Question

I’m using the 2D character arrays for storing multiple strings. The code below works fine & outputs the proper strings.

    char str[3][4];

    std::cin >> str[0] >> str[1] >> str[2] >> str[3];

    std::cout << str[0] << '\n' << str[1] << '\n' << str[2] << '\n' << str[3];

but when I try this

    char str[3][3];

    std::cin >> str[0] >> str[1] >> str[2];

    std::cout << str[0] << '\n' << str[1] << '\n' << str[2];

Then, if I input

abc

xyz

pqr

I get the output

abcxyzpqr

xyzpqr

pqr

What might be the possible explanation?

Answer 1

It’s because you’re allocating 3 chars per string and they are of length 3 – so there’s no \0 at the end of the string. C++ strings should end with a \0 to mark the end. When 4 chars are allocated, C++ automatically pads each string with a \0. It’s safe to create arrays of at least n+1 chars when you need to store at most n chars in that.

It seems that the total 9 chars of str are contiguous, so the first string is of length 9. The cout statement goes to print from str[0][0], and as there’s no \0 at the end of str[0], it continues printing str[1] and str[2].