| Text | Invalid stack function requested. | 
| Explanation | See Natural Programmer"s Guide for information on available stack functions. | 
| Action | Correct error. | 
| Text | Length of data to be stacked is zero or negative. | 
| Explanation | The length of data to be stacked must be specified as non-zero and positive. | 
| Action | Check program and correct error. | 
| Text | Stack destroyed, command was expected. | 
| Explanation | Natural tried to read a command from the top of the stack, but none was found. | 
| Action | Check program and correct error. | 
| Text | Stack destroyed, data expected. | 
| Explanation | Natural tried to read data from the top of the stack, but no information was available (can be produced by specifying: STACK=(EX pgm:)). Data must be specified for an INPUT statement. If default data are to be passed to INPUT fields, specify data for a non-existent INPUT field. The data will be ignored in delimiter mode. | 
| Action | Check program and correct error. | 
| Text | Stack empty. | 
| Explanation | Natural tried to read data from the stack, but the stack was empty. Either an internal error has occurred, or the stack was destroyed. | 
| Action | Check program and correct error. | 
| Text | Stack data overflow. | 
| Explanation | The amount of stack data does not fit into the stack area. You can stack a maximum of 999 elements. | 
| Action | Check program and reduce the number or size of fields to be stacked. | 
| Text | Invalid UTF-16 data. | 
| Explanation | The data to be stacked do not represent a valid UTF-16 encoding. | 
| Action | Ensure that the length of the UTF-16 character string in bytes is a multiple of 2. | 
| Text | SET KEY error, function key bit not supplied. | 
| Action | Check program and correct error. | 
| Text | SET KEY error, function key not available. | 
| Explanation | The selected function key in a SET KEY statement is not defined to Natural. | 
| Action | Check program and correct error. | 
| Text | Error in SET KEY statement. | 
| Explanation | A variable has been specified after "SET KEY", and the variable contains an invalid value. Valid values are: "PA1" to "PA3", "PF1" to "PF24", "CLR", and "ENTR". This error may also occur if the variable contains "ENTR" but a SET KEY statement option other than the NAMED clause is applied to the key. | 
| Action | Correct error in program. |