sc_code will contain the results of the last library function call
executed. Errors are indicated by negative numbers, warnings by positive
numbers greater than zero, and a zero indicates success. Most functions in
the library will NOT execute if sc_code contains an error. Because
the functions will not operate on errant information, this feature provides
a small measure of security for your data.

During program debug it may be advantageous to print the text message
associated with the contents of sc_code. scemsg will return the
address of the message associated with the contents of sc_code, which
can then be printed by puts.

If you desire to clear an error or warning condition either the global
variable sc_code can be set to zero or the function sceclr can be
used. It is preferable to use the function rather than the global variable.