C Control The I Unit-M Advanced 5 Vdc Inputs / outputs 16 x digital I/Os / 8 x analogue or digital I/Os Program memory 2 198805 Datenbogen

Internal organisation 
While the C-Control usually has just BYTE and WORD Types, even for non professionals easy to handle, 
now there is the new Data Type Float. It consists on one byte exponent and 3 byte mantissa with sign. 
Therefore a floating point value occupies 4 bytes (32 bit). 
 
Value size 
The flaoting point Module is able to compute values in the range of  +-1 × 10±38.  
 
Accuracy 
You will find that even simple values can not be expressed 100% accurate with a 32bit Floating Point 
System. The value 1234 will be shown as 1233.999, but this is not a computing error. It is based on the 
limited accuracy of every 32 bit Floating Point System.  

For simple calculations it is not required to know this details. But very complex computations may lead to 
stack overflows if some basics are not considered.  
The C-Control Stack 
The stack is a memory used for temporary storage of values. This can be values needed for calculations or 
addresses, needed for a return from a subroutine.  
 
For a brief information of stack usage see this example:  
 
MyFloat=FloatVar1*Floatvar2 
 
This expression is compiled to a token code that causes the operating system to do the following: 

 

 
 
 
 
 
 
 

If the term is more complex, many values will be pushed to stack before any calculation is done and they are 
removed from stack. 
 
Example: 
MyFloat=Floatvar3-FloatVar1*(Floatvar2+Floatvar4) 
 

 
   

 
 
 
 
 
 
 
 
 
 
 
 
 

 
You can see that even this simple term pushes 4 float values to stack, before calculation is done and values 
are removed from stack. Here 16 Bytes Stack are used for this simple term. And remember that a subroutine 
call also adds two bytes return address to stack.