Suppose four names belong together, but each needs a meaningful label. A `struct birdStruct` can give them members named `jay`, `magpie`, `raven`, and `chough`; `aName.raven` then selects one member without relying on an array index. section 6.3
struct birdStruct {
char const* jay;
char const* magpie;
char const* raven;
char const* chough;
};
struct birdStruct const aName = {
.chough = "Henry",
.raven = "Lissy",
.magpie = "Frau",
.jay = "Joe",
};
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Read the type declaration first, then the separate definition of `aName`. The initializer names each member with a leading dot, regardless of its position in the declaration. section 6.3
TAKEAWAY: A `struct` is an aggregate whose named members can have different types. Arrays instead group elements of one base type, where a first, second, and subsequent element make sense. Declaring a structure type describes that type; it does not by itself declare an object. Member declarations resemble ordinary variable declarations, and `.` selects a member of a structure object. In the bird example, the members refer to strings; the strings themselves are not part of the structure. section 6.3 section 6.0
Calendar fields
An array of calendar values leaves a question: which index holds the year? `struct tm` gives fields names such as `tm_year`, `tm_mon`, and `tm_mday`. A designated initializer sets those fields explicitly; the illustrated date uses `2019-1900` for `tm_year` and `4-1` for `tm_mon`. Code can then read `today.tm_year` and add 1900 when displaying the year. A function can receive a `struct tm`, change its `tm_yday` member, and return the resulting structure. section 6.3
Structures can also be members of other structures: a person can contain a date structure, which in turn contains calendar and precision fields. When code instead has a pointer to a structure, `->` selects a member of the pointed-to object: `a->tv_sec` means `(*a).tv_sec`. The selected member is the member object, not necessarily another pointer. section 6.3 section 11.2
