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A function, f, is a structure with a rectangular footprint whose bottom edge consists a row of input nodes that stores an input value, V, and whose top edge consists of a row of output nodes that stores an output value, f(V):

Function f

The composition of two functions, f(g(V)), comprises f on top of g on top of V, where g’s output nodes serve as f’s input nodes:

Function f of g

Functions employ a standard interface: a row of nodes, evenly spaced, ten columns apart. That interval provides sufficient room for bits to cross or to combine. And a round, base-10 number simplifies measurements during design.

A function’s input and output values have the same bit width and their bits line up. That is, the ith input node shares a common column with the ith output node.

The general-purpose computer contains 8-, 16-, and 24-bit functions. Some of its 16-bit functions interpret the input value, V, as a 2-byte array, [ A, B ], where A and B are the high and low bytes of V, respectively:


Similarly, some of its 24-bit functions interpret the input value, V, as a 3-byte array, [ A, B, C ], where A, B, and C are the high, middle, and low bytes of V, respectively:


One 24-bit function interprets the input value, V, as a two-element array, [ W, C ], where W is a word composed of the high and middle bytes of V, and C is the low byte of V:


A function that accepts an array will return an array of identical dimension.

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