Default settings for required arguments in Excel

Function arguments shown in square brackets are optional, meaning these arguments can be left out as demonstrated below.

=LEFT(text,[num_chars])

=LEFT("Rick") 

Here, the second argument is omitted, so the function defaults to 1 for the number of characters.

As a result, it returns "R".

You can also include a comma after the first argument and leave out the second, like this:

=LEFT("Rick",)

In this case, the function treats the number of characters as 0, so the output is "" (a zero-length text string). 

Now, what if the first argument is ignored?

=LEFT(,)

This also returns an empty string.

For mandatory arguments, if nothing is provided:

• If a text value is expected, the function uses ""

• If a number is expected, it uses 0

This behavior applies to most, but not all, functions. 

Examples include:

=FIND(,)

=SUBSTITUTE(,,)

=MID(,1,)

Note: In the MID function, the start number argument typically begins at 1. Ignoring it causes the function to treat it as 0, which results in an error.

=REPT(,)

=TEXT(,)