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CS253 Introduction

Bjarne Stroustrup presents C++ to the Founding Fathers

Origin

• 1979: Bjarne Stroustrup, at AT&T Bell Labs, began work on “C with classes”.
• 1983: “C with classes” was renamed as “C++”.
• 1998: C++ first standardized by ISO

Preferences

• Which is better, Java or C++?

Dialects

• In this class, we’re learning C++, not g++.
• g++ is a particular implementation of C++.
• There are other C++ compilers: clang, Microsoft Visual Studio, etc.
• Similarly, there are many dialects of English, Spanish, French, etc.

Standards

• So, what is C++, then?
• How do we tell what’s real C++ and what’s a dialect?
• Let’s try some simpler questions:
  • Who’s the best pop singer? Beyoncé
    • Says who? the BeyHive
  • When is the holiday Washington's Birthday? third Monday in February
    • Says who? U.S. Congress
  • Is Pluto a planet? no
    • Says who? International Astronomical Union
  • How long is a meter? 1/299792458 light-second
    • Says who? International Standards Organization

Standard C++

• C++ is defined by ISO, the International Organization for Standardization (?), and its national member organizations such as ANSI, the American National Standards Institute.
• There are several versions of the C++ standard: 1998, 2003, 2011, 2014, 2017.
• This class focuses on C++ 2014 (alias C++14).
• I’ll let you get away with anything that g++ permits, however.
  • g++ implements extensions to the C++ standards.
    • Handy, but dangerous. It’s easy to produce non-standard code.

Standard

An HP co-worker, Donn Terry, used to say “Standard is better than better”. This meant that doing something in the standard way is superior to doing it in a non-standard way, even if the non-standard way yields better results. True enough, as far as it goes.

I want you to learn standard C++. That way, your programs will work everywhere, on any standard-conforming compiler. If you use compiler extensions, non-standard features, then your program will work on that particular compiler, but perhaps not on others. Not so good.

C++ is C

When C++ was being developed, C compatibility was very important. It still is. There are zillions of C programs out there, and the creator of C++ wanted it to be very easy to take a C program and turn it into a C++ program.

Therefore, C++ is just about a superset of C. This means that almost all C programs are C++ programs.

Valid C & C++

This is a valid C program, and a valid C++ program:

#include <stdio.h>
int main() {
    printf("Hello from C!\n");
    return 0;
}

Hello from C!

#include <stdio.h>
int main() {
    printf("Hello from C++!\n");
    return 0;
}

Hello from C++!

printf() is as much a part of C++ as int and while.

C++, not C

This is a valid C program, but it is not a valid C++ program, because C++ took over class as a keyword:

int main() {
    int class=0;
    return class;
}

c.cc:2: error: expected primary-expression before 'int'

This is a rare exception.

Better C++

Sure, it’s better C++ style to do the first program like this:

#include <iostream>
using namespace std;
int main() {
    cout << "Hello, world!\n";
    return 0;
}

Hello, world!

However, that doesn’t change the fact that the first program is C++.

A Final Note

• Despite all that, I don’t let you use certain C facilities (printf(), malloc() etc.) in this class.
• I will force you to use the corresponding C++ facilities (cout, new).
• I feel no guilt about this.
• It’s like removing the training wheels from your kid’s bicycle.