This structure is a 4-byte structure. The colon indicates the meaning of the bit field, that is, which bits of this structure are accessed when accessing the current variable name.

uint 16 rsvd 1:3； // 2:0 Reserved

It is defined that the value returned when accessing the member variable rsvd 1 using the structure consists of 0: 2 bits of the whole 4-byte structure; Your structure defines what each bit of the 32-bit status register of a CPU stands for, and rsvd 1 means that the first three bits are reserved for later use;

The structure maps the 32 bits of cpu into a bit domain structure, which is more convenient for programs to access every bit of the register than shift operation.