Скачать или смотреть Module 1. Day 3. Formal and Actual Parameters

In the previous chapters we discussed two types of methods (procedures and functions). Let’s consider a piece of code we have worked with before.

Here we call our function that passes parameters SecondNumber, ThirdNumber, and FourthNumber. As you can see, inside the function we use different parameters LowerBound, UpperBound, and BigNumber. So, what is the difference?

Formal parameters are parameters of procedures or functions. They are created and used only inside functions with values matching values of actual parameters.

Actual parameters are values that are passed to a procedure or function.

The concept is that formal parameters exist only inside the created function. They are created at the start of a function and get deleted at the end of such a function (or a procedure, of course). So, SecondNumber and LowerBound are actually two different variables that share the same value.
We can pass actual parameters to functions or procedures by value or reference (remember about [Val] keyword). Let’s check the difference between these two options.
Here we pass actual parameter ActualParameter1 as a value. So, any changes to formal parameter FormalParam1 do not affect the actual parameter.

This was a scenario for passing a parameter by value using keyword [Val]. Now consider the following code.

And here we passed actual parameter ActualParameter1 by reference. It means that now changes in the formal parameter impact the actual parameter. Here is the result.

As you can see, passing actual parameters by reference leads to irreversible changes of the ActualParameter1. So, we recommend that you be extremely careful when passing parameters to functions and procedures.
Also, the meaning of term reference in the 1C language is different as compared to any other programming language. We do not have references to variables in 1C, and in all future cases (apart from passing parameters) by reference we mean references to configurations objects. And this is the topic for future discussion.