Machine features square root extraction using the digit-by-digit algorithm, which uses conditional subtractors to determine each bit of the output and the remainder, to be used in the next unit. Each unit takes 2 bit inputs and compares them to a predetermined number, and subtracts if the inputs are greater than or equal to. Every 2 bits of input is handled by a single subtractor, and each unit produces a one bit output. The subtractors in the unit use ICA addition, with invert B and add 1 (2's complement) subtraction.
There is a 6 bit input in the front of the calculator, labeled "Inputs." The outputs (3 bits and a remainder) are shown in lamps with the MSB of the output labeled "MSB." Simply select the binary number you want to find sqrt() of and it will calculate. It's all combinational, so no start buttons or anything like that.