| Data Fields | |
| char * | key | 
| char * | val | 
| char * | com | 
| char * | lin | 
| int | typ | 
| _keytuple_ * | next | 
| _keytuple_ * | prev | 
| 
 | 
| Value, always as a string | 
| 
 | 
| 
 | 
| 
 | 
| Comment associated to key | 
| 
 | 
| Implemented as a doubly-linked list | 
| 
 | 
| 
 | 
| 
 | 
| Initial line in FITS header if applicable | 
| 
 | 
| Key: unique string in a list |