The HP 9100B Calculator

The HP 9100 Computing Calculator

The model 9100A is introduced in the September, 1968, Hewlett-Packard Journal and appears for the first time in the 1969 catalog, page 130 with the following description:

The 9100A is a programmable, electronic calculator which performs operations commonly encountered in scientific and engineering problems. Its log and trig functions are each performed with a single key stroke, providing fast, convenient solutions to intricate equations. Computer-like memory enables the calculator to store instructions and constants for iterative solutions. The easily-readable cathode ray tube instantly displays entries, answers and, when desired, intermediate results.

Direct keyboard operations include: Arithmetic, Logarithmic, Trigonometric, Hyperbolic and Coordinate transformation. Decimal point is selectable, fixed or floating-point notation for display of entries or answers. A decimal wheel selects 0-9 decimal places, with automatic rounding to the number of places selected.

Magnetic core memory contains 19 registers: 3 displays registers (keyboard, accumulator, temporary) and 16 storage registers, with store/retrieve controls. These registers may be used to store 16 constants, or 196 program steps plus 2 constants, or a combination of constants and program steps. The read-only memory contains over 32,000 bits of fixed information for keyboard routines.

Programming: The program mode allows entry of program instructions, via the keyboard, into program memory. Programming consists of pressing keys in the proper sequence, and any key on the keyboard is available as a program step. Program capacity is 196 steps. No language or code-conversions are required. A self-contained magnetic card reader/recorder records programs for program memory onto wallet-size magnetic cards for storage. It also reads programs from cards into program memory for repetitive use. Two programs of 196 steps each may be recorded on every reusable card. Cards may cascaded for longer programs.

Speed: Maximum times for total performance of typical operations, including decimal-point placement:

Add, substract: 2 milliseconds. Multiply: 22 milliseconds. Divide: 27 milliseconds. Square-root: 30 milliseconds.
Sin, cos, tan: 330 milliseconds. ln x: 130 milliseconds. Coordinate transformation: 280 milliseconds.

It is interesting to note that computer performance of this size was state-of-the-art just one year before the first moon landing.

Price: $4900. (Average cost of a new car in the USA in 1968 was $2800)

The HP 9100B Calculator with 9120A Printer

The 9100, Versions & Accessories

The HP 9100A was introduced first in 1968 with maximums of 16 storage registers and 196 program steps.

The HP 9100B, in 1970 doubles this capacity with maximums of 32 storage registers and 392 program steps. On both machines, core was shared between registers and program steps. (The 9100B had two pages of core.) The HP 9100B also added subroutines, a dual program display, and a key to recall numbered registers into X.

The HP 9101A Extended Memory, is introduced in the 1971 catalog supplement. It is a rack mountable box of core memory providing an additional 3472 program steps or 248 data registers. This option could be added to either model.

The Model 9120A Printer, shown on the above photo, attaches to the top of the calculator. It is introduced in late 1969 for use with the 9100A and remains compatible with the 9100B version. The 9120A, electrostatic printer, prints the contents of display registers X, Y, Z, singly or in any combination, upon manual or programmed command.