What is the symbol of the `mux` chip in C?

Question

I was studying logic gates when I came to know that each logic gate was already defined in C. For example, for the AND logic gate, the symbol is &. For OR, it is |. But I could not find a symbol for the MUX chip.

So, if there is a symbol for MUX, could someone tell me? If there isn't, could someone tell me how to replicate a MUX chip in C?

Answer 1

Closest is the conditional operator: ? :

eg:

 x ? b : a 

if x is 0 you get a if it's 1 (or anything else) you get b

This operator works on entire values, like || && == and ! do. It does not operate on bits as ^ ~ & and | do.

There is no direct equivalent for a multi-input mux. but you can fake one using an anonymous array, eg:

 ((int[]){a,b,c,d,})[x]

but many people frown on constructions of that form.

if you need a bitwise mux you'll need to build it from the bitwise operators eg:

 a ^ (( b ^ a ) & x)

Answer 2

Please be advised that C operates at a much higher level of abstraction than logical gates, so making such comparisons might lead to confusions. That said, the closest you might come to a demultiplexer (I'll start with that since it's simpler) is the left shift operator:

a << b

This expression, assuming that a and b are int expressions, will produce a new int whose bits are the bits of a shifted to the left b times. For example, if a is 0100011011010110 and b is 3, the result will be 0011011010110000. Now, if a is either 0 or 1 and you interpret the resulting integer as being a bus, this corresponds to a demultiplexer.

A multiplexer/selector can be implemented by the right shift operator >>, which shifts bits to the right. However, the result must be &'ed with 1 in order to clear any other bits than the one you were interested in:

(c >> b) & 1

This effectively selects the bit at index b (starting at the least significant bit) from c.

Answer 3

C has four bitwise operators:

• AND, &, as in a & b
• OR, |, as in a | b
• XOR, ^, as in a ^ b
• NOT, ~, as in ~a

There is no MUX operator.

Be careful about your phrasing. These are called bitwise operators, and are analogous to logic gates applied to all bits in an integral type. In C logical operators are different.