M-1092 Nov60

This preliminary interoffice memorandum from November 22, 1960, describes a square root subroutine for the PDP-1 computer. It was supplied to Digital Equipment Corporation (DEC) by Chas. W. Adams Associates, Inc.

The subroutine is designed to calculate the square root of octal numbers ranging from +.000000 to +.377777, with the binary point positioned immediately after the sign bit. For enhanced accuracy, users can scale input numbers by even powers of 2; the resulting square root will have a scale factor that is half of the original scaling factor (e.g., √2⁻⁴A = 2⁻²√A). The subroutine relies on a separate divide subroutine.

To use the subroutine, the address of the number for which the square root is desired is loaded via LIO, followed by a JSP call to the routine's entry point. The document also provides the assembly code listing for the subroutine itself.