PROGRAM FILE 18: THE IF-THEN STATEMENT WITH STRING OPERANDS.                    
    ANSI STANDARD 10.2, 10.4                                                    
                                                                                
SECTION 18.1: THE IF-THEN STATEMENT WITH STRING OPERANDS.                       
                                                                                
THIS SECTION TESTS THE COMPARISON OF STRING VARIABLES AND                       
CONSTANTS WITH A VARIETY OF VALUES. BOTH RELATIONSHIPS                          
(= AND <>) ARE TESTED FOR EACH PAIR OF VALUES. THE 'V' OR                       
'C' FOLLOWING THE COMPARAND VALUE INDICATES WHETHER IT IS                       
A VARIABLE OR A CONSTANTS.                                                      
                                                                                
'T' OR 'F' IS PRINTED TO SHOW THE OUTCOME OF THE                                
COMPARISON. FOR INCORRECT COMPARES, AN '*' IS PRINTED                           
NEXT TO THE ERRONEOUS RESULT.  WHEN DISPLAYING COMPARAND                        
VALUES, THE UNDERLINE CHARACTER, '_', IS USED TO REPRESENT                      
THE SPACE CHARACTER (THUS A DISPLAYED 'ONE_BLANK'                               
INDICATES AN INTERNAL VALUE OF 'ONE BLANK').                                    
ALSO, THE NULL STRING (LENGTH OF ZERO) IS DENOTED BY THE                        
LABEL '(NULL STRING)'.                                                          
                                                                                
CHARACTER STRINGS SHOULD TEST EQUAL IF AND ONLY IF THE                          
STRINGS ARE EQUAL IN LENGTH AND CONTAIN IDENTICAL SEQUENCES                     
OF CHARACTERS.                                                                  
                                                                                
                  BEGIN TEST.                                                   
                                                                                
LEFT                 : RIGHT                                                    
COMPARAND         V/C: COMPARAND         V/C  =   <>  RESULT                    
                                                                                
ABC                C : __ABC              V   F   T     OK                      
ABC                C : ABC                V   T   F     OK                      
ABC                C : ABC_               V   F   T     OK                      
ABC                C : ___ABC__           V   F   T     OK                      
ABC                C : (NULL STRING)      V   F   T     OK                      
ABC                C : ABCD               V   F   T     OK                      
___0X9             V : _0X9__             C   F   T     OK                      
0X9                V : _0X9__             C   F   T     OK                      
0X9__              V : _0X9__             C   F   T     OK                      
_0X9__             V : _0X9__             C   T   F     OK                      
__                 V : ____               V   F   T     OK                      
_                  V : (NULL STRING)      V   F   T     OK                      
18_CHARACTERS_LONG V : 18_CHARACTERS_LONG V   T   F     OK                      
18_CHARACTERS_LONG V : 18_CHARACTERS_LONK V   F   T     OK                      
!#$%&'()0=+*<>?    V : !#$%&'()0=+*<>?    V   T   F     OK                      
(NULL STRING)      V : (NULL STRING)      V   T   F     OK                      
UVWXYZ_            V : UVWXYZ__           V   F   T     OK                      
                                                                                
*** TEST PASSED ***                                                             
                                                                                
                  END TEST.                                                     
                                                                                
END PROGRAM 18                                                                  
                                                                                
Program interrupted at line 1940                                                
