What is an Identifier and Keyword? Explain the rules for naming valid Identifiers in C with example.Write a program to convert a given string to lowercase without using any library functions.[5+5]

An identifier is a name given to various program elements such as variables, functions, arrays, structures, and user-defined types. Identifiers are used to uniquely identify a program element within its scope. Example: --- A keyword is a reserved word that has a predefined meaning in the C langua...