C Collection of code snippets by Arne Vajhøj 
C (from articles on eksperten.dk / vajhoej.dk written sometime between 2004 and now) 
      PROGRAM BKSP
      INTEGER*4 IV
      CHARACTER*80 SV
      OPEN(UNIT=1,FILE='demo.txt',STATUS='OLD')
100   READ(UNIT=1,FMT=1000,END=500) SV
      IX=80
200   IF(SV(IX:IX).EQ.' ') THEN
        IX=IX-1
        GOTO 200
      ENDIF
      DO 300 I=1,IX
        IF(INDEX('0123456789',SV(I:I)).LE.0) GOTO 400
300   CONTINUE
      BACKSPACE(UNIT=1)
      READ(UNIT=1,FMT=1100,END=500) IV
      WRITE(*,*) 'IV=',IV      
      GOTO 100
400   WRITE(*,*) 'SV=',SV(1:IX)
      GOTO 100
500   CLOSE(UNIT=1)
1000  FORMAT(A)
1100  FORMAT(I8)
      END