octave: X11 DISPLAY environment variable not set
octave: disabling GUI features
warning: implicit conversion from numeric to char
warning: called from
    reverseFile at line 13 column 13

Your reverse.txt:
efiL ocisoH fo yad enO
gnimmiwS
ocisoH rof dnalyensiD
xaler ot yad doog a s'tI
xoB daerB taC gnizamA ehT
ocisoH tuoba stcaF
!yaD yrotciV yppaH
emoh ta srebmucuc worg ylkciuq ot woH
skeehc yffulf s'ocisoH gnigassam rof tseb eht era seldnah elttil esehT

Your reverse.txt:
efiL ocisoH fo yad enO
gnimmiwS
ocisoH rof dnalyensiD
xaler ot yad doog a s'tI
xoB daerB taC gnizamA ehT
ocisoH tuoba stcaF
!yaD yrotciV yppaH
emoh ta srebmucuc worg ylkciuq ot woH
skeehc yffulf s'ocisoH gnigassam rof tseb eht era seldnah elttil esehT