MCLOCK — Time function
clock(3) in the C standard library.
This intrinsic is not fully portable, such as to systems with 32-bit
INTEGER types but supporting times wider than 32 bits. Therefore,
the values returned by this intrinsic might be, or become, negative, or
numerically less than previous values, during a single run of the
compiled program.
RESULT = MCLOCK()
INTEGER(4), equal to the
number of clock ticks since the start of the process, or -1 if
the system does not support clock(3).