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Section 3

Evolution of HP Calculators

Desk-top calculators present a total computation environment to the user. The syntax and semantics of all the keys are predefined. Individual keystrokes vary widely in power from simple addition to complex I/O operations. Further, support functions such as editing, debugging aids, syntax analyzing, incremental execution, and keyboard monitoring are not only completely defined but also locked into hardware. This is to be contrasted with computer systems whose instruction sets are specified and whose computational environment is defined by ever-evolving multiple layers of software.

This section focuses on the architectures of the Hewlett-Packard series of desk-top calculators, starting with the HP 9100A (c. 1968); its first-generation descendants, the HP 9810/20/30 (c. 1972); and its second-generation descendants, the HP 9815/35/45 (c. 1976). The series span the technology range from discrete components through MSI to LSI in the latest generation. The advances in technology have allowed costs to decrease while allowing functionality to increase. Performance has increased by a factor of 8, operating-system ROM by a factor of 25, and user RAM by a factor of 240. These advances are graphically displayed in Figs. 1 to 4.

These computers represent an unplanned family with no

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