As of now, your line variable is of type char. This means that it holds a single character. If you want to store a string, you can either use a fixed size array of characters (a c-style string) or a string object. In c++ string objects should be preferred as they offer a wide array of advantages over c-style strings including greater security and superior ease of use.
If you wanted to get the length of a user inputed string object for example, you could write something like this
#include <iostream>
#include <string>
// if you don’t want to use std:: put using namespace std; after the includes
int main(){
std::string str;
int strLength
std::cout << “Enter a Single Word: “;
std::cin >> str;
strLength = str.lenght();
std::cout << “The length of the word is “ << strLength << std::endl;
return 0;
}
If you want to get a full line of text instead, you would replace
std::cout << “Enter a Single Word: “;
std::cin >> str;
With
std::cout << “Enter a Line of text: “;
std::getline(cin, str);
You could also use a c-style string and strlen() however, it is far more difficult to do this securely and it will make it easier to cause issues by doing something like writing a string longer than the size of the fixed size array used which can cause issues as the extra data can be written to areas it should not be written to, so if your just starting out you should probably use string objects.
If you want more information on std::string, go to
https://en.cppreference.com/w/cpp/string/basic_string
On why strlen is returning 40. The way strlen() works is it takes a variable called a pointer that points to the start of an array of characters and goes through an array of characters starting at the pointer and looks for a special character called the null character ‘\0’ and returns the number of characters in the array before this null character. This can cause problems if a c-style string does not end in a null character.
In the case of the code you provided, string2 contains all 40 characters inside of the “” plus the null character at the end, so when strlen() is called using string2, it counts the 40 characters before the null character.
In the case of string1, when it is created, it is created with the size equal to the value contained in the uninitialized variable line, which in this case appears to be 0. This causes string1 to be created with a size of 0 (according to the language standard this is undefined behavior but it may still “work” in some cases). Because string2 is later created in a position directly after string1 in memory, the pointer to the start of string1 created when string1 is passed into strlen points to the start of string2 causing strlen to effectively measure the length of string2 when called on string1.
Finally, as a tip. Try to avoid placing variables in the global scope (outside of functions or other encapsulating entities like classes). These global variables are at risk of being unintentionally altered by functions in ways that might cause problems in your code. It is generally better to place these variables in main and pass them to the functions you want to use them in. If you want to have the function affect these variables, you can pass them into the function as references. To do this you would place an & behind the type of the parameter of the function the variable will be passed in as, like this.
void function(std::string &str);
//… some other code
//… somewhere in main or another function
function(alteredString);
// some other code …
