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In cryptography, a substitution cipher is a method of encoding by which units of plaintext are replaced with cipher text, according to a regular system; the "units" may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. There are a number of different types of substitution cipher. One type of substitution cipher i simple substitution cipher which operates on single letters. bstitution of single letters separately-simple substitution-can be demonstrated by writi out the alphabet in some order to represent the substitution. This is termed a substitution alphabet. Keys for the simple substitution cipher usually consist of 26 letters. + program to encrypt or cipher a text file ( eFile.txt ). The text files does contain small letters, capital letter, numbers, spaces, and symbols. If the file does not exist, the program should terminate with a file not found error message displayed on the screen. The output ( encrypted text) will be displayed on the screen as 50 character per line. For this program, the following keys are used: Plaintext alphabet: ABCDEFGHIJKLMNOPORSTUVWXYZ Cipher text alphabet : EMNVDLWAUCPOKXQBIZJRYTGSHF 0123456789 Numbers Cipher numbers: 9876543210 Special symbols : Cipher special symbols : 0][@?>=<: space replacer symbols>