Text 14. Digital Computers

The desk calculator is an example of a class of devices operating as digital computers, where the input and output are numerical digits in contrast to the analog computer, in which the input and output are physical quantities. The desk calculator performs various arithme­tical operations largely through an ability to add or subtract, the human operator directing, or programming the machine in such a way that through a sequence of additions or subtractions many more complex arithmetical operations are performed.

Assuming proper machine operation, the accuracy of a digital com­puter is dependent only on the number of significant digits carried through the computation, this number being largely fixed by ques­tions of allowable complexity and cost of the machine. Human read­ing error and component calibration are largely eliminated by the digital form of the result. During the period 1944 to 1947 several computers were built which sought to improve the speed of operation through the use of electrical relays as operating elements with the binary system of arithmetic, to which the relays lent themselves through their two state open or closed forms of operation. Numbers were handled in binary form as chains of electrical pulses represent­ing Is and Os in proper sequence.

The first relay machine, completed in 1944, was capable of adding two 23-digit (decimal equivalent) numbers in 0.3 sec, thus materially exceeding the speed of a desk calculator, which is of the order of two 10-digit additions per minute, including time to record the result.

Further increases in operating speed were obtained by application of the electron tube to replace the relay, it being realized that the flip-flop circuit was well suited to such numerical computation in binary numbers. With the flip-flop and certain other circuits it is possible to build an electronic digital computer capable of the usual arithmetic operations at high speeds.

The various forms of electronic digital computers operate, in gene­ral, by principles which parallel the usual numerical methods, and essentially by processes of addition or subtraction. They employ wellknown methods of successive approximation or iteration to achieve interpolation, function values, integration, and the solution of sys­tems of differential and algebraic equations. The pulse lengths em­ployed with the binary numbers vary from a few microseconds to fractions of a microsecond.

Notes

TEXTS (13) 1

(Радіотехніка і комп’ютерна 1

техніка) 1

АРІЙ 1

Radio Engineering 4

Text 1. Electronics 4

Text 2. Electron Emission 4

Text 5. Reception of Radio Signals 7

Text 6. Radio Receivers (I) 8

Text 8. Oscillators 8

Text 11. Detection 9

Text 13. Functions of Vacuum Tubes 10

Text 14. Basic Tube Types 11

Text 22. Bearing 13

Text 23. Transistors, the Basic Mechanism 13

Text 25. Transistor Radio Frequency Amplifiers 15

Text 1. The Computer 15

Text 2. Using the Computer 16

Text 3. Peripheral Equipment 16

Text 4. Computers on Wheels 17

Text 5. Programming a Computer 18

Text 6. The Robot’s Nervous System 19

Text 7. Menu System 19

Text 8. Input, Process, Store, Output 20

Text 10. Memory 22

Text 11. Automatic Translator 23

Text 12. Universal Electronic Computer 23

Text 13. What Is a Digital Computer? 24

Text 14. Digital Computers 24

Text 15. Analog Versus Digital Computers 25

Text 16. Age of Thinking Machines 27

Text 17. General- and Special-Purpose Computers 27

Text 18. Programming 28

Text 19. Types of Instructions 29

Text 20. Simple Hardware, Complicated Logic 30

Text 21. Machine Language and Language Structure 30

Text 23. Mechanical and Electronic Calculating Machines 32

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