Raise of Opening 1 C/D Bid
What A 1C/D Opening ShowsWhen playing 5-Card Majors, you may have to open 1C or 1D with fewer than 4 cards. Say, with 4=4=3=2 distribution and 14 HCPs, you would usually have to open your longer minor -- Diamonds.
Some people even play that opening 1D shows 4 or more, in which case you would have to open 1C with only 2 cards in the hand above. If you do this, you must Alert and if asked, say: "Could be short." Such an alert is not required when opening a 3-card minor.
In SAYC, open 1D when exactly 4=4=3=2, but bid 1C when 3-3 in the minors, meaning that an opening of 1D will most often show a 4-card or longer suit.
Responding To 1C/1D
(Also see: Inverted Minors.)
Since an opening of 1C can be made with 3 cards, most people like to have 5 cards to raise 1C, although only 4 will do in a pinch.
If you play that an opening of 1D most often shows 4+, then you can comfortably raise 1D with only 4-card support.
In SAYC, you are supposed to bid "up the line", meaning that if you have 4 Diamonds and 4 of a major, you bid 1D first. For people not playing SAYC, bidding the major first seems to be the preferred choice.
If you have a weak hand (6-9 HCPs), you would never bid 1D in response to opener's 1C if you have Club support and no four-card major because you gain nothing by exploring for a minor fit in Diamonds when you have already found a fit in Clubs.
If you play Inverted Minors, raising to the 3 level with a weak hand and 5+ support for partner's minor is even more imperative in order to preempt the opponents.
With more than a minimum, bid your other suit(s) before raising partner, even with 5 or more, in case you have a fit in the majors too.