Radio Shack TRS-80 Model II Reference Manual page 45

Model II TRSDOS
CLOCK
Turn on Clock-Display
This command controls the real-time clock display in the upper right corner of
the Video Display. When it is on, the 24-hour time will be displayed and
updated once each second, regardless of what program is executing.
TRSDOS
starts up with the clock off.
Note: The real-time clock is always running, regardless of whether the clock-
display is on or off.
Examples
CLOO';;
Turns on the clock-display.
CLOO, OFF
Turns off the clock-display.
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