Appendix E: Messages and Errors256
  An attempt was made to execute a specific print function when the printer was not connected to the system.
NULL  Keystroke was nullified by holding the key down for longer than about half a second.
PRIVATE  Refer to the owner’s handbook provided with the HP 82104A Card Reader.
  An attempt was made to view a private program.
OUT OF RANGE  A number has exceeded the computational or storage capability of the HP-41C.
 
Overflow = ± 9.999999999 99
SDEV  where the standard deviation of x (Sx = √(M / [ n(n–1)]) or y (Sy = √(N / [ n(n–1)]) results in division by zero or the square root of a negative number. (M = nΣx2 – (Σx)2; N = nΣy2 – (Σy)2.)
FACT  where x > 69.
PACKING  Program memory is being packed.
TRY AGAIN  As a result of a packing operation, the last keystroke sequence must be repeated. This could be an XEQ , ASN , GTO · · , or when an attempt is made to insert an instruction into a program.
YES  The answer to flag test when test is true. Also the answer to conditionals when relationship between x and 0 or y is true.
NO  The answer to flag test when test is false. Also the answer to conditionals when relationship between x and 0 or y is false.
RAM  An attempt was made to COPY a program in RAM (random access memory—a memory module, or internal memory) to RAM.
ROM  An attempt was made to DEL , CLP ,    , or insert into a program that is currently in ROM (read only memory—an application module).