1. A method of executing a machine instruction in a central processing unit, the method comprising: obtaining, by a processor, a machine instruction for execution, the machine instruction being defined for computer execution according to a computer architecture, the machine instruction comprising: at least one opcode field to provide an opcode, the opcode identifying a Vector Find Element Not Equal operation; an extension field to be used in designating one or more registers; a first register field to designate a first register, the first register comprising a first operand; a second register field to designate a second register, the second register comprising a second operand; a third register field to designate a third register, the third register comprising a third operand; and a mask field, the mask field comprising one or more controls to be used during execution of the machine instruction; and executing the machine instruction, the execution comprising: identifying the first register based on a combination of the first register field and a first portion of the extension field, identifying the second register based on a combination of the second register field and a second portion of the extension field, and identifying the third register based on a combination of the third register field and a third portion of the extension field; searching the second operand for a zero element, wherein the searching the second operand for a zero element finds a zero element at a first byte position and the searching provides a null index set to a value that is a byte position of a sequentially-first zero element found in the search; comparing one or more elements of the second operand with one or more elements of the third operand for inequality, wherein the comparing finds an unequal element at a second byte position and the comparing provides a compare index separate from the null index, the compare index being set to a value that is a byte position of a sequentially-first unequal element; and selecting between the null index and the compare index to provide a result of executing the machine instruction, the result being the null index or the compare index and being a value of a byte position of a sequentially-first zero or unequal element or a value indicating a size of the second operand, and the selecting being based on whether an unequal element or zero element is found, wherein the selecting selects the lesser of the first byte position and the second byte position.