada Byron, Countess of Lovelace and the daughter of the poet Lord Byron, worked closely with Babbage and developed many of the fundamental ideas of programming and program design, including the concepts of branches and loops
IT Hardware Maintenance Companies In this context, one could consider the abacus, already in use as early as 500 BC by the ancient Greeks and Romans, to be an early predecessor of the computer. Certainly, the abacus was capable of performing calculations and storing data. Actually, if one were to build a binary numbered abacus, its calculations would very closely resemble those of the computer
IT Hardware Maintenance Companies The abacus remained in common use until the 1500s and, in fact, is still considered an effective calculating tool in some cultures today. In the late 1500s, though, European inventors again began to put their minds to the problem of automatic calculation. Blaise Pascal, a noted French mathematician of the 1600s, invented a calculating machine in 1642 at the age of nineteen, although he was never able to construct the machine. In 1801, Joseph Marie Jacquard invented a loom that used punched cards to control the patterns woven into cloth. The program provided by the punched cards controlled rods that raised and lowered different threads in the correct sequence to print a particular pattern. This is the first documented application of the use of some form of storage to hold a program for the use of a semiautomated, programmable machine
IT Hardware Maintenance Companies A block diagram of the Babbage analytical engine is shown in Figure 1.13. The mill was capable of selecting one of four arithmetic operations, and of testing the sign of a number with a different program branch specified for each result. The sequence of operation was specified by instructions on the operation cards. The operation cards could be advanced or reversed as a means of implementing a sort of ‘‘goto’’ instruction. The second set of cards, known as variable cards, were to be used to specify particular memory locations for the data involved in the calculations
IT Hardware Maintenance Companies Babbage envisioned a memory of one thousand 50-digit decimal numbers. Each digit was to be stored using a ten-toothed gear known as a counter wheel. Although the analytical engine was never completed, it should be apparent to you that it contains all the essential elements of today’s computers. At approximately the same time, another English mathematician, George Boole, developed the binary theory of logic that bears his name, Boolean logic. He also recognized the relationship between binary arithmetic and Boolean logic that makes possible the circuitry that implements the modern electronic computer. IT Hardware Maintenance Companies
IT Hardware Maintenance Companies The first totally electronic digital computer was apparently devised by John V. Atanasoff, a physicist at Iowa State College, in 1937. The machine was built in 1939 by Atanasoff and a graduate student, Clifford Berry, using electronic vacuum tubes as the switching components. The machine was known as ABC, for Atanasoff-Berry Computer. It is claimed that Atanasoff worked out the original details as he drove restlessly late one winter night from his house in Iowa to a bar in neighboring Illinois. The machine was not intended as a general-purpose computer, but was built to solve physics equations that Atanasoff was working on at the time. There is some doubt as to whether the machine ever worked completely IT Hardware Maintenance Companies