In a program using string functions like `strlen` and `strcpy`, you need to include the `<string.h>` header file.
The `<string.h>` header file is a standard C library header file that contains various functions and macros for manipulating strings. It provides function prototypes and declarations for functions like `strlen` (used to determine the length of a string) and `strcpy` (used to copy one string to another).
By including the `<string.h>` header file at the beginning of your program, you make these string functions available for use in your code. The functions and macros defined in `<string.h>` help simplify string manipulation and enable you to perform operations on strings more easily.
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