Research and Advances
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Character addressable, variable field computers permit ready establishment and manipulation of variable width stacks. Single machine commands may push variable field items down into such stacks or pop them up. The availability of a variety of field delimiters allows the machine to push down or pop up more than one variable width item with one command. Since these stacking operations can be made the basis of compiler decoding algorithms, the proper use of machines of this class for compilation has advantages over machines with fixed-length words.
An automatic data acquisition and inquiry system using disk files
Lockheed Missiles and Space Company has installed a large-scale Automatic Data Acquisition (ADA) system which ties together the Company's manufacturing facilities located in Van Nuys and Sunnyvale, California. The system includes over 200 Remote Input Stations which collect and transmit Company operating data to a central Data Processing Center. Two RCA 301 EDP Systems are used to record and control the flow of data transmitted to the Data Processing Center. A large capacity RCA 366 Data Disc File is used to store information required to provide up-to-date information in response to inquiries received from remotely located Inquiry Stations. In addition to storage of data on the disk files, the system automatically records all incoming and outgoing data on magnetic tape to be used as input to the Company's conventional off-line business data processing applications.
A contour-map program for x-ray crystallography
A FORTRAN program is described for use with the IBM 7090 system and an x, y-plotter to produce a contour map. A matrix of points evenly spaced in each dimension is contoured. Scale factors along the axes may be different and the axes need not be perpendicular.
On the approximate solution of Δ u=F(u)
Three-dimensional Dirichlet problems for &Dgr;u = F(u), Fu ≧ 0, are treated numerically by an exceptionally fast, exceptionally accurate numerical method. Programming details, numerous examples and mathematical theory are supplied. Extension of the method in a natural way to n-dimensional problems is indicated by means of a 4-dimensional example.
M. L. Pei [Comm. ACM 5, 10 (Oct. 1962)] gave an explicit inverse for a matrix of the form M + &dgr;I, where M is an n-square matrix of ones and &dgr; is a nonzero parameter. The eigenvalues of the Pei matrix were given by W. S. LaSor [Comm. ACM 6, 3 (Mar. 1963)]. The eigenvectors may be obtained by considering the system (M+&dgrI)x = &lgr;x, the jth equation of which is S + &dgr;xj = &lgr;xj , (1) where S denotes ∑ni=1 xi. On summing the equations for j = 1, 2, ··· , n, we obtain nS + &dgr;S = &lgr;S. From this we conclude that (a) S = 0 or (b) &lgr; = n + &dgr;.
MIRFAC: a compiler based on standard mathematical notation and plain English
A pilot version of the compiler MIRFAC, now in the operation, is described. The chief features of the system, which is intended for the solution of scientific problems, are the presentation of mathematical formulas entirely in standard textbook notation. The use of plain English for organizational instructions, automatic error diagnosis indicating the actual location of the error in the uncompiled program, and an attempt to minimize that fragmentation of the original problem statement which is a normal feature of programming systems.
Some computer operating systems have a bad habit of inserting tape marks into the output stream willy-nilly. This often results in loss of output when a tape is scratched after its first file has been printed. Other operating systems, notably those recently distributed by IBM for use with the 7090, put tape marks on print tapes only on command, so that frequently a print tape is removed from the computer without any tape mark, and extraneous material is printed.
A semi-iterative process for evaluating arctangents
The technique of obtaining arctangents by inverse interpolation [1] is a relatively long process not suitable for a subroutine. The Taylor series expansion for arguments less than unity converges rather slowly for those near unity. The method of small increments of the argument [2] is again inconvenient for a subroutine. A more rapid series expansion in terms of Chebyshev polynomial [3] is given in terms of a new argument, which is less than 0.1989. This method requires the storage of &pgr;, √2 - 1 and seven coefficients and is perhaps widely used. However, for multiple precision not only the coefficients have to be evaluated to the precision desired, but more must be used. Therefore the following alternative method may prove to be convenient and efficient.
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