SQL * PLUS - setting wrap on for column

Question

hi all, i am playing around with sql plus and i encountered the following problem.
1) is length 10 the default column length for columns with number datatype in sqlplus, i done a select statement and all my column for number have a length of 10
2) why cant i format the length of a number column. i type column empno format 999
although my numbers become #### but "empno" and a length of 10 is still shown at the column name instead of just "emp"
3) how come a column name canot be wrapped
when i set wrap on.
set wrap on
column ename format a3
only the values of ename are wrap
but the column name "ename" isnt wrap
into ena
me
thanks.

Answer 1

Some examples :
TEST@db102 > select 1234567890123 from dual;
1234567890123
   1.2346E+12
TEST@db102 > set numwidth 15
TEST@db102 > /
  1234567890123
  1234567890123
TEST@db102 > col ename for a3 wrapped
TEST@db102 > select ename from emp where empno=7902;
ENA
FOR
D
TEST@db102 > You can find everything in the documentation