C++ Basics
CSE250
Derived from slides provided by Dr.
Hung Ngo
Logistics
• Office hours
– Tuesday 2-3
– Thursday 2-3
– Wednesday 4-5?
• Course repository link on Piazza
C++
• There will be a lot of information in this
lecture
• You should practice writing C++
How and Where to compile
• Command line
• IDE of choice
• Up to you, but your submissions must compile
and run on the CSE servers
The procedural parts of c++
C-style strings
Pointers and references
GETTING STARTED IN C++
Agenda
• The main body and cout
• Fundamental data types
• Declarations and definitions
• Control structures
• //References, pass-by-value vs pass-by-reference
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CSE 250, SUNY Buffalo, © Hung Q. Ngo
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C++ is an OO extension of C
C++ has both procedural and object-oriented features
We will use C++ as a procedural language with objects
THE MAIN BODY AND COUT
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CSE 250, SUNY Buffalo, © Hung Q. Ngo
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Every
C++
program
must
have
a
main()
// hw.cpp
Somewhat similar to Java’s import
#include <iostream>
int main() {
std::cout << "Hello world" << std::endl;
return 0;
}
Similar to Java’s namespace
• iostream is a C++ abstraction to perform input/output
operations on media using “streams”
Important in system programming, not in CSE 250.
– Media as character streams: keyboard, files, console, network sockets
– cout is an output stream object associated with the console
– “writing to cout” using << will print to the console
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CSE 250, SUNY Buffalo, © Hung Q. Ngo
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cout is pretty easy to use
#include <iostream>
using namespace std; // questionable
int main()
string
string
string
{
my_name
= "David Blaine";
my_text_editor = "Emacs";
my_home_os
= "Windows";
cout <<
<<
<<
<<
<<
return 0;
"My name is " << my_name << endl
"I was able to install and test g++ and "
"the text editor " << my_text_editor << '\n'
"in my home computer/laptop, which runs "
my_home_os << endl;
}
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CSE 250, SUNY Buffalo, © Hung Q. Ngo
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They are what you expect them to be, similar to those in Java
FUNDAMENTAL DATA TYPES
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CSE 250, SUNY Buffalo, © Hung Q. Ngo
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The fundamental data types
Boolean, characters, integers, floats, and void
• bool : true or false
• char : a character
• int : an integer
• float : a floating-point real number
•
wchar_t, char16_t, char32_t, short, long, signed,
unsigned, float, double, …
• And cout will output a variable with the
appropriate format for the above types
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CSE 250, SUNY Buffalo, © Hung Q. Ngo
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Cout is easy to use on basic types
#include <iostream>
using namespace std; // bad practice!
int main() {
string name
char c
int i
bool smart
double avg
=
=
=
=
=
cout << "I am
<< "smart
<< "c = "
<< "i = "
<< "avg =
return 0;
"David Blaine";
'H';
12345;
true;
3.5;
" << name << endl
= " << smart << endl
<< c << endl
<< i << endl
" << avg << endl;
}
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CSE 250, SUNY Buffalo, © Hung Q. Ngo
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Every name must be declared before used
There must always be at most one definition for each named entity
There can be many declarations
Many declarations are also definitions
DECLARATIONS AND DEFINITIONS
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CSE 250, SUNY Buffalo, © Hung Q. Ngo
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Declarations
// variable declarations
string name; char c; int i;
bool smart; double avg;
// a type declaration (the type is a struct)
struct Date;
// a const bool declaration
const bool i_am_smart = true;
// a function declaration
int foo(int);
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CSE 250, SUNY Buffalo, © Hung Q. Ngo
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Definitions
// definition of function foo()
int foo(int x) {
return x*x;
}
// definition of struct Date
struct Date {
int d;
int m;
int y;
};
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CSE 250, SUNY Buffalo, © Hung Q. Ngo
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Many declarations are also definitions
// these declarations are *also* definitions
string name;
char c;
int i;
bool smart;
double avg;
// these declarations are *not* definitions
int foo(int);
struct Date;
extern int age;
typedef vector<int> Int_Vector;
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Again
• Every name (identifier) must be declared before use
• A name can be declared multiples times
– Helps with separate compilation.
– Defined in one file, declared and used in others
– More about this in a couple of lectures
• There is ≤ 1 definition per name
• Some declarations are also definitions
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