ThinBASIC Core Language > Data types and variables > TYPE (or UDT User Defined Types) > UDT (User Defined Types) > Memory representation

Element alignment

By default, the elements are tightly packed in memory, one after each other.

You can alter this behaviour by specifying alignment modifier. It can take 3 different values:

1.byte, for 1 byte alignment

2.word, for 2 byte alignment

3.dword, for 4 byte alignment

The default packing is on byte level, so you don't really need to specify it.

In case you want to pack values aligned to 4 byte steps, you might consider using DWORD modifier.

Let's have a look at this example:

TYPE RGBColor
  R AS BYTE
  G AS BYTE
  B AS BYTE
END TYPE

By default, the size of RGBColor will be 3 bytes, as you can verify with SizeOf:

msgBox SizeOf(RGBColor)

3 elements, each 1 byte in size.

To apply 32bit alignment, use DWORD modifier:

TYPE DwordAlignedRGBColor DWORD
  R AS BYTE
  G AS BYTE
  B AS BYTE
END TYPE

This means that R, G and B elements will still be of byte data type, however their element offset will change to 4 byte jumps.

You can verify it easily:

DIM colorNormal  AS RGBColor

msgbox strFormat$("The offset of .R is {1}, .G is {2} and .B is {3}",
                  UDT_ElementOffset(colorNormal.r),
                  UDT_ElementOffset(colorNormal.g),
                  UDT_ElementOffset(colorNormal.b))

DIM colorAligned AS DwordAlignedRGBColor

msgbox strFormat$("The offset of .R is {1}, .G is {2} and .B is {3}",
                  UDT_ElementOffset(colorAligned.r),
                  UDT_ElementOffset(colorAligned.g),
                  UDT_ElementOffset(colorAligned.b))

Element packing

Element packing