There are three major listing formats.  The  default  format
     for  output  directed  to  a  terminal  is multi-column with
     entries sorted down the columns. The -1 option allows single
     column  output and -m enables stream output format. In order
     to determine output formats for the -C, -x, and -m  options,
     ls  uses  an environment variable, COLUMNS, to determine the
     number of character positions available on one output  line.
     If  this  variable  is  not set, the terminfo(4) database is
     used to determine  the  number  of  columns,  based  on  the
     environment  variable,  TERM.  If this information cannot be
     obtained, 80 columns are assumed.