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## Command Line Arguments

- The sample program (`caesar.cpp`) is used to encrypt a file - that is, scrambles it so that it is unreadable except to those who know the decryption method and the secret keyword.
- This program uses a method familiar to Julius Caesar.
  - The person performing any encryption chooses an encryption key (a number between 1 and 25).
  - The key indicates the shift to be used in encrypting each letter. (For example, if the key is 3, we replace A with D, B with E, etc.).

    > Plain Text |  | `M` | `e` | `e` | `t` |  | `m` | `e` |  | `a` | `t` | `. . .`
    > Encrypted Text |  | `P` | `h` | `h` | `w` |  | `p` | `h` |  | `d` | `w` | `. . .`

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