The fonts must first be organized into a list in memory, a process called “registering.” Register fonts by calling the function _registerfonts. This function reads header information from specified .FON files, building a list of file information but not reading any mapping data from the files.
The GRAPH.H file prototypes the _registerfonts function as
short far _registerfonts( unsigned char far * );
The argument points to a string containing a filename. The filename is the name of the .FON file for the desired font. The filename can include wild cards, allowing you to register several fonts with one call to _registerfonts.
If it successfully reads one or more .FON files, _registerfonts returns the number of fonts. If the function fails, it returns a negative error code.