What is ios::in|ios::out?

Question

I was reading some project code and I found this,here MembersOfLibrary() is a constructor of class MenberOfLibrary

class MembersOfLibrary {
  public:
    MembersOfLibrary();
    ~MembersOfLibrary() {}
    void addMember();
    void removeMember();
    unsigned int searchMember(unsigned int MembershipNo);
    void searchMember(unsigned char * name);
    void displayMember();

  private:
    Members    libMembers;

};

MembersOfLibrary::MembersOfLibrary() {

    fstream memberData;
    memberData.open("member.txt", ios::in|ios::out);
    if(!memberData) {
    cout<<"\nNot able to create a file. MAJOR OS ERROR!! \n";
    }
    memberData.close();
}

What is ios::in|ios::out?

Answer 1

• ios::in allows input (read operations) from a stream.
• ios::out allows output (write operations) to a stream.
• | (bitwise OR operator) is used to combine the two ios flags,
  meaning that passing ios::in | ios::out to the constructor
  of std::fstream enables both input and output for the stream.

---

Important things to note:

• std::ifstream automatically has the ios::in flag set.
• std::ofstream automatically has the ios::out flag set.
• std::fstream has neither ios::in or ios::out automatically
  set. That's why they're explicitly set in your example code.

Answer 2

 memberData.open("member.txt", ios::in|ios::out);

ios::in is used when you want to read from a file

ios::out is used when you want to write to a file

ios::in|ios::out means ios::in or ios::out, that is whichever is required is used

Here's a useful link

http://www.cplusplus.com/doc/tutorial/files/