Citation de lanard
In the eighteenth century (and indeed up to the 1940s), a computer was a person who calculated numbers for hire. Tables of logarithms were always needed, and trigonometric tables were essential for nautical navigation using the stars and planets. If you wanted to publish a new set of tables, you would hire a bunch of computers, set them to work, and then assemble all the results. Errors could creep in at any stage of this process, of course, from the initial calculation to setting up the type to print the final pages.
The desire to eliminate errors from mathematical tables motivated the work of Charles Babbage (1791-1871), a British mathematician and economist who was almost an exact contemporaty of Samuel Morse.
At the time, mathematical tables (of logarithms, for example) were not created by calculating an actual logarithm for each and every entry in the table. This would have taken far too long. Instead, the logarithms were calculated for select numbers, and then numbers in between were calculated by interpolation, using what are called differences in relatively simple calculations.
Beginning about 1820, Babbage believed that he could design and build a machine that would automate the process of contructing a table, even to the point of setting up type for pinting. This would eliminate errors. He conceived the Difference Engine, and basically it was a big mechanical adding machine. Multidigit decimal numbers were represented by geared wheels that could be in any of 10 positions. Negatives were handled using the ten's complement. Despite some early models that showed Babbage's design to be sound and some grants from the British government (never enough, of course), the Difference Engine was never completed. Babbage abandoned work on it in 1833.
By that time, however, Babbage had an even better idea. If was called the Analytical Engine, and through repeated design and redesign (with a few small models and parts of it actually built) it consumed Babbage off and on until his death. The Analytical Eginge is the closest thing to a computer the nineteenth century has to offer. In Babbage's design, it had a store (comparable to our concept of memory) and a mill (the arithmetic unit). Multiplication could be handled by repeated addition, and division by repeated substraction.
What's most intriguing about the Analytical Engine is that it could be programmed using cards that were adapted from the crds used in the Jacquard pattern-weaving loom. As Augusta Ada Byron, Countess of Lovelac (1815-1852), put it (in notes to her translation of an article written by an Italian mathematician about Babbage's Analytical Engine), "We may say that the Analytical Engine weaves algebrical patterns just as the Jacquard-loom weaves flowers and leaves."
Babbage seems to be the first person to understand the importance of a conditionnal jump in computers. here's Ada Byron again : "A cycle of operations, then, must be understood to signify any set fo operations which is repeated more than once. It is equally a cycle, whether it be repeated twice only, or an indefinite number of times ; for it is the fact of a repetition occuring at all that constitutes it such. In many cases of analysis there is a recurring group of one or more cycles ; that is, a cycle of cycle, or a cycle of cycles."
The desire to eliminate errors from mathematical tables motivated the work of Charles Babbage (1791-1871), a British mathematician and economist who was almost an exact contemporaty of Samuel Morse.
At the time, mathematical tables (of logarithms, for example) were not created by calculating an actual logarithm for each and every entry in the table. This would have taken far too long. Instead, the logarithms were calculated for select numbers, and then numbers in between were calculated by interpolation, using what are called differences in relatively simple calculations.
Beginning about 1820, Babbage believed that he could design and build a machine that would automate the process of contructing a table, even to the point of setting up type for pinting. This would eliminate errors. He conceived the Difference Engine, and basically it was a big mechanical adding machine. Multidigit decimal numbers were represented by geared wheels that could be in any of 10 positions. Negatives were handled using the ten's complement. Despite some early models that showed Babbage's design to be sound and some grants from the British government (never enough, of course), the Difference Engine was never completed. Babbage abandoned work on it in 1833.
By that time, however, Babbage had an even better idea. If was called the Analytical Engine, and through repeated design and redesign (with a few small models and parts of it actually built) it consumed Babbage off and on until his death. The Analytical Eginge is the closest thing to a computer the nineteenth century has to offer. In Babbage's design, it had a store (comparable to our concept of memory) and a mill (the arithmetic unit). Multiplication could be handled by repeated addition, and division by repeated substraction.
What's most intriguing about the Analytical Engine is that it could be programmed using cards that were adapted from the crds used in the Jacquard pattern-weaving loom. As Augusta Ada Byron, Countess of Lovelac (1815-1852), put it (in notes to her translation of an article written by an Italian mathematician about Babbage's Analytical Engine), "We may say that the Analytical Engine weaves algebrical patterns just as the Jacquard-loom weaves flowers and leaves."
Babbage seems to be the first person to understand the importance of a conditionnal jump in computers. here's Ada Byron again : "A cycle of operations, then, must be understood to signify any set fo operations which is repeated more than once. It is equally a cycle, whether it be repeated twice only, or an indefinite number of times ; for it is the fact of a repetition occuring at all that constitutes it such. In many cases of analysis there is a recurring group of one or more cycles ; that is, a cycle of cycle, or a cycle of cycles."