Random Ladder Logic Programming Question

Hey guys,

I am replicating an old ladder logic program recently.

And I have some questions, I am not sure these logic was made for a purpose or just the previous engineer's habit.

1. All the real variable, it use int type and multiple by 10.
For instance, the temperature set point is 212.0 Fahrenheit, in the program, you would see 2120, the last 0 is the tenths after decimal point.

However, the program has real number type, I dont understand why can we use real number.

2. I saw some output as a relay to energize the same output coil.
which looks like this:

   out1              out1  

----||----------------()------

no other relay is link to this out1, should this out1 be always off?
I guess this output is abandoned, right?

What do you guys think?

Common to do this in older proc that use serial radio or other slow link. Integer Registers are a single register and a float (REAL) takes 2 registers.

I can't see how the second rung is useful.

-| |--( )- gives you a view of the output in your code. So you could right click it and hit toggle, for example.
If I saw that I would be 95% confident that "nothing writes to the output." Confidence would go up, if I knew the programmer. (Or down I guess, depending on who the programmer is)

It is also significantly faster for an old CPU to do 16 bit integer math (2120+320)*5/9 than it is to do floating point math (212.0+32.0)/1.8
You are also clear on your accuracy with INT. Floating point has issues with 0 Vs "about zero".
Also for a given old school protocol, 16bit is nearly twice as fast to send as 32bit float.
The modbus standard does not have floats (or at least it didn't)