Nested structures

// declare struct type for a single point
typedef struct {
    float x;
    float y;
} point;

// declare a struct type for a line with a start and end point
typedef struct {
    point start;
    point end;
} line;

int main(void) {
    line l;

    l.start.x = 3.5;
    l.start.y = 8.4;
    l.end.x = 12.7;
    l.end.y = 18.5;
    ...
}