This program sets your X servers root window name as the current time in 12-hour binary. This allows dwm to use it in their status bar. Other window managers may also use this string for something. I use it with dwm as a clock to practice recognising binary numbers quickly.
-d: display time in decimal format (HH:MM)
-m: Use the 24-hour time format
cc binstatus.c -lX11 -o binstatus
You may prefer to put this in your .xinitrc file and move the binary to somewhere like /usr/bin.