Hi
I like to define a function named myFunction with input parameters a,b,and c

I wrote the function like this

FUNCTION myFunction : INT
VAR_INPUT
a:INT;
b:INT;
c:INT;
END_VAR
VAR
x:INT;
END_VAR

in the function body
I wrote
x:=a+b+c;

when i call the function, I got the output =0, can someone pls help me why I got the answer =0?

my prg is

PROGRAM PLC_PRG
VAR
mycallOutput:INT;
x:INT;
y:INT;
z:INT;

END_VAR

prog:

x:=4;
y:=5;
z:=6;
mycallOutput:=myFunction(x,y,z);

result is mycallOutput =0;

as the function has no idea what the output is you will have to define it.
so your x should be myfunction

I suggest in PRG:

VAR
mycallOutput : INT;
onefunction: myFunction; //POU type of myFunction
END_VAR

in code body:

mycallOutput : = onefunction(x, y, z);

The way you are doing is using a POU type for processing, in fact no function instance is created, so there is output is default 0. Hope Codesys can explain the compiling process. I think the program should not pass compilation.

Yongzhi

FUNCTION myFunction : INT
VAR_INPUT
a:INT;
b:INT;
c:INT;
END_VAR
VAR

END_VAR

in the function body
I wrote
myfunction :=a+b+c; <<<<<<<<<<