编写//凯撒密码的模拟程序 //1：用于凯撒密码的加密 //2：用于已知密钥的解密 //3：用于未知密钥的解密 //0：表示退出该程序-Preparation// Caesar password simulation program// 1: for Caesar encryption// 2: for the decryption key is known// 3: unknown key for decryption// 0: exit of the express proc