Oracle SQL: Why are column headers missing? I want to understand why my columns are missing their headers.

Consider this table:

SQL&gt; DESC customer;

Name         Null?    Type         
------------ -------- ------------ 
CUST_ID      NOT NULL NUMBER(5)    
CUST_NAME             VARCHAR2(15) 
ACCOUNT_ID            VARCHAR2(10) 
ACCOUNT_TYPE          VARCHAR2(2)  
STATE                 VARCHAR2(2)  


When I select * from the table, the result is missing the column headers.

SQL&gt; SELECT * FROM customer;

     90001 B and B         A-11101    PR AK
     90002 XYZ             A-11102    CM NJ
     90003 JJ Sons         A-11103    CM NJ
     90004 Exxon           A-11104    PR NY
     90005 ABC             A-11105    CM NY
     90006 Smith Co.       A-11106    CM MD
     90007 Brown Co.       A-11107    CM MD
     90008 Cooper Inc.     A-11108    PR MD

8 rows selected. 


Why?

My goal is to display the tables with the headers. If there are other details I need to add, let me know.
Heading may be disabled in your environment. Enable it (it is enabled by default).

SQL&gt; select banner from v$version;

Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
PL/SQL Release 12.1.0.2.0 - Production
CORE    12.1.0.2.0      Production
TNS for Linux: Version 12.1.0.2.0 - Production
NLSRTL Version 12.1.0.2.0 - Production

SQL&gt; show heading
heading OFF
SQL&gt; set heading on
SQL&gt; select banner from v$version;

BANNER
--------------------------------------------------------------------------------
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
PL/SQL Release 12.1.0.2.0 - Production
CORE    12.1.0.2.0      Production
TNS for Linux: Version 12.1.0.2.0 - Production
NLSRTL Version 12.1.0.2.0 - Production


Or pagesize is set 0:

SQL&gt; show heading pagesize
heading ON
pagesize 14
SQL&gt; set pagesize 0
SQL&gt; select banner from v$version;
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
PL/SQL Release 12.1.0.2.0 - Production
CORE    12.1.0.2.0      Production
TNS for Linux: Version 12.1.0.2.0 - Production
NLSRTL Version 12.1.0.2.0 - Production

SQL&gt; set pagesize 14
SQL&gt; select banner from v$version;

BANNER
--------------------------------------------------------------------------------
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
PL/SQL Release 12.1.0.2.0 - Production
CORE    12.1.0.2.0      Production
TNS for Linux: Version 12.1.0.2.0 - Production
NLSRTL Version 12.1.0.2.0 - Production