# What does the square brackets mean?

In this diagram:

What does the S[2:0] mean? I think it is the state but why is the state in 3 bits? What does the 2 and 0 mean?

Cheers!

• "2 and 0" (as in [2:0]) means "from the bit numbered 2 downto the bit numbered 0." So it means three bits that are numbered sequentially from 0 to 2 (or 2 to 0.) S[2:0] means S2, S1, and S0. S'[2:0] means S'2, S'1, and S'0. It is short-hand notation. – jonk Jan 24 '18 at 7:35
• It means three bits ordered like $S_2S_1S_0$ where $S_2$ is the MSB and $S_0$ the LSB. – dirac16 Jan 24 '18 at 7:38

[2:0] is a notation borrowed from Verilog. It means that the signal is a bus containing multiple bits, numbered from 2 down to 0 -- three bits in total.