All DB-Library/C applications require these header files:
sybfront.h – defines symbolic constants, such as function return values (described in the Open Client DB-Library/C Reference Manual) and the exit values STDEXIT and ERREXIT. sybfront.h includes type definitions for datatypes that can be used in declaring program variables.
sybdb.h – contains additional definitions and type definitions. Most of these are meant to be used only by DB-Library/C routines. Use the contents of sybdb.h only as documented in the Open Client DB-Library/C Reference Manual.
syberror.h – contains error severity values and should be included if the program refers to those values.
See the Open Client DB-Library/C Reference Manual for more information on header files.