This document introduces C++ strings and I/O streams. It shows how to compose an email address from a name and domain, append to strings, extract substrings, and modify strings. Functions are defined to output integers and strings to stdout. The document also demonstrates reading user input, including integers and strings, from stdin. Finally, it defines a struct with name and number fields, overloads insertion and extraction operators for the struct, and uses these operators to read and write structs to I/O streams.

2. ‫معرفی‬String
‫معرفی‬I/O Stream‫ها‬

3. 01. string compose(const string& name, const string& domain)
02. {
03. return name + '@' + domain;
04. }
05.
06. auto addr = compose("dmr","bell–labs.com");
01. void m2(string& s1, string& s2)
02. {
03. s1 = s1 + 'n'; // append newline
04. s2 += 'n'; // append newline
05. }

4. 01. string name = "Niels Stroustrup";
02.
03. void m3()
04. {
05. string s = name.substr(6,10); // s = "Stroustrup"
06. // name becomes "nicholas Stroustrup"
07. name.replace(0,5,"nicholas");
08. // name becomes "Nicholas Stroustrup"
09. name[0] = toupper(name[0]);
10. }

5. 01. string incantation;
02.
03. void respond(const string& answer)
04. {
05. if (answer == incantation) {
06. // perform magic
07. }
08. else if (answer == "yes") {
09. // ...
10. }
11. // ...
12. }

6. 01. void f()
02. {
03. cout << 10;
04. }
01. void g()
02. {
03. int i {10};
04. cout << i;
05. }

7. 01. void h(int i)
02. {
03. cout << "the value of i is ";
04. cout << i;
05. cout << 'n';
06. }
the value of i is 10
01. void h2(int i)
02. {
03. cout << "the value of i is " << i << 'n';
04. }

8. 01. void f()
02. {
03. int i;
04. cin >> i; // read an integer into i
05. double d;
06. // read a double-precision floating-point number into d
07. cin >> d;
08. }
01. void hello()
02. {
03. cout << "Please enter your namen";
04. string str;
05. cin >> str;
06. cout << "Hello, " << str << "!n";
07. }

9. 01. void hello_line()
02. {
03. cout << "Please enter your namen";
04. string str;
05. getline(cin,str);
06. cout << "Hello, " << str << "!n";
07. }

10. 01. struct Entry {
02. string name;
03. int number;
04. };
01. ostream& operator<<(ostream& os, const Entry& e)
02. {
03. return os << "{"" << e.name << "", " << e.number << "}";
04. }

11. 01. // read { "name" , number } pair. Note: formatted with { " " , and }
02. istream& operator>>(istream& is, Entry& e)
03. {
04. char c, c2;
05. if (is>>c && c=='{' && is>>c2 && c2=="") { // start with a { "
06. // the default value of a string is the empty string: ""
07. string name;
08. while (is.get(c) && c!='"') // anything before a " is part of the name
09. name+=c;
10. if (is>>c && c==',') {
11. int number = 0;
12. if (is>>number>>c && c=='}') { // read the number and a }
13. e = {name,number}; // assign to the entry
14. return is;
15. }
16. }
17. }
18. is.setf(ios_base::failbit); // register the failure in the stream
19. return is;
20. }

12. { "John Marwood Cleese" , 123456 }
{"Michael Edward Palin",987654}
01. for (Entry ee; cin>>ee; ) // read from cin into ee
02. cout << ee << 'n'; // write ee to cout
{"John Marwood Cleese", 123456}
{"Michael Edward Palin", 987654}