A constant function outputs the same value regardless of its input:

f(x) = k

A 1-bit function that always returns 0 is realized by XORing the input with itself:

f(A) = A ⊕ A = 0

The code below links both inputs of an XOR gate withÂ a horizontal I-tetromino.

false.tih 0xor 0 1in i -2..1 0out o -2..1 12

The tests in the following image affirm the circuit consistently outputs 0.

A 1-bit function that always returns 1 is realized by XNORing the input with itself:

f(A) = A ⊕ A = 1

A horizontal I-tetromino joins the inputs of an XNOR gate in the code below.

true.tih 0xnor 0 1in i -2..1 0out o -1..1 17

The following image reveals the circuit invariably yields 1.

A constant byte function is an assemblage of eight 1-bit constant functions. The image below depicts the constant byte function f(x) = 0 for an arbitrary input value.