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Introduction to C/C++. Hello World. #include using namespace std; void main( int argc, char **argv ) { cout
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Introduction to C/C++
Hello World
#include <iostream>
using namespace std;void main( int argc, char **argv ){
cout << “Hello World!” << endl;cin.get( );return 0;
}
What is the purpose of the program?
#include <iostream>
using namespace std;void main( int argc, char **argv ){
cout << “Hello World!” << endl;cin.get( );return 0;
}
The purpose of the program is ……
Hello World#include <iostream> // header file <- comment
using namespace std; //namespace
/* <- comment Entry function. There is only one main in the entire project.*/int main( int argc, char **argv ) // parameter list{
//output to console windowcout << “Hello World!” << endl;
cin.get( ); //read a keyreturn 0; //return
}
#include <iostream>
• Take everything in the header and copy it into the program.
#include <iostream>using namespace std;void main( int argc, char **argv ) {
cout << “Hello World!” << endl;cin.get( );return 0;
}
using namespace std;
• Inform the compiler to use a group of functions which are defined in the standard library, i.e. std.
#include <iostream>using namespace std;void main( int argc, char **argv ) {
cout << “Hello World!” << endl;cin.get( );return 0;
}
int main( int argc, char **argv )
• int : the return data type• main: the function name• ( …… ) : parameter list
• int argc : argc is a parameter. – Its data type is int
• char **argv : argv is a parameter. – Its datatype is char**
#include <iostream>using namespace std;void main( int argc, char **argv ) {
cout << “Hello World!” << endl;cin.get( );return 0;
}
{ …. }
• A structure block
e.g.,
{int a; a = 1 + 2;
}
#include <iostream>using namespace std;void main( int argc, char **argv ) {
cout << “Hello World!” << endl;cin.get( );return 0;
}
cout << “Hello World!” << endl;• cout : a functionl output on the console window• << : an operator• “Hello World!” : a string• endl : a function; output a newline• ; : end of a statement.
#include <iostream>using namespace std;void main( int argc, char **argv ) {
cout << “Hello World!” << endl;cin.get( );return 0;
}
Primitive Data Type• int : integer ( 4 bytes )• float : single precision floating point number ( 4 bytes )• double : double precision floating point number ( 8 bytes )• char : character (1 byte)• unsigned int : unsigned integer ( 4 bytes )
• int * : a pointer to integer ( 4 bytes )• char * : a pointer to integer ( 4 bytes ) • char ** : a pointer to an integer pointer ( 4
bytes ) A size of a pointer is 4 bytes.
Example OneFixing the bugs
//Find the bugs and fix them.include <iostream
Using namespace standard;
void main( int argc, char ** argv ){
int a = 2 + 3;cout << a << endlreturn ;
• An empty page
Example OneFixing the bugs
#include <iostream>
using namespace std; // case sensitive
int main( int argc, char ** argv ){
int a = 2 + 3;cout << a << endl;return 0;
}
Array
An array is a container object that store a fixed number of values of a single type.e.g.int a[16]; // a[0], a[1], …, a[15]double b[32]; // b[0], b[1], …, b[31]const int numOfElements = 1000;char messageStr[numOfElements ];
……
Example Two• Write a program to read a string and then output the characters of
the string one by one at each new line.#include <iostream>#include <string>using namespace std;void main ( int argc, char **argv ) {
string message;cin >> message;int n = message.size( );for ( int i = 0; i < n; ++i ) {
cout << message[i] << endl;}cin.get( );
} // build and run the program. What do you see? How to stop it?
#include <iostream>#include <string>using namespace std;void main ( int argc, char **argv ) {
string message;cin >> message;int n = message.size( );for ( int i = 0; i < n; ++i ) {
cout << message[i] << endl;}system(“pause”);
}
Stop the program
Example Three
• Write a program to enter the information of students.
• The information of a student includes:– name– score
Show the average score of the students.Show the score range, i.e., [min, max].
Example Three
• Write a program to enter the information of students.
• The information of a student includes:– name– score
What is(are) the data structure(s)?
Example Three
• Write a program to enter the information of students.
• The information of a student includes:– name– score
What is(are) the data structure(s)?name?score?
Example Three
• Write a program to enter the information of students. • The information of a student includes:
– name– score
What is(are) the data structure(s)?name?score?Number of students?
Example Three• Write a program to enter the information of students. • The information of a student includes:
– name– Score
What is(are) the data structure(s)?name?score?Number of students?
int n; // n is the number of studentsstring name[n];int score[n];But ERROR!
Example Three• Write a program to enter the information of students. • The information of a student includes:
– name– Score
What is(are) the data structure(s)?name?score?Number of students?
int n; // n is the number of studentsstring name[n];int score[n];
But ERROR! n is not a constant.
Example Three• Write a program to enter the information of students. • The information of a student includes:
– name– Score
What is(are) the data structure(s)?name?score?Number of students?
#define max_students 1024int n; // n is the number of studentsstring name[max_students];int score[max_students];
Example ThreeUsing C++
class Student_Record {public:
string name;int score; Student_Record ( ) { // constructor
name.clear( );score = 0;
}};
Example ThreeUsing C++
• Write a program to enter the information of students. • The information of a student includes:
– name– score
Show the average score of the students.Show the score range, i.e., [min, max].
• Algorithm?
Example ThreeUsing C++
• Algorithm
Show a message “Please enter #students”
For each studentEnter name and score
End for
Compute avarage scoreCompute score rangeShow the average scoreShow the score range
Example ThreeUsing C++
• Algorithm
Show a message “Please enter #students”
For each studentEnter name and score
End for
Compute avarage scoreCompute score rangeShow the average scoreShow the score range
Management system
Example Three: Using C++#define MAX_STUDENTS 1024
class ManagementSystem {
protected:
int mCurNumOfStudents; //number of students
Student_Record sr[MAX_STUDENTS];
float mAverageScore;
int mMinScore, mMaxScore;
public:
};
Example Three: Using C++#define MAX_STUDENTS 1024
class ManagementSystem {
public:
ManagementSystem( ) { mCurNumOfStudents = 0; }
void inputRecords( );
void computeAverage( );
void computeSoreRange( );
float getAverageScore( ) const;
void getScoreRange( int &min, int &max ) const;
};
Example Threevoid inputRecords( )
void ManagementSystem:: inputRecords( )
{
int n;
cout << “Number of students:”;
cin >> n;
if ( n <= 0 ) return;
else mCurNumOfStudents = n;
for ( int i = 0; i < n; ++i ) {
cout << “student:” << i << “\t” << “name:”;
cin >> sr[ i ].name;
cout << “score:”;
cin >> sr[ i ].score;
}
}
Example Threevoid computeAverage( )
void ManagementSystem:: computeAverage( )
{
int totalScore = 0;
for ( int i = 0; i < mCurNumOfStudents ; ++i ) {
totalScore += sr[ i ].score;
}
mAverageScore = totalScore / mCurNumOfStudents ;
}
Example Threevoid computeAverage( )
void ManagementSystem:: computeAverage( )
{
int totalScore = 0;
for ( int i = 0; i < mCurNumOfStudents ; ++i ) {
totalScore += sr[ i ].score;
}
// BUG?
mAverageScore = totalScore / mCurNumOfStudents ;
}
Example Threevoid computeAverage( )
void ManagementSystem:: computeAverage( )
{
int totalScore = 0;
for ( int i = 0; i < n; ++i ) {
totalScore += sr[ i ].score;
}
// mCurNumOfStudents = 0? Division by zero!!!
mAverageScore = totalScore / mCurNumOfStudents;
}
Example Threevoid computeAverage( )
void ManagementSystem:: computeAverage( )
{
if ( mCurNumOfStudents = 0 ) {
mAverageScore = 0;
return;
}
int totalScore = 0;
for ( int i = 0; i < mCurNumOfStudents ; ++i ) {
totalScore += sr[ i ].score;
}
// There is still a BUG!!!!!!!mAverageScore = totalScore / mCurNumOfStudents ;
}
Example Threevoid computeAverage( )
void ManagementSystem:: computeAverage( )
{
if (mCurNumOfStudents = 0 ) {
mAverageScore = 0;
return;
}
int totalScore = 0;
for ( int i = 0; i < mCurNumOfStudents ; ++i ) {
totalScore += sr[ i ].score;
}
// integer divisionmAverageScore = totalScore / mCurNumOfStudents ;
}
Example Threevoid computeAverage( )
void ManagementSystem:: computeAverage( )
{
if (mCurNumOfStudents = 0 ) {
mAverageScore = 0;
return;
}
int totalScore = 0;
for ( int i = 0; i < mCurNumOfStudents ; ++i ) {
totalScore += sr[ i ].score;
}
mAverageScore = totalScore / (float) mCurNumOfStudents ;
}
Example Threevoid computeAverage( )
void ManagementSystem:: computeAverage( )
{
if (mCurNumOfStudents = 0 ) {
mAverageScore = 0;
return;
}
int totalScore = 0;
for ( int i = 0; i < mCurNumOfStudents ; ++i ) {
totalScore += sr[ i ].score;
}
// There is still a BUG!!!!!!!!!!!!!!!
mAverageScore = totalScore / (float) mCurNumOfStudents ;
}
Example Threevoid computeAverage( )
void ManagementSystem:: computeAverage( )
{
if (mCurNumOfStudents = 0 ) {
mAverageScore = 0;
return;
}
int totalScore = 0;
for ( int i = 0; i < mCurNumOfStudents ; ++i ) {
totalScore += sr[ i ].score;
}
// Truncation error! The value mAverageScore may not be correct.
// e.g., 973/10 = 97.3, but it cannot be represented as binary representation
mAverageScore = totalScore / (float) mCurNumOfStudents ;
}
• Please refer to the tutorial.
