Hello; I have this simple code: int a; cin >> a; cout << a; if I enter a char (r) instead of an int (23) I get a whole number : 3154592 I know that i'm entering a wrong variable type, but can any one explain what's going behind the scene?? thanks.

I know that Perl automatically converts non-numerical characters to zero when working with numbers...maybe this is doing similar?

something like cin >> a; if(cin.fail()) { cin.clear(1); cin.ignore(80); } Does some error checking. Once stream errors occur, you need to reset the fail bit before other operations can be done. The underlying cause is most likely the way the data types are represented at the machine level, but I'm not positive. You can reduce stream errors by using char types for numerical input, and then convert them using strtol, strtod, etc.

Or you could change a to a character array. Not a great example but it works: char a[5]; int num; bool usenum = false; cin >> a; if (a[0] >= '0' && a[0] <= '9') { usenum = true; for (int i = 0; i < strlen(a); i++) { num *= 10; num += a[i] - '0'; } } if (usenum == false) cout << a; else cout << num;

This may or may not help, but extractors, inserters, and other overloaded operators from the iostream lib are probably not returning the value of the correct type. It may be as simple as no implicit conversion to a char (in which case you would have to explicitly downcast it using a static cast (depending on the compiler you are using.)) It may also be a decimal representation of the address of a uninitialized char or void pointer to returned to cout (depending upon which overloaded function is called iac with how your overloaded left/right shift operators are defined.) You may also want to look at the behavior of the derived 'ostringstream' definition of class 'ios' in the iostream lib for your compiler. Eric