#!/bin/bash

files=("file1.txt" "file2.txt" "file3.txt")

echo ${files[2]} ${files[1]} ${files[0]}

# file3.txt file2.txt file1.txt

echo ${files[*]} # file1.txt file2.txt file3.txt

echo ${#files[@]} # 3

files[0]="nofile"

echo ${files[*]} # nofile file2.txt file3.txt