Circuit for detecting the position of an extreme "1" bit in a binary number

Apparatus for detecting the "1" bit of an input binary number of n-bits having an extreme position in that number and for producing an output representing that position, the apparatus including a binary tree of two-input OR-gate means having m stages, where 2.sup.m .gtoreq.n, with or without the final stage of the tree containing a single OR-gate means, and having a first stage with up to 2.sup.m-1 OR-gate means to the inputs of which the bits of the input number are respectively applied, and a multiplexer circuit having m-2 multiplexer trees selectively responsive to inputs to and outputs from the stages of the binary tree to produce respective output bits which in combination with an output from the penultimate stage of the binary tree form a binary number representing the position of the extreme "1" bit in the input number.