What is the purpose of the strlen function in C++?

In C++, the purpose of the strlen function is to calculate the length of a null-terminated string, which is the number of characters in the string excluding the null character. The function prototype is as follows:

size_t strlen(const char* str);

In this case, str is a pointer to a string that ends with null. The function will iterate through the characters starting from the specified string until it encounters a null character, then it will return the number of characters (excluding the null character) as the length of the string.