ADAS Subroutine nsort

      SUBROUTINE NSORT(XA,IA,N)                                         
C
C-----------------------------------------------------------------------
C
C  ****************** FORTRAN77 SUBROUTINE: NSORT **********************
C
C PURPOSE:
C SUBROUTINE TO SORT AN ARRAY SO THAT XA IS INCREASING ORDER          
C                                                                    
C                                                                   
C INPUT                                                            
C     XA(I)=X-VALUES                                              
C     IA(I)=I-VALUES                                             
C     N=NUMBER OF VALUES                                        
C OUTPUT                                                       
C     XA(I)=SORTED X-VALUES                                   
C     IA(I)=SORTED I-VALUES                                  
C                                                           
C NOTES: THIS ROUTINE IS NOT YET PROPERLY ANNOTATED
C
C UNIX-IDL PORT:
C
C VERSION: 1.1                          DATE: 01-02-96
C MODIFIED: TIM HAMMOND (TESSELLA SUPPORT SERVICES PLC)
C               - PUT UNDER SCCS CONTROL
C
C-----------------------------------------------------------------------
      INTEGER             IA(*),       N
      REAL                XA(*)