Lesson 2 starting output
- 2. Remember these they work in our editor Operation Key Combo Cut ctrl + x Copy ctrl + c Paste ctrl + v Save ctrl + s Undo ctrl + z
- 3. //first program – this is a comment #include <iostream> int main() { return 0; } basic application review
- 4. Some languages provide keywords to perform specific tasks for, class, int C++ uses functions and classes for just about everything A library called The Standard Library comes with your tools And the tools know where to find it Libraries
- 5. #include<iostream> this includes a library that allows us to use the We use libraries all the time in programming You will be using many at times Operands insertion >> and extraction << operators cout << and cin >> std:: cout << //allows data to be read from the stream std::cin >> //allows data to be sent to the stream endl is the end line command (like hitting the enter key) We can use using namespace std; at the top of a program This allows us not to type std:: before every cout << or cin >> statement.
- 6. cout << Output stream – anything following can be output to the screen Text is enclosed in “ “ and is considered a literal. Numbers are considered literals and print as they are. Expressions are evaluated and the result printed. cout << “hello”; displays the word hello to the screen. cout << 2; displays the number 2 cout << “2”; will work too. cout << 2 + 2; displays 4 cout << “2 + 2”; displays 2 + 2 cout << endl; drops to next line
- 7. cout << “” is an escape sequence. The compiler is looking for another character to do something at that point. Sometimes you need to print a “” or a “ but they are part of the syntax so this allows you a way. Example cout << “hellonworld”; displays: hello world The n is for new line Others include Escape sequence character represented a Alarm (Beep, Bell) b Backspace f Formfeed n Newline (Line Feed) r Carriage Return t Horizontal Tab v Vertical Tab Backslash ' Single quotation mark " Double quotation mark ? Question mark
- 8. Issues endl needs to be it’s own statement ex. Can’t be cout << “Hello” cout << endl; has to be cout << “Hello”; cout <<endl; or cout << “Hello”; cout << endl; Can be cascaded on the same cout without the semi colon - Best Way! ex. cout << “Hello” << endl; //makes it easier to follow as a programmer
- 9. C++ runs in sequence so we need the libraries set as below – Top – Down Design #include <iostream> using namespace std; Notice the formatting – white space / indenting and next lines // this will run just fine but would be a nightmare to code and read #include <iostream> int main(){return 0;} //this is what we need #include <iostream> int main() { return 0; } Don’t ask for the impossible 3/0 or “hello” + 2
- 10. Outputting to the screen Remember – if you don’t tell the compiler what you want specifically you wont get it cout << “ ******” ; cout << “ ** “ ; Will display ****** ** Not ****** ** cout << “******” << endl; //added the end line – also cascaded cout <<“ ** “; Will display ****** ** You can cascade many output statements as long as you remember the extraction operators << in between cout << “ *******” << endl << “ ** “ << endl; // will work – notice new extraction operator and no ; until the end Also remember your screen resolution my be different than the information you are compiling Might not fir the way you want.
- 11. *********** *** * * * * * * *** * * * * * * ***** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *********** *** * *