Why does byte writing to a file from VBA add 1100 to each byte?

I am trying to copy an image as a byte array to a file in vba.

The first three bytes of the file, represented as a byte array:

   Dim arr(3) As Byte arr = {23,21,2f}

The code that copies from an array to a new file is:

Open "try444.jpg" For Binary As #1

For cnt = 1 To UBound(arr)

    Put #1, LOF(1) + 1, arr(cnt)

Next

but it writes 1100 2311 0023 1100 2111 002f 1100 to the file (all in hex)

What is wrong with my code?

Solution

because arr is being redefined somewhere. If I write the procedure as a single function:

Option Explicit
Sub test()
Dim cnt As Long
Dim arr(3) As Byte

arr(1) = &H23
arr(2) = &H21
arr(3) = &H2F

Open "try444.jpg" For Binary As #1

For cnt = 1 To UBound(arr)

    Put #1, LOF(1) + 1, arr(cnt)

Next
Close #1

End Sub

then I get exactly the bytes you would expect 23 21 2F

If I neglect to define the type (or I don't have Option Explicit) then it becomes a variant, and then it's anyone's guess as to what will appear, as the variant datatype includes a type code. (in my case, I get 02 00 23 00 02 00 21 00 02 00 2f 00)