C++ Programming Code Examples

/* SNAKE WAR - I */ #include <graphics.h> #include <iostream.h> #include <conio.h> #include <dos.h> #include <stdlib.h> #include <stdio.h> //#pragma warn -wrch #define MAX 50 #define UP_ARROW 72 #define DOWN_ARROW 80 #define LEFT_ARROW 75 #define RIGHT_ARROW 77 #define WinMinX 40 #define WinMaxX 600 #define WinMinY 40 #define WinMaxY 440 enum Direction {Forward,Backward,Upward,Downward}; struct Coord { int x , y; }; class Snake; class Point { int x , y , color ; public: Point ( ) { set (); } void set(); void draw( ); int getx() { return x; } int gety() { return y; } friend int point_vanished ( Point &p , Snake &s ); }; class Snake { Coord *_Snake; int _CurSize, _color,_MaxSize, _Points; char _player; Direction _Direction; public: Snake ( int size = 20, int color = RED , char player = 'M' ) { _Snake = new Coord [ size ]; _CurSize = 3; if ( player == 'C' ) { _Snake [0].x = WinMaxX - 10; _Direction = Backward; } else { _Snake [0].x = WinMinX + 10; _Direction = Forward; } //_Snake [0].x = WinMinX + 10; _Snake [0].y = WinMinY + 10; _color = color; _MaxSize = size; _player = player; _Points = 0; } void set( int size = 20, int color = RED , char player = 'M' ) { delete _Snake; _Snake = new Coord [ size ]; _CurSize = 3; if ( player == 'C' ) { _Direction = Backward; _Snake [0].x = WinMaxX - 10; } else { _Snake [0].x = WinMinX + 10; _Direction = Forward; } _Snake [0].x = WinMinX + 10; //_Snake [0].y = WinMinY + 10; _color = color; _MaxSize = size; _player = player; _Points = 0; } void change_direction ( Direction d); void increment (); void inc_disp (); void shift_all (); void display ( int color = BLACK ); void com_play ( Point p1 ); friend int point_vanished ( Point &p , Snake &s ); }; //>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> void Sound ( int s ); void Message_Display ( char msg[30] , char color ); void show_Header(); void signature(); int menu (); void drawMenu ( int selected , int defCol , int selCol ); void show_About(); void show_HowTOPlay(); void show_New(); void Play(); //>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> int main() { int g = DETECT , d; initgraph ( &g , &d , "d:\tc\bgi" ); int selected_option; Start: selected_option = menu(); switch ( selected_option ) { case 1: Play(); goto Start; case 2: show_HowTOPlay(); goto Start; case 3: show_New(); goto Start; case 4: show_About(); goto Start; case 5: return 1; } return 1; } void Snake :: increment ( ) { //int i; shift_all(); if ( _Direction == Forward ) { if ( _Snake[0].x >= WinMaxX ) { _Snake[0].x = WinMinX ; } else _Snake[0].x = _Snake[0].x + 10; } else if ( _Direction == Backward ) { if ( _Snake[0].x <= WinMinX ) { _Snake[0].x = WinMaxX ; } else _Snake[0].x = _Snake[0].x - 10; } else if ( _Direction == Upward ) { if ( _Snake[0].y <= WinMinY ) { _Snake[0].y = WinMaxY ; } else _Snake[0].y = _Snake[0].y - 10; } else if ( _Direction == Downward ) { if ( _Snake[0].y >= WinMaxY ) { _Snake[0].y = WinMinY ; } else _Snake[0].y = _Snake[0].y + 10; } } void Snake :: shift_all () { int i; for ( i = _CurSize -1 ; i > 0; i-- ) { _Snake[i].x = _Snake[i-1].x; _Snake[i].y = _Snake[i-1].y; } } void Snake :: inc_disp () { display ( BLACK ); increment(); display ( _color ); } void Snake :: display ( int color) { setfillstyle ( 1, color ); if ( color == 0 ) { setcolor ( 0 ); bar ( _Snake[_CurSize - 1].x - 5 , _Snake[_CurSize - 1].y - 5 , _Snake[_CurSize - 1].x + 5 , _Snake[_CurSize - 1].y + 5 ); rectangle ( _Snake[_CurSize - 1].x - 5 , _Snake[_CurSize - 1].y - 5 ,_Snake[_CurSize - 1].x + 5 , _Snake[_CurSize - 1].y + 5 ); //return ; } else { setcolor ( WHITE ); for ( int i = 0; i< _CurSize; i++ ) { bar ( _Snake[i].x - 5 , _Snake[i].y - 5 , _Snake[i].x + 5 , _Snake[i].y + 5 ); rectangle ( _Snake[i].x - 5 , _Snake[i].y - 5 , _Snake[i].x + 5 , _Snake[i].y + 5 ); } /* //int i = 0; bar ( _Snake[i].x - 5 , _Snake[i].y - 5 , _Snake[i].x + 5 , _Snake[i].y+ 5 ); rectangle ( _Snake[i].x - 5 , _Snake[i].y - 5 , _Snake[i].x + 5 ,_Snake[i].y ); */ setfillstyle ( 1 , 0 ); fillellipse ( _Snake[0].x , _Snake[0].y , 2 , 2); char msg[50]; setcolor ( WHITE ); if ( _player == 'C' ) { bar ( 250 , 12 , 630 , WinMinY - 10 ); sprintf ( msg , "Com Snake at :- ( %d , %d ) Score:- %d", _Snake[0].x, _Snake[0].y , _Points ); outtextxy ( 250 , 12 , msg ); } else { bar ( 250 , 1 , 630 , WinMinY - 10 ); sprintf ( msg , "Ur Snake at :- ( %d , %d ) Score:- %d", _Snake[0].x, _Snake[0].y , _Points ); outtextxy ( 250 , 1 , msg ); } } } void Snake :: change_direction ( Direction d) { if ( ( _Direction == Forward ) && ( d == Backward ) ) { Sound ( -1 ); } else if ( ( _Direction == Backward ) && ( d == Forward ) ) { Sound ( -1 ); } else if ( ( _Direction == Upward ) && ( d == Downward ) ) { Sound ( -1 ); } else if ( ( _Direction == Downward ) && ( d == Upward ) ) { Sound ( -1 ); } else { _Direction = d; Sound ( 1 ); } } void Point :: draw ( ) { char msg[30]; setfillstyle ( 1 , color ); setcolor ( YELLOW ); bar ( x - 4 , y - 4 , x + 4 , y + 4 ); rectangle ( x - 4 , y - 4 , x + 4 , y + 4 ); setfillstyle ( 1 , 0 ); fillellipse ( x , y , 2 , 2 ); bar ( 1 , 1 , 300 , WinMinY - 10 ); sprintf ( msg , "Point at :- ( %d , %d )", x , y ); outtextxy ( 40 , 1 , msg ); } void Point :: set ( ) { color = random ( 15 ) + 1; x = random ( ( ( WinMaxX - WinMinX ) / 10 ) ) ; y = random ( ( ( WinMaxY - WinMinY ) / 10 ) ) ; x = ( x * 10 ) + WinMinX; y = ( y * 10 ) + WinMinY; draw ( ); } int point_vanished ( Point &p , Snake &s ) { if ( ( s._Snake[0].x == p.x ) && ( s._Snake[0].y == p.y ) ) { s._CurSize++; if ( s._CurSize == s._MaxSize ) { return 2; } s.increment (); s.display ( RED ); Sound ( 2 ); delay ( 100 ); s._Points = s._Points + 20 ; p.set(); return 1; } else { return -1; } } void Sound ( int s ) { if ( s == -1 ) { sound ( 150 ); delay ( 30 ); sound ( 250 ); delay ( 30 ); nosound (); } else if ( s == 1 ) { sound ( 450 ); delay ( 20 ); nosound (); } else if ( s == 2 ) { sound ( 650 ); delay ( 20 ); nosound (); } } void Snake :: com_play ( Point p1 ) { if ( p1.getx() < _Snake[0].x ) { if ( _Direction == Forward ) _Direction = p1.gety() < _Snake[0].y ? Upward : Downward; else _Direction = Backward; } else if ( p1.getx() > _Snake[0].x ) { if ( _Direction == Backward ) _Direction = p1.gety() < _Snake[0].y ? Upward : Downward; else _Direction = Forward; } else { if ( p1.gety() < _Snake[0].y ) { _Direction = Upward; } else if ( p1.gety() > _Snake[0].y ) { _Direction = Downward; } } } void Message_Display ( char msg[30] , char color ) { settextstyle ( 1 , 0 , 5 ); setcolor ( 8 ); outtextxy ( 195 , 205 , msg); settextstyle ( 1 , 0 , 5 ); setcolor ( color ); outtextxy ( 200 , 200 , msg); delay ( 1000 ); } int menu () { int ch; int selected = 1; int TotalOptions = 5; cleardevice(); setbkcolor ( BLUE ); show_Header(); signature(); drawMenu ( selected , RED , GREEN ); do { ch = getch(); if ( ch == DOWN_ARROW ) { selected = selected >= TotalOptions ? 1 : selected + 1; drawMenu ( selected , RED , GREEN ); } else if ( ch == UP_ARROW ) { selected = selected < 2 ? TotalOptions : selected - 1; drawMenu ( selected , RED , GREEN ); } }while ( ch != ' ' ); return selected; } void drawMenu ( int selected , int defCol , int selCol ) { int x = 250; int y = 100; int width = 150; int height = 30; int i; int TotalOptions = 5; char menu_option[5][14]= { " PLAY ", " HOW TO PLAY ", " WHAT'S NEW ", " ABOUT ME ", " EXIT " }; setcolor ( WHITE ); for ( i = 1; i <= TotalOptions; i++ ) { if ( i == selected ) setfillstyle ( 1 , selCol ); else setfillstyle ( 1 , defCol ); bar ( x , y , x + width , y + height ); rectangle ( x , y , x + width , y + height ); outtextxy ( x + 20 , y + 10 , menu_option[i - 1] ); y = y + height + 30; } } void show_About() { cleardevice(); setbkcolor ( BLACK ); show_Header(); setcolor ( WHITE ); settextstyle ( 0 , 0 , 0 ); signature(); getch(); } void show_HowTOPlay() { cleardevice(); setbkcolor ( BLACK ); show_Header(); settextstyle ( 0 , 0 , 0 ); setcolor ( WHITE ); outtextxy ( 20 , 100 , "Objective:" ); outtextxy ( 20 , 150 , "Playing:" ); outtextxy ( 20 , 220 , "Tip:" ); setcolor ( LIGHTGREEN ); outtextxy ( 120 , 120 , "To collect 50 boxes before the computer Snake." ); outtextxy ( 120 , 170 , "1. Use arrow keys to control your Snake." ); outtextxy ( 120 , 180 , "2. To collect the box just come near to the BOX." ); outtextxy ( 120 , 190 , "3. Press <ESC> to QUIT any time." ); outtextxy ( 120 , 240 , "1. Use shortcuts to collect the BOX. [ Computer Snake never " ); outtextxy ( 120 , 250 , " uses shortcut]" ); outtextxy ( 120 , 260 , "2. Computer Snake can't Hurt you, so enjoy moving around." ); signature(); getch(); } void signature() { outtextxy ( 350 , 400 , "WWW " ); } void show_Header() { setcolor ( RED ); settextstyle ( 1 , 0 , 4 ); outtextxy ( 193 , 27 , " SNAKE WAR - I " ); setcolor ( YELLOW ); outtextxy ( 195 , 25 , " SNAKE WAR - I " ); } void show_New() { cleardevice(); setbkcolor ( BLACK ); show_Header(); settextstyle ( 0 , 0 , 0 ); setcolor ( WHITE ); outtextxy ( 20 , 100 , "What's new" ); outtextxy ( 20 , 150 , "What's next" ); outtextxy ( 20 , 260 , "When to expect next version" ); outtextxy ( 20 , 320 , "Comments, Bugs and Suggestions" ); setcolor ( LIGHTGREEN ); outtextxy ( 70 , 120 , "Nothing, cos it's the first version. :-)" ); outtextxy ( 70 , 170 , "In next version of this Game:- " ); outtextxy ( 90 , 180 , " > One or more player will be able to play." outtextxy ( 90 , 190 , " > You'll be able to select Zero or more computer players." ); outtextxy ( 90 , 200 , " > You'll be able to PAUSE the Game any time." ); outtextxy ( 90 , 210 , " > You'll be able to select the color of each snake." ); outtextxy ( 90 , 220 , " > Keys will be customizable." ); outtextxy ( 90 , 230 , " > Snakes will be able to Hurt each other." ); outtextxy ( 70 , 280 , "Don't worry, i'll mail the code of next version too. [ Very Soon ]" ); outtextxy ( 70 , 340 , "For any suggestion or comment or Bug report feel free to mail me." ); outtextxy ( 70 , 350 , "There may be Bugs too in this game, so please let me know them." ); signature(); getch(); } void Play() { Snake s1 ( MAX , GREEN , 'M' ); Snake s2 ( MAX , MAGENTA , 'C' ); char ch , KeyPressed = 0; cleardevice(); randomize (); rectangle ( WinMinX - 7, WinMinY - 7, WinMaxX + 7 , WinMaxY + 7 ); Point p1; setbkcolor ( BLUE ); s1.inc_disp(); s2.inc_disp(); setcolor ( YELLOW ); outtextxy ( 10 , 450 , "> Collect 50 Boxes to WIN. > Use shortcuts to WIN."); setcolor ( CYAN ); outtextxy ( 10 , 460 , "> Use <ESC> to QUIT anytime. > LEFT , RIGHT , UP , DOWN Arrow Keys to Play. "); getch(); KeyPressed = 1; ch = 'R'; while ( 1 ) { while ( !kbhit() ) { s1.inc_disp(); if ( point_vanished ( p1 , s1 ) == 2 ) { Message_Display ( "YOU WIN " , GREEN ); ch=0x1b; getch(); break; } s2.com_play ( p1 ); s2.inc_disp(); if ( point_vanished ( p1 , s2 ) == 2 ) { Message_Display ( "YOU LOSE " , GREEN ); ch=0x1b; getch(); break; } delay ( 100 ); if ( KeyPressed == 1 )KeyPressed = 0; } if ( ch == 0x1b ) break; ch = getch(); if ( KeyPressed == 1 ) { KeyPressed = 0; continue; } if ( ch == 0x1b ) break; else if ( ch == 0 ) { ch = getch (); if ( ch == UP_ARROW ) { s1.change_direction ( Upward ); KeyPressed = 1; } else if ( ch == DOWN_ARROW ) { s1.change_direction ( Downward ); KeyPressed = 1; } else if ( ch == LEFT_ARROW ) { s1.change_direction ( Backward ); KeyPressed = 1; } else if ( ch == RIGHT_ARROW ) { s1.change_direction ( Forward ); KeyPressed = 1; } } } }

/* The bar() function is used to draw a bar ( of bar graph) which is a 2-dimensional figure. It is filled rectangular figure. The function takes four arguments that are the coordinates of (X, Y) coordinates of the top-left corner of the bar {left and top } and (X, Y) coordinates of the bottom-right corner of the bar {right and bottom}. */ /* draw a filled-in, rectangular, two-dimensional bar by bar() function code example. */ #include <graphics.h> // driver code int main() { // gm is Graphics mode which is // a computer display mode that // generates image using pixels. // DETECT is a macro defined in // "graphics.h" header file int gd = DETECT, gm; // initgraph initializes the // graphics system by loading a // graphics driver from disk initgraph(&gd, &gm, ""); // location of sides int left, top, right, bottom; // left, top, right, bottom denotes // location of rectangular bar bar(left = 150, top = 150, right = 190, bottom = 350); bar(left = 220, top = 250, right = 260, bottom = 350); bar(left = 290, top = 200, right = 330, bottom = 350); // y axis line line(100, 50, 100, 350); // x axis line line(100, 350, 400, 350); getch(); // closegraph function closes the // graphics mode and deallocates // all memory allocated by // graphics system . closegraph(); return 0; }

/* multi-dimensional arrays in C++ language */ /* taking input for two dimensional array */ #include <iostream> using namespace std; int main() { int numbers[2][3]; cout << "Enter 6 numbers: " << endl; // Storing user input in the array for (int i = 0; i < 2; ++i) { for (int j = 0; j < 3; ++j) { cin >> numbers[i][j]; } } cout << "The numbers are: " << endl; // Printing array elements for (int i = 0; i < 2; ++i) { for (int j = 0; j < 3; ++j) { cout << "numbers[" << i << "][" << j << "]: " << numbers[i][j] << endl; } } return 0; }

/* hold the program's execution for given number of milliseconds by delay() function code example. */ #include<iostream.h> #include<dos.h> //for delay() #include<conio.h> //for getch() int main() { clrscr(); int n; cout<<"Enter the delay (in seconds) you want to make after giving input."<<endl; cin>>n; delay(n*1000); cout<<"This has been printed after "<< n <<" seconds delay"; getch(); return 0; }

/* While Loop Statement in C++ language */ // program to find the sum of positive numbers // if the user enters a negative number, the loop ends // the negative number entered is not added to the sum #include <iostream> using namespace std; int main() { int number; int sum = 0; // take input from the user cout << "Enter a number: "; cin >> number; while (number >= 0) { // add all positive numbers sum += number; // take input again if the number is positive cout << "Enter a number: "; cin >> number; } // display the sum cout << "\nThe sum is " << sum << endl; return 0; }

/* sound() function produces the sound of a specified frequency. */ int k; //loop to increment the value of a till 100. for ( k = 1 ; a <= 100 ; a = k++ ) { //calling the function for producing //the sound of value a. sound(a); //delay the sound 10 miliseconds. delay(10); } // function to stop the system sound. nosound(); return 0;

/* The header file graphics.h contains setfillstyle() function which sets the current fill pattern and fill color. floodfill() function is used to fill an enclosed area. Current fill pattern and fill color is used to fill the area. */ #include <graphics.h> // driver code int main() { // gm is Graphics mode which is // a computer display mode that // generates image using pixels. // DETECT is a macro defined in // "graphics.h" header file int gd = DETECT, gm; // initgraph initializes the // graphics system by loading // a graphics driver from disk initgraph(&gd, &gm, " "); // center and radius of circle int x_circle = 250; int y_circle = 250; int radius=100; // setting border color int border_color = WHITE; // set color and pattern setfillstyle(HATCH_FILL,RED); // x and y is a position and // radius is for radius of circle circle(x_circle,y_circle,radius); // fill the color at location // (x, y) with in border color floodfill(x_circle,y_circle,border_color); getch(); // closegraph function closes the // graphics mode and deallocates // all memory allocated by // graphics system closegraph(); return 0; }

/* outtextxy() function displays the text or string at a specified point (x, y) on the screen. */ // C++ Implementation for outtextxy() #include <graphics.h> int main() { textcolor(RED); cleardevice(); setcolor(RED); outtextxy(150,205,"Enter the Username:"); outtextxy(150,245,"Enter the Password:"); outtextxy(150,355,"Thank you"); outtextxy(150,445,"nice job"); outtextxy(50,105,"good day"); outtextxy(50,145,"pan"); outtextxy(50,255,"go"); outtextxy(50,245,"nice day"); return 0; }

/* cleardevice erases (that is, fills with the current background color) the entire graphics screen and moves the CP (current position) to home (0,0). */ #include <graphics.h> int main() { clrscr(); cleardevice(); int flag=44; setbkcolor(3); draw(); char m[20]; char a[20][20]={"2xqwer4fgi","trewq9y3ry","yuip7qtgfm","jpiuy9bph6","klkjh6decc", "etlhjklo2k","lasdfapl4z","efghjv5qy","mmjnhlmt8t","134rfvup5n"}; randomize(); int r=random(10)+1; settextstyle(SCRIPT_FONT, HORIZ_DIR, 5); outtextxy(190,0,"level 8"); line(190,60, 300, 60); settextstyle(SCRIPT_FONT, HORIZ_DIR, 3); outtextxy(0,100,"\nplease this is the last time!!!"); cout<<endl<<endl<<endl<<endl<<endl<<endl<<endl<<endl<<endl<<"\t"; for(int i=0;a[r][i]!='\0';i++) { cout<<a[r][i]; td(); cout<<" "; td(); } clrscr(); cleardevice(); return 0; }

/* deallocate storage space by delete operator */ #include <iostream> using namespace std; int main () { // declaration of variables int *ptr1, *ptr2, sum; // allocated memory space using new operator ptr1 = new int; ptr2 = new int; cout << " Enter first number: "; cin >> *ptr1; cout << " Enter second number: "; cin >> *ptr2; sum = *ptr1 + *ptr2; cout << " Sum of pointer variables = " << sum; // delete pointer variables delete ptr1; delete ptr2; return 0; }

/* initgraph initializes the graphics system by loading a graphics driver from disk (or validating a registered driver), and putting the system into graphics mode. To start the graphics system, first call the initgraph function. initgraph loads the graphics driver and puts the system into graphics mode. You can tell initgraph to use a particular graphics driver and mode, or to autodetect the attached video adapter at run time and pick the corresponding driver. */ int DGraphics::Init( int gmode ) { int gdriver = VGA, errorcode; gdriver=installuserdriver("SVGA256",NULL); initgraph(&gdriver, &gmode, ""); if ( (errorcode = graphresult()) != grOk ) { cout << "Error: Graphics - %s\n" << grapherrormsg(errorcode); return FALSE; } ActiveMode=gmode; return TRUE; }

/* the switch statement helps in testing the equality of a variable against a set of values */ #include <iostream> using namespace std; int main () { // local variable declaration: char grade = 'D'; switch(grade) { case 'A' : cout << "Excellent!" << endl; break; case 'B' : case 'C' : cout << "Well done" << endl; break; case 'D' : cout << "You passed" << endl; break; case 'F' : cout << "Better try again" << endl; break; default : cout << "Invalid grade" << endl; } cout << "Your grade is " << grade << endl; return 0; }

/* change the background to the color specified by color in graphics mode. */ /* Program to make digital clock in C++ graphics */ #include<graphics> #include<conio.h> #include<time.h> int main() { initwindow(700,500,"CLOCK",300,100);//displays graphics window char t[15],date[10]; while(1) { setbkcolor(5);//set background color _strtime(t);//pick system time and saves in char array setcolor(11);//color of time settextstyle(4, HORIZ_DIR, 8);//font of time outtextxy(100, 100, t);//prints time delay(1000); } getch(); closegraph(); }

/* continue statement skips the execution of further statements in the block and continues with the next iteration. */ // program to calculate positive numbers till 50 only // if the user enters a negative number, // that number is skipped from the calculation // negative number -> loop terminate // numbers above 50 -> skip iteration #include <iostream> using namespace std; int main() { int sum = 0; int number = 0; while (number >= 0) { // add all positive numbers sum += number; // take input from the user cout << "Enter a number: "; cin >> number; // continue condition if (number > 50) { cout << "The number is greater than 50 and won't be calculated." << endl; number = 0; // the value of number is made 0 again continue; } } // display the sum cout << "The sum is " << sum << endl; return 0; }

/* The sprintf() function in C++ is used to write a formatted string to character string buffer. It is defined in the cstdio header file. */ /* Write formatted data to string by sprintf() function code example */ #include <cstdio> #include <iostream> using namespace std; int main() { char buffer[100]; int count; char name[] = "Max"; int age = 23; // write combination of strings and variables to buffer variable // store the number of characters written in count count = sprintf(buffer, "Hi, I am %s and I am %d years old", name, age); // print the string buffer cout << buffer << endl; // print the number of characters written cout << "Number of characters written = " << count; return 0; }

/* simple code example by main() function in C++ */ #include <iostream> using namespace std; int main() { int day = 4; switch (day) { case 1: cout << "Monday"; break; case 2: cout << "Tuesday"; break; case 3: cout << "Wednesday"; break; case 4: cout << "Thursday"; break; case 5: cout << "Friday"; break; case 6: cout << "Saturday"; break; case 7: cout << "Sunday"; break; } return 0; }

/* you can simply silent the system by nosound() function code example. */ #include <stdio.h> //to use 'sound()', 'delay()' functions #include <dos.h> int main() { //calling the function for producing //the sound of frequency 400. sound(400); //function to delay the sound for //half of second. delay(500); //calling the function to stop the //system sound. nosound(); return 0; }

/* break statement with while loop code example */ // program to find the sum of positive numbers // if the user enters a negative numbers, break ends the loop // the negative number entered is not added to sum #include <iostream> using namespace std; int main() { int number; int sum = 0; while (true) { // take input from the user cout << "Enter a number: "; cin >> number; // break condition if (number < 0) { break; } // add all positive numbers sum += number; } // display the sum cout << "The sum is " << sum << endl; return 0; }

/* #define directive in C++ language */ #include <bits/stdc++.h> using namespace std; void func1(); void func2(); #pragma startup func1 #pragma exit func2 void func1() { cout << "Inside func1()\n"; } void func2() { cout << "Inside func2()\n"; } int main() { void func1(); void func2(); cout << "Inside main()\n"; return 0; }

/* C++ allows us to allocate the memory of a variable or an array in run time. This is known as dynamic memory allocation. The new operator denotes a request for memory allocation on the Free Store. If sufficient memory is available, new operator initializes the memory and returns the address of the newly allocated and initialized memory to the pointer variable. */ /* Allocate storage space by operator new */ // C++ program code example to illustrate dynamic allocation and deallocation of memory using new and delete #include <iostream> using namespace std; int main () { // Pointer initialization to null int* p = NULL; // Request memory for the variable // using new operator p = new(nothrow) int; if (!p) cout << "allocation of memory failed\n"; else { // Store value at allocated address *p = 29; cout << "Value of p: " << *p << endl; } // Request block of memory // using new operator float *r = new float(75.25); cout << "Value of r: " << *r << endl; // Request block of memory of size n int n = 5; int *q = new(nothrow) int[n]; if (!q) cout << "allocation of memory failed\n"; else { for (int i = 0; i < n; i++) q[i] = i+1; cout << "Value store in block of memory: "; for (int i = 0; i < n; i++) cout << q[i] << " "; } // freed the allocated memory delete p; delete r; // freed the block of allocated memory delete[] q; return 0; }

/* For Loop Statement in C++ Language */ // C++ program to find the sum of first n natural numbers // positive integers such as 1,2,3,...n are known as natural numbers #include <iostream> using namespace std; int main() { int num, sum; sum = 0; cout << "Enter a positive integer: "; cin >> num; for (int i = 1; i <= num; ++i) { sum += i; } cout << "Sum = " << sum << endl; return 0; }

/* Structure is a collection of variables of different data types under a single name. It is similar to a class in that, both holds a collecion of data of different data types. */ #include <iostream> using namespace std; struct Person { char name[50]; int age; float salary; }; int main() { Person p1; cout << "Enter Full name: "; cin.get(p1.name, 50); cout << "Enter age: "; cin >> p1.age; cout << "Enter salary: "; cin >> p1.salary; cout << "\nDisplaying Information." << endl; cout << "Name: " << p1.name << endl; cout <<"Age: " << p1.age << endl; cout << "Salary: " << p1.salary; return 0; }

/* setcolor() function change the current drawing color in graphic mode. */ #include<stdio.h> #include<conio.h> #include<graphics.h> void main() { int gd=DETECT,gm; initgraph(&gd,&gm," "); setbkcolor(5);//set background color setcolor(11);//color of time settextstyle(4, HORIZ_DIR, 8);//font of time setcolor(GREEN); circle(320,240,100); setcolor(RED); outtextxy(320,80."It is circle"); getch(); closegraph(); }

/* a friend function can access the private and protected data of a class. */ // C++ program to demonstrate the working of friend function #include <iostream> using namespace std; class Distance { private: int meter; // friend function friend int addFive(Distance); public: Distance() : meter(0) {} }; // friend function definition int addFive(Distance d) { //accessing private members from the friend function d.meter += 5; return d.meter; } int main() { Distance D; cout << "Distance: " << addFive(D); return 0; }

/* kbhit() function is not defined as part of the ANSI C/C++ standard. It is generally used by Borland's family of compilers. It returns a non-zero integer if a key is in the keyboard buffer. It will not wait for a key to be pressed. */ // C++ program code example to fetch key pressed using kbhit() #include <conio.h> #include <iostream> int main() { char ch; while (1) { if (kbhit) { // Stores the pressed key in ch ch = getch(); // Terminates the loop // when escape is pressed if (int(ch) == 27) break; cout << "Key pressed= " << ch; } } return 0; }

/* Enum is a user defined data type where we specify a set of values for a variable and the variable can only take one out of a small set of possible values. We use enum keyword to define a Enumeration. */ #include <bits/stdc++.h> using namespace std; int main() { // Defining enum Gender enum Gender { Male, Female }; // Creating Gender type variable Gender gender = Male; switch (gender) { case Male: cout << "Gender is Male"; break; case Female: cout << "Gender is Female"; break; default: cout << "Value can be Male or Female"; } return 0; }

/* If Else Statement in C++ Language */ #include <iostream> using namespace std; int main () { // local variable declaration: int a = 100; // check the boolean condition if( a < 20 ) { // if condition is true then print the following cout << "a is less than 20;" << endl; } else { // if condition is false then print the following cout << "a is not less than 20;" << endl; } cout << "value of a is : " << a << endl; return 0; }

/* settextstyle() function sets the current text font, direction and character size. All calls to outtext() and outtextxy() are affected by the new settings. */ int main() { int gm, gd; gd = VGA; gm = VGAHI; initgraph(&gd, &gm, ""); settextstyle(SANS_SERIF_FONT, HORIZ_DIR, 4); outtextxy(32, 8, "SANS_SERIF_FONT"); settextstyle(DEFAULT_FONT, HORIZ_DIR, 4); outtextxy(32, 58, "DEFAULT_FONT"); settextstyle(GOTHIC_FONT, HORIZ_DIR, 4); outtextxy(32, 108, "GOTHIC_FONT"); settextstyle(SCRIPT_FONT, HORIZ_DIR, 4); outtextxy(32, 158, "SCRIPT_FONT"); getch(); closegraph(); }

/* wait for any character input from keyboard by getch() function code example. The getch() function is very useful if you want to read a character input from the keyboard. */ // C code to illustrate working of // getch() to accept hidden inputs #include<iostream.h> #include<conio.h> void main() { int a=10, b=20; int sum=0; clrscr(); sum=a+b; cout<<"Sum: "<<sum; getch(); // use getch() befor end of main() }

/* function rectangle() draws a rectangle in graphic mode. */ int main() { // location of left, top, right, bottom int left = 150, top = 150; int right = 450, bottom = 450; // initgraph initializes the graphics system // by loading a graphics driver from disk initgraph(&gd, &gm, ""); // rectangle function rectangle(left, top, right, bottom); left = 200, = 250; right = 150, = 300; rectangle(left, top, right, bottom); left = 100, = 200; right = 450, = 100; rectangle(left, top, right, bottom); getch(); return 0; }

/* using #include directive in C language */ #include <stdio.h> int main() { /* * C standard library printf function * defined in the stdio.h header file */ printf("I love you Clementine"); printf("I love you so much"); printf("HappyCodings"); return 0; }

/* fillellipse() function draws an ellipse and fill it with current drawing color and pattern. */ /* draws an ellipse and fill it by fillellipse() function code example */ #include <graphics.h> // driver code int main() { // gm is Graphics mode which is // a computer display mode that // generates image using pixels. // DETECT is a macro defined in // "graphics.h" header file int gd = DETECT, gm; // initgraph initializes the // graphics system by loading a // graphics driver from disk initgraph(&gd, &gm, ""); // fillellipse fuction fillellipse(200, 200, 50, 90); getch(); // closegraph function closes the // graphics mode and deallocates // all memory allocated by // graphics system . closegraph(); return 0; }