ACOL
ACOL is one of the oldest bidding systems. 4-card suits are bid up the line. The main problem lies with the vague major suit openings. The strong two openings also waste valuable space.
Opening bids
1
12
+
HCP, 4
+
1
12
+
HCP, 4
+
1
12
+
HCP, 4
+
1
12
+
HCP, 5
+
or 15
+
4
3
3
3
1NT
12 - 14 balanced
2
GF or 23
+
balanced
2
SemiForcing
2
SemiForcing
2
SemiForcing
2NT
20 - 22 balanced