C homework need help

The program has two functions: - Cipher - Creates an encoded message - The program will ask the user to enter a plain string and add a Key value to each ASCII code of each character in the string. The program will display the resulting coded string on the screen. - DeCipher - Decode an encoded message - The program will ask the user to enter a coded string and subtract a Key value from each ASCII code of each character in the string. The program will display the resulting original/plain string on the screen. Program user inputs: - Operation selections prompt that asks the user which operation to perform. User selects - 1 for encoding a message - 2 for decoding a message - 0 to exit the program - String ( String ) - String to be used in encoding or decoding messages. - Key value (Int) - Key values are used as the shift amount for coded messages. - For example, for a value of Key =1. for each character, ' a ' becomes ' b ', ' b ' becomes ' c ' and ' A ' becomes ' B ' and so on. Program outputs: - Result of the selected operation. - The output should be Clear and indicate what happened. Sampleprogram run: Please Select the operation to perform (1-Encode String, 2-Decode String, 0-Exit): 1 Enter the plain string to encode: Hello Enter Key Value: 1 The Encoded string is: Ifmmp. Please Select the operation to perform (1-Encode String, 2-Decode String, 0-Exit): 2 Enter the encoded string: Ifmmp Enter Key Value: 1 The Decoded string is: Hello Please Select the operation to perform (1-Encode String, 2-Decode String, 0-Exit) : 0 Goodbye