Execution of a machine instruction in a central processing unit. A perform floating-point operation instruction and a test bit are obtained. If the test bit has a first value, a specified floating-point operation function is performed, and a condition code is set to a value determined by the specified function. If the test bit has a second value, a check is made to determine if the specified function is valid and installed on the machine. If the specified function is valid and installed on the machine, the condition code is set to one code value, and if the specified function is either not valid or not installed on the machine, the condition code is set to a second code value.