Write a program with three functions: upper, lower, and flip.The upper function should accept a C-string as an argument. Itshould step through all the characters in the string, convertingeach to uppercase. The lower function, too, should accept a pointerto a C-string as an argument. It should step through all thecharacters in the string, converting each to lowercase. Like upperand lower, flip should also accept a C-string. As it steps throughthe string, it should test each character to determine whether itis upper- or lowercase. If a character is uppercase, it should beconverted to lowercase. If a character is lowercase, it should
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