DIGITAL COMPUTERS — McCORMICK 283 



would fail faster than they could be replaced. Nevertheless, this and 

 many other problems were solved, and many thousands of computers 

 have been built since tlien. It was 1950 before the first digital com- 

 puter was built with all the characteristics now considered to be 

 essential. 



Interestingly, many of the devices adapted for use in computers 

 have been available for some time. The basic bistable electronic cir- 

 cuit (the fiip-flop) was invented in 1919. The equipment for mput 

 to and output from digital computers is adapted from communication 

 and business-accounting devices. Punched paper tape was used by 

 Samuel F. B. Morse, inventor of the telegraph. The familiar punched 

 card was used by Jacquard in 1801 and is still in use to control weav- 

 ing looms for making designs in cloth. (Babbage had intended to 

 use punched cards in his analytical engme.) Hollerith adapted 

 punched cards for the 1890 census, and many other uses have been 

 made of them since then. And, finally, the mathematics needed for 

 the logical design of digital computers was developed by another Eng- 

 lish mathematician of the last century, George Boole, 1815-64. 



COMPUTERS VERSUS CALCULATORS 



The solving of mathematical problems and processing of business 

 data have been accomplished for some time by the use of manual cal- 

 culators. How are computers different from calculators, which also 

 do arithmetic operations ? To answer this we must realize that doing 

 the arithmetic operations is only part of the process of solving a prob- 

 lem when using a calculator. Deciding what numbers to put into the 

 calculator, putting them into it, and after performing the arithmetic, 

 deciding what to do with the numbers resulting from it and then doing 

 it all involve more time than the aritlmietic itself. 



Computers differ from calculators in that computers do the complete 

 job of solving a problem. They contain within themselves all the data 

 pertinent to a problem and all the instructions for solving it, includ- 

 ing alternate sets of instructions to be followed on the basis of deci- 

 sions which the machine itself can make. Thus a digital computer is 

 capable of completely solving a problem at electronic speeds without 

 human intervention during the solution. However, the setting up of 

 a computer to do this is frequently time consuming and expensive. 



But what has a computer really gained over a calculator and its 

 operator except speed ? First, we must realize that for many purposes 

 this speed advantage itself is sufficient gain. Being able to do hun- 

 dreds of thousands or even millions of operations in the time formerly 

 required for one is a tremendous advantage in solving a problem. 



Ways for solving problems involving a very large number of opera- 

 tions have been known for many years, but the time and labor required 



