1. A computer program product for executing an extended translate and test instruction, the computer program product comprising: a storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising: executing the extended translate and test instruction, the executing comprising: obtaining an argument character; i. determining whether a value of the argument character has a particular relationship with respect to a predefined size, and based on the value having the particular relationship, using a predefined value for a function code for the argument character, and based on the value not having the particular relationship, using the argument character as an index into a function code data structure to locate a function code corresponding to the argument character; and ii. based on said function code being a first value, storing said function code in a register; or iii. based on said function code being a second value, obtaining a next argument character and repeating steps i through iii, unless an ending condition exists.