SUBROUTINE PCHAR(BUF,IDX,CHAR)
      INTEGER BUF(1),IDX,CHAR,SHIFT(4),MASK(4)  
      INTEGER IPOS  
      DATA  MASK/Z00FFFFFF,ZFF00FFFF,ZFFFF00FF,ZFFFFFF00/   
      DATA SHIFT/       24,       16,        8,        0/   
      I=ISHFT(IDX+3,-2) 
      IPOS=IAND(IDX-1,3)+1  
      BUF(I)=IAND(BUF(I),MASK(IPOS))+ISHFT(IAND(CHAR,255),SHIFT(IPOS))  
      RETURN
      END