Calculators sold by Sumlock and made by other companies
Sumlock Compucorp 400 Series

Sumlock Compucorp 425G Scientist

Compucorp 425G Scientist

By Daniel Sancho from Málaga, Spain (Compucorp 425G) [CC BY 2.0  (], via Wikimedia Commons

Sumlock-Compucorp 400 Series

The Sumlock-Compucorp 400 Series comprise several versions of the 425 Scientist and 445 Statistician models, which are highly capable desktop, programmable, printing, scientific and statistics calculators, with a magnetic card reader/writer.

In January 1973 the journal Electronics Today International reported[1]:
    "The Sumlock Compucorp 400 Series comprises a choice of desk-top programmable printing calculators of greatly enhanced power and flexibilty.  A choice is available from models of increasing capacity and power, in terms of data storage and programme steps.  The model 425 for general scientific, engineering and surveying users progress from Model 425-11 with data stores [sic] and 512 programme steps, through model 425-22 with 138 data stores and 1024 programme steps, and model 425-44 with 266 data stores and 2048 programme steps to Model 425-88 with 522 data stores and 4096 programme steps
    Model 445 for statistical applications offers the same choice of data storage and programme steps.
    Other characteristics include: Full 4 rule arithmetic, and ax operates into and out of all data stores.  The machines can be programmed from the keyboard, and full programme printout capability simplifies editing.  Under programme control, memory and programme storage can be intermixed to obtain an ultimate of more than 1,000 data storage registers or 8,000 programme steps.
    425 Models offer input/output in degree-minutes-seconds, full 4-quadrant co-ordinate conversion, radian to degree conversion statistical summation (n, x, x2), standard deviation and mean, factorial, sum-square backout for correction of summations, degree/grad operation, and trigonometric functions.
    Model 445 statistical machines contain labelled keys for single and grouped summations, standard deviation and mean, paired-data summations, linear regression and independent and dependent tests.
    The user can accumulate three sets of summations at once and the machine will automatically calculate linear regression for up to 3 variables.  A key permits removal of unwanted data from summations.
    There are keyboard functions for chi-square statistics (observed and expected frequencies), Z-statistics, permutations and combinations, normal probability, factorial, standard deviation using the n formula, and predicted values.
    Keyboard arithmetic is fully algebraic, with nesting of parentheses.
    Most equations can be entered in natural order as they are written.
    Keys are buffered so that the user can continue entering data while the machine is calculating.
    The 400 Series machines will interface with a variety of peripherals—input/output typewriter, XY plotter, mark-sense/punched card reader, tape cassette recorder, Teletype."


Made in the U.S.A. by Compucorp (Computer Design Corporation) of Los Angeles, and supplied as the OEM to Sumlock Anita Electronics Ltd.



  1. "Equipment News: Sumlock Compucorp Calculators", Electronics Today International, January 1973, p76.

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