kdb provides the following functions/variables within the .Q namespace:

Common .Q Functions

.Q.fFormats a number similar to the printf command with a .%.2f argument.
.Q.fmtFormats a number to a fixed number of characters and dp.
.Q.sFormat an object to plain text (used by the q console, obeys \\c setting
.Q.addrip-address as an integer from a hostname symbol
.Q.hosthostname as a symbol for an integer ip-address
.Q.fcparallel on cut
.Q.fsLoops over file (in chunks) applying function
.Q.gcInvokes the garbage collector.

Disk Storage .Q Functions

.Q.cnnumber of rows for partitioned table passed by value
.Q.pnPartition counts cached since the last time .Q.cn was called
 Saves a table splayed to a specific partition of a database sorted (`p#) on a specified field
.Q.en.Q.en[`:db; table]
 Enumerates any character columns in a table to sym and appends any new entries to a file in the db directory.
.Q.hdpf.Q.hdpf[historicalport;directory;partition;`p#field] save all tables and notify host

Missing or Empty Tables - .Q Functions

.Q.chkfills missing tables
.Q.vpdictionary detailing which tables have missing partitions
.Q.bvfunction that can be called to build the dictionary

Partitioned Tables - .Q Functions

.Q.qtReturns 1b if x is a table, 0b otherwise.
.Q.qpReturns 1b if given a partitioned table, 0b if splayed table, else 0
.Q.indit takes a partitioned table and (long!) indices into the table
.Q.PVIn partitioned dbs, contains a list of partition values - conformant to date
.Q.pv.Q.PV as modified by .Q.view.
.Q.viewset a subview eg .Q.view 2#date