> For the complete documentation index, see [llms.txt](https://trizen.gitbook.io/perl6-rosettacode/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://trizen.gitbook.io/perl6-rosettacode/programming_tasks/m/memory_layout_of_a_data_structure.md).

# Memory layout of a data structure

The following is specced to work, but implementation of shaped arrays is not quite complete.

```perl
enum T_RS232 <
    carrier_detect
    received_data
    transmitted_data
    data_terminal_ready
    signal_ground
    data_set_ready
    request_to_send
    clear_to_send
    ring_indicator
>;

my bit @signal[T_RS232];

@signal[signal_ground] = 1;
```

In the absence of shaped arrays, you can do the usual bit-twiddling tricks on a native integer of sufficient size. (Such an integer could presumably be mapped directly to a device register.)

```perl
$signal +|= 1 +< signal_ground;
```

Using a native int is likelier to work on a big-endian machine in any case. Another almost-there solution is the mapping of C representational types into Raku for native interfaces, but it does not yet support bit fields.