Notes

Outline

COM1100 Fundamentals of Computer Science Winter 2000

Announcement Please visit course web site periodically.    www.ccs.neu.edu/course/com1100    COM1100_Winter_Announcement.html Packages are now available at Gnomon Copy. Package 1 – Patterns Package 2 – Recitation 1 ~ 5 Package 3 – Lab 1 ~5

Reading material this week Textbook Chapter 1 : Introduction Chapter 2 : Fundamental Data Types Package 1 – Patterns Name Use Pattern - Part 1 - Variables and Objects Read-Process-Write Pattern Reading Data Pattern

Today’s lecture C++ Origins Line by line analysis of our first C++ program Output statement : cout Input statement : cin

The Origins of C++ In 1970’s, Dennis Ritchie at AT&T Bell Labs created the C programming language under UNIX Many ideas came from a programming language BCPL(Basic Combined Programming Language, or B) C++ was developed in 1985 at Bell Labs by Bjarne Stroustrup

The Origins of C++  -- cont. Bjarne added features for data abstraction and object-oriented programming. Instead of naming it as programming language D, the Bell Labs group in a humorous vein named it C++ (suggests an enhancement version of C) Structural programming, not object-oriented programming in COM1100.

ANSI Standard C++ Because there are many versions of C++, we need to have a standard. ANSI (American National Standards Institute)

The process of programming Writing source code (source program: test.cpp) Text editor (Notepad, VC++ IDE) Compiling (object program : test.obj) Compiler to translate source code to machine language Linking (Executable program : test.exe) Linker to combine object files and library files so that they can be executed as a unit Loading and Executing Loader to load .exe file into memory and be executed

First C++ program 1 #include <iostream> 2 using namespace std; 3 int main() 4 { 5   cout << "Hello, World\n"; 6 7 return 0; 8 }

Line by line analysis #include <iostream> –  It is a preprocessor command. Preprocessor command begins with a pound sign(#) and perform some action before the compiler translate the source program into machine language.  –  Tells the compiler to read the file iostream.h . This file contains definition for stream input/output package. –  In our example, cout performs output onto the screen and therefore requires the service provided in iostream.h

#include <iostream> -- The iostream is referred as header file because it is placed at the top, or head, of a C++ program using #include command –  Preprocessor commands do not end with a semicolon #include <iostream>   #include <string>

using namespace std; –Tell the compiler that all names that are used in the program belong to the “standard name space” – A namespace is a mechanism for expressing logical grouping. – That is, if some declarations logically belong together according to some criteria, they can be put in a common namespace to express that fact. – You will always use the standard name space in this course.

int main() Begins the definition of a function called main. A C++ program begins execution in the function main. – A function is a collection of programming instructions that carry out a particular task. – Every C++ program must have a main function – Most C++ programs contain other functions besides main

{ … } Curly braces marks the beginning and the ending of the block of statements belonging to the function main. – The instructions or statements in the body of main function – that is, the statements inside the curly braces { } – are executed one by one. – Each statement in a C++ program ends in a semicolon.

cout << "Hello, World\n"; Invokes library function cout to display output on the screen (standard output device). –The quoted text string is called a constant string and is displayed as-is. The double quotes are used to delimit the beginning and ending of the constant string and are not considered part of the string. – The << operator denotes the “put to” or “send to” command.

cout << "Hello, World\n"; – The two character \ and n, when used together ( \n ), is called a newline escape sequence. They tell cout to send instruction to the display device to move to a new line. – In C++, the backslash ( \ ) character provides an “escape” from the normal interpretation of the character following it by altering the meaning of the next character.

return 0; The return statement denoted the end of the main function. When the main function ends, the program terminates. The zero value is a signal that the program ran successfully.

First C++ program 1 #include <iostream> 2 using namespace std; 3 int main() 4 { 5   cout << "Hello, World\n"; 6 7 return 0; 8 }

C++ Syntax header files using namespace std; int main() { statements; return 0; }

Compiler differences Textbook, chapter1, page 26 “Advanced Topic 1.1” The header file of older compilers have an extension .h #include <iostream.h> But new compilers do not need .h extension    #include <iostream>    using namespace std;

Output statement -- Syntax Purpose:    Print the value of one or more expressions Syntax: cout << expression1 << expression2 << … << expressionN; Expressions should be separated by <<

Output statement -- Examples cout << “Hello, World \n” ;    Hello, World cout << “Hello, World ”  << endl;    Hello, World cout << “Hi, ”  << “Elice” << endl;    Hi, Elice cout << “Hi, \n”  << “Elice” << endl;    Hi,    Elice

Output statement -- Examples cout << 7 + 8 ;    15 cout << “7 + 8 = “ << 7 + 8 ;    7 + 8 = 15 cout << “\” Hi ! \” ” << endl;    “Hi !” cout << “ Hello \\ World ! “ << endl;    Hello \ World !

Input statement -- Syntax Purpose:    Read the value of one or more variables from the input Syntax: cin >> variable1 >> variable2 >>…>> variableN; Variables should be separated by >>

Input statement -- Examples int first, second, last;    cin >> first;    cin >> second;    cin >> last; It is also possible to read more than one values from the keyboard    int first, second, last;    cin >> first >> second >> last;

Input statement -- Examples int first, second, last;      cin >> first >> second >> last; When type in these three numbers from keyboard, they should be separated by white space (blank spaces, tabs, or newlines) 12  6  15 12       6       15

Summary of today’s lecture C++ was developed in 1985 at Bell Labs by Bjarne Stroustrup C++ is a better C. header files using namespace std; int main() { statements; return 0; } cout << expression1 << expression2 << … << expressionN; cin >> variable1 >> variable2 >>…>> variableN;

Tomorrow’s lecture Variable declare and use Programming style Safe I /O operations Assignment statements Arithmetic operations