Assign a value to a global variable
Persist an object as a file or directory

nam set y                  set[nam;y]                     / set global variable nam
fil set y                  set[fil;y]                     / serialize y to fil
dir set t                  set[dir;t]                     / splay t to dir
(fil;lbs;alg;lvl) set y    set[(fil;lbs;alg;lvl);y]       / write y to fil, compressed
(dir;lbs;alg;lvl) set t    set[(dir;lbs;alg;lvl);t]       / splay t to dir, compressed
(dir;dic) set t            set[(dir;dic);t]               / splay t to dir, compressed

Where

alg   integer atom     compression algorithm
dic   dictionary       compression specifications
dir   filesymbol       directory in the filesystem
fil   filesymbol       file in the filesystem
lbs   integer atom     logical block size
lvl   integer atom     compression level
nam   symbol atom      valid q name
t     table
y     (any)            any q object