An ideal scalar loop must satisfy measurement, error, command, and output together. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
All loop values must agree at once
With target 8 volts and forward gain 3, the checked output is 6 volts.
y=6V,m=6V
The command equals the ideal output
The measured value is 6 volts, the error is 2 volts, and gain 3 gives command 6 volts.