Length of string

[amal.sultan.5855]

how to find length of a character string without using while loop or user defined function?

Have you tried Google... but these programming problems are pure tripe in the real world.

[Learner010]

without using while loop or user defined function?

with this line , your question becomes very easy.I'd say use library function.I think its str.length();

[rubberman]

There are C strings (char*) and C++ strings (std::string). Which are you using?

[Gonbe]

For C-Strings you could take a look at the cstring library, which contains a function named strlen. While you're not looking for a user-defined function, you could also define it yourself as it's quite straight forward. It'd look similar to this:

constexpr size_t strlen (const char text[])
{
    // Note: text[0] checks text[0] != '\0'
    return (text[0]) ? 1 + strlen(text + 1) : 0;
}

For string objects you would use the length member function.