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The IBM 1401 is a transistorized data-processing computer introduced in 1959, used for business workloads involving punched cards, printing and magnetic tape. Its stored programs transformed records and coordinated input/output devices, making it a historically important example of computing organized around data processing.^[ref]

It also provides a concrete scientific-computing benchmark. Bresenham reported a 333-core-location IBM 1401 program controlling an IBM 1627 Plotter, with approximately1.5 milliseconds of computation between successive plotted increments.^[ref] The report connects an algorithm's arithmetic choices to actual program storage and timing. These are measurements for that implementation and task, rather than universal instruction timings for every 1401 program.

The IBM 1627 is a digital plotter controlled by a computer, producing drawings through incremental pen motions on a coordinate grid. A sequence of horizontal, vertical or diagonal steps approximates a line while pen control separates drawing from repositioning.

Bresenham's 1965 paper reports an IBM 1401 program controlling an IBM 1627. It used 333 core locations and averaged approximately1.5 milliseconds of computation between successive increments.^[ref] The algorithm chooses between neighboring grid moves using an incrementally updated integer decision value, avoiding multiplication or division in the main stepping process. The device therefore illustrates how a geometric approximation becomes a sequence of physical control pulses, with both computational cost and mechanical resolution relevant.

A plotter is a computer-controlled drawing device that produces physical marks by moving a pen or another marking tool relative to a surface. Geometric commands become motions and pen-up or pen-down actions. In a digital stepping plotter, available moves impose a coordinate mesh, so a mathematical line must be approximated by legal steps.

Jack Elton Bresenham's 1965 paper describes a plotter with eight possible neighbor moves, typically on a mesh spaced one hundredth of an inch apart.^[ref] For a segment from $(0,0)$ to $(5,2)$, the controller must distribute two upward increments among five rightward increments. Bresenham's line algorithm updates an integer decision value to choose successive moves. This connects computational geometry to an apparatus whose resolution and permitted motions determine the drawing.