Sets the current namespace (also known as directory or context). The namespace can be empty, and a new namespace is created when an object is defined in it. The q session prompt indicates the current namespace.

q)\d                  / default namespace
`.
q)\d .o               / change to .o
q.o)\f
`Cols`Columns`FG`Fkey`Gkey`Key`Special..
q.o)\d .              / return to default
q)key`                / lists namespaces other than .z
`q`Q`o`h
q)\d .s               / change to non-existent namespace
q.s)key`              / not yet created
`q`Q`o`h
q.s)a:1               / create object, also creates namespace
q.s)key`
`q`Q`o`h`s