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D. Mirkovic, C++ Programming, Spring 2005
Lecture 1: C++ Basics
Dragan Mirkovic
Department of Computer Science
University of Houston
Announcements
• Today:
– C++ Basics
– Ch 1. In Irvine.
– Introducing C++
• Basic terminology
• Standardization of C++
• C/C++ differences
D. Mirkovic, C++ Programming, Spring 2005
Introduction
- C++ is one of the most popular programming languages today
- Industrial-strength language
- Incorporates the efficiency of C with OO features
- Well-suited for development of large complex software systems and
libraries
- Strongly typed language
- Compiler performs strict type checking on variables and expressions
- Object-oriented (OO) approach:
- Focus on objects that make up an application problem
- Program structure: relationship between objects
- Process-oriented approach:
- Program is organized as a hierarchy of tasks (procedures)
- Procedural programming languages (C, Fortran, Pascal)
History of C++
- C was developed at Bell Labs around1969-1973 for implementation of the UNIX operating system, by Dennis Ritchie.
- 90% of UNIX was then written in C.
- 1989 - ANSI Standard for C
- C++ was written by Bjarne Sroustrup at Bell Labs during 1983-
- C++ is an extension of C. Prior to 1983, Bjarne Stroustrup added features to C and formed what he called "C with Classes".
- He had combined the use of classes and object-oriented features with the power and efficiency of C. The term C++ was first used in 1983.
D. Mirkovic, C++ Programming, Spring 2005
Inheritance
• Different objects can have some common attributes
and operations
• In some cases it is useful to define a base class
which contains the common characteristics
• Corresponds to “Is a” relationship in Entity-
relationship data model
• Example:
Vehicle
Car Truck Airplane
Base class
Derived classes
Polymorphism
• A single name can denote objects of different types
• The actual type of the object doesn’t have to be
known at compile time
• Most programming languages do not support
polymorphism
• Unions in C allow for a specific form of polymorphism
• In C++ polymorphic objects must be instances of
classes related by inheritance
• Example: calcSpeed() function for
Vehicle–Car–Truck–Airplane family
- Dynamic binding vs. static binding
D. Mirkovic, C++ Programming, Spring 2005
Structure of a C++ program
• Example:
// my first program in C++
#include <iostream.h>
int main () { cout << "Hello World!"; return 0; }
• Example :
_/ Equivalent program in C /_
#include <stdio.h>
int main () { printf(“Hello, World\n”); return 0; }
•Structure
–Comments (// line comment /* block comment */ )
–Preprocessor directives (#)
–the main function declaration.
–standard output steam cout , equivalent to stdout
Variables, data types, constants.
• Variable = a portion of memory to store a determined
value.
- Each variable needs an identifier that distinguishes it from the others a = 5; b = 2; a = a + 1; result = a - b;
• Identifier = a sequence of one or more letters, digits
or underline symbols ( _ ).
- The length of an identifier is not limited
- Variable identifiers should always begin with a letter or an underline character ( _ )
- they cannot match any key word
D. Mirkovic, C++ Programming, Spring 2005
Declaration of variables
- In order to use a variable in C++, we must first declare it
- The syntax: int a; float mynumber;
- Initialization of variables:
type identifier =
initial_value ;
Or
type identifier
(initial_value) ;
int a = 0; int a(0);
#include <iostream.h>
int main ()
// declaring variables:
int a, b;
int result;
// process:
a = 5; b = 2; a = a + 1;
result = a - b;
// print out the result:
cout << result;
// terminate the
program: return 0;
Scope of variables
• In C++ we can declare variables anywhere in the
source code (not in C)
•Global variables •Local variables •External variables
D. Mirkovic, C++ Programming, Spring 2005
Constants
• Literals:
- Integer, floats, characters and strings
- Examples:
- Integer: 75 // decimal 0113 // octal 0x4b // hexadecimal
- Floating point numbers: 3.14159 // 3. 6.02e23 // 6.02 x 10 23
- Character and strings: 'p’ "Hello world"
- Defined constants #define PI 3. #define NEWLINE '\n‘ #define WIDTH 100
- Declared constants
- With the const prefix you can
declare constants with a specific
type exactly as you would do
with a variable:
const int width = 100;
const char tab = '\t';
Operators
- Assignment: =
- Arithmetic operators: +, -, *, /, %
- Compound arithmetic operators: +=, -=, *=, /=, %=, >>=, <<=, &=, ^=, |=
- Increment/Decrement operators: ++, --
- Relational operators: ==, !=, >, <, >=, <=
- According to the ANSI-C++ standard, the result is a bool value
( true or false )
- Different from C (int)
- Logic operators: !, &&, ||
- Conditional operator:?
- Bitwise Operators: &, |, ^, ~, <<, >>
- Explicit type casting Operators: (type) or type()
D. Mirkovic, C++ Programming, Spring 2005
Reference Parameters
- Passing arguments by reference in C++
void swap(int &x, int &y) { int tmp = x; x = y; y = tmp; } int A = 20, B = 10; swap(A, B); cout << A << ',' << B;
- Passing arguments by reference in C
void swap(int *x, int *y) { int tmp = *x; *x = *y; *y = tmp; } int A = 20, B = 10; swap(&A, &B); printf("%d, %d\n", A, B);
Stream I/O
- Stream Output
- The stream output operator (<<) appends an expression to the
output stream
- Examples: cout << 10; // prints number 10 on screen cout << "Hello"; // prints Hello on screen cout << x; // prints the content of x variable on screen cout << "Hello, I am " << age << " years old.";
- When writing an expression use () to force evaluation of the
expression before printing
cout << (10 + x);
- Use a newline character ‘\n’ to force line breaks cout << (10 + x) << ‘\n’;
- Use endl stream manipulator a newline and flush the output buffer cout << (10 + x) << ‘\n’;
D. Mirkovic, C++ Programming, Spring 2005
Stream I/O
- Stream Input
- The stream input operator
(>>) extracts data from an
input stream
- Examples: int n; cin >> n; //read from input stream
- By default operator skips
whitespace (tabs, spaces,
new lines)
int a, b; float r; char ch; cin >> a >> b >> r >> ch;
- cin.get() can be used for character input - Example:
#include <iostream.h>
char name[80], ch = '\0';
int i = 0;
cout << "Enter your name:“
while(1)
cin.get(ch);
if(ch=='\n') break;
name[i++] = ch;
name[i] = '\0';
Summary
• C++ is an industrial-strength language
– Incorporates the efficiency of C with OO features
– Well-suited for development of large complex
software systems and libraries
– Strongly typed language
– Basic terminology:
- Objects, Classes, Inheritance, Polymorphism
– Differences between C and C++
– Stream I/O
