:
                             SWITCHABLE OUTPUT

ZSLIB's switchable output routines allow printing on the console, printing 
on the printer, or printing on both simultaneously.  ZSLIB uses S-series 
routines from SYSLIB to provide this facility, so the switchable output 
routines operate in exactly the same manner as those in SYSLIB.

An external data byte SCTLFL (S control flag) is used to control the 
direction of the output as follows:

     00000000b      00h       no output
     00000001b      01h       console output
     10000000b      80h       printer output
     10000001b      81h       console and printer output

Default output is to the console, if SCTLFL is not initialized.  However, 
if your program is to be re-run with the ZCPR3 GO command, you should 
always initialize SCTLFL to prevent unpredictable results.

SCTLFL should always be declared EXTRN if switchable output is used.

                        SWITCHABLE OUTPUT EXAMPLES

     ld   a,10000000b         ; to printer only
     ld   (sctlfl),a          ; set control flag
     ld   hl,DatBuf           ; point to BCD date buffer
     xor  a                   ; date in American format
     call sdats1              ; print date on printer

     ld   a,10000001b         ; to printer and console
     ld   (sctlfl),a          ; set control flag
     ld   hl,DatBuf           ; point to BCD date buffer
     ld   a,0FFh              ; time in military format
     call stims3              ; print time on both console and printer

     ld   a,00000001b         ; to console only
     ld   (sctlfl),a          ; set control flag
     ld   hl,DatBuf           ; point to BCD date buffer
     call swday1              ; print day of week on console
