C++ Programming Code Examples

/* Telephone */ #include<stdio.h> #include<string.h> main() { FILE *t,*p; char another,choice; struct telephone { char name[30]; long int code; long int number; }; struct telephone data; char custname[30]; long int n; long int recsize; t=fopen("TELEPHONE.DAT","rb+"); if(t==NULL) { t=fopen("TELEPHONE.DAT","wb+"); if(t==NULL) { printf("The File can't open\n"); exit(); } } printf(" TELEPHONE DIRECTORY \n"); printf(" ************* \n"); recsize=sizeof(data); while(1) { printf("\n\n"); printf("1.Add Records\n"); printf("2.List Records\n"); printf("3.Modify Records\n"); printf("4.Finding Number\n"); printf("5.Finding Name\n"); printf("6.Delete Records\n"); printf("0.Exit\n"); printf("Your Choice:"); fflush(stdin); choice=getche(); switch(choice) { case '1': fseek(t,0,SEEK_END); another='y'; while(another=='y') { printf("\nEnter Customer name,Code number and Telephone number\n"); scanf("%s %ld %ld",data.name,&data.code,&data.number); fwrite(&data,recsize,1,t); printf("Add another data(y/n):"); fflush(stdin); another=getche(); printf("\n"); } break; case '2': rewind(t); printf("\n"); printf("---------------------------------------------\n"); printf("| CUSTOMER | CODE | TELEPHONE |\n"); printf("---------------------------------------------\n"); rewind(t); while(fread(&data,recsize,1,t)==1) printf("| %-18s %-2ld %12ld |\n\n",data.name,data.code,data.number); printf("--------------------------------------------\n"); getch(); printf("\n"); break; case '3': another='y'; while(another=='y') { printf("\nEnter name of customer to modify:"); scanf("%s",custname); rewind(t); while(fread(&data,recsize,1,t)==1) { if(strcmp(data.name,custname)==0) { printf("\nEnter new name,code and telephone number\n"); scanf("%s %ld &ld",data.name,&data.code,&data.number); fseek(t,-recsize,SEEK_CUR); fwrite(&data,recsize,1,t); break; } } printf("Modify another record(y/n):"); fflush(stdin); another=getche(); printf("\n"); } break; case '4': another='y'; while(another=='y') { printf("\nEnter name of customer:"); scanf("%s",custname); rewind(t); while(fread(&data,recsize,1,t)==1) { if(strcmp(data.name,custname)==0) { printf("Telephone Number=%ld %ld\n",data.code,data.number); getch(); } } printf("Find another number(y/n)? "); fflush(stdin); another=getche(); printf("\n"); } break; case '5': another='y'; while(another=='y') { printf("\nEnter number of customer:"); scanf("%ld",&n); rewind(t); while(fread(&data,recsize,1,t)==1) { if(data.number==n) { printf("The Name is %s\n",data.name); getch(); } } printf("Find another name(y/n)? "); fflush(stdin); another=getche(); printf("\n"); } break; case '6': another='y'; while(another=='y') { printf("\nEnter name of customer to delete:"); scanf("%s",custname); p=fopen("TEMP.DAT","wb"); rewind(t); while(fread(&data,recsize,1,t)==1) { if(strcmp(data.name,custname)!=0) fwrite(&data,recsize,1,p); } fclose(t); fclose(p); remove("TELEPHONE.DAT"); rename("TEMP.DAT","TELEPHONE.DAT"); t=fopen("TELEPHONE","rb+"); printf("Delete another record(y/n):"); fflush(stdin); another=getche(); } break; case '0': printf("\n"); fclose(t); exit(); } } }

/* write block of data by ostream::write function code example */ /* in order to perform a binary input/output operation using the read() and write() functions, C++ provides us a few file stream classes */ // Copy a file #include <fstream> // std::ifstream, std::ofstream int main () { std::ifstream infile ("test.txt",std::ifstream::binary); std::ofstream outfile ("new.txt",std::ofstream::binary); // get size of file infile.seekg (0,infile.end); long size = infile.tellg(); infile.seekg (0); // allocate memory for file content char* buffer = new char[size]; // read content of infile infile.read (buffer,size); // write to outfile outfile.write (buffer,size); // release dynamically-allocated memory delete[] buffer; outfile.close(); infile.close(); 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; }

/* The sizeof() is an operator in C and C++. It is an unary operator which assists a programmer in finding the size of the operand which is being used. */ #include <iostream> using namespace std; int main() { int arr[]={10,20,30,40,50}; std::cout << "Size of the array 'arr' is : "<<sizeof(arr) << std::endl; cout << "Size of char : " << sizeof(char) << endl; cout << "Size of int : " << sizeof(int) << endl; cout << "Size of short int : " << sizeof(short int) << endl; cout << "Size of long int : " << sizeof(long int) << endl; cout << "Size of float : " << sizeof(float) << endl; cout << "Size of double : " << sizeof(double) << endl; cout << "Size of wchar_t : " << sizeof(wchar_t) << endl; return 0; }

/* fseek() in C language, is use to move file pointer to a specific position. Offset and stream are the destination of pointer, is given in the function parameters. If successful, it returns zero. If it is not successful, it returns non-zero value. */ /* Reposition stream position indicator by fseek() function code example */ #include <cstdio> int main() { FILE* fp = fopen("example.txt","w+"); char ch; fputs("Erica 25 Berlin", fp); rewind(fp); printf("Name: "); while((ch=fgetc(fp))!=' ') putchar(ch); putchar('\n'); printf("Age: "); fseek(fp,10,SEEK_SET); while((ch=fgetc(fp))!=' ') putchar(ch); putchar('\n'); printf("City: "); fseek(fp,15,SEEK_SET); while((ch=fgetc(fp))!=EOF) putchar(ch); putchar('\n'); fclose(fp); 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; }

/* 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; }

/* compare two strings by strcmp() string function code example */ #include <cstring> #include <iostream> using namespace std; int main() { char str1[] = "HappyCodings"; char str2[] = "Happy"; // returns -1 because "HappyCodings" < "Happy" lexicographically int result = strcmp(str1, str2); cout << "Comparing " << str1 << " and " << str2 << ": " << result << endl; // returns 1 because "Happy" > "HappyCodings" lexicographically result = strcmp(str2, str1); cout << "Comparing " << str2 << " and " << str1 << ": " << result << endl; // returns 1 because "HappyCodings" = "HappyCodings" lexicographically result = strcmp(str1, str1); cout << "Comparing " << str1 << " and " << str1 << ": " << result; return 0; }

/* terminate the process normally, performing the regular cleanup for terminating programs by exit() function code example */ #include<iostream> using namespace std; int main() { int i; cout<<"Enter a non-zero value: "; //user input cin>>i; if(i) // checks whether the user input is non-zero or not { cout<<"Valid input.\n"; } else { cout<<"ERROR!"; //the program exists if the value is 0 exit(0); } cout<<"The input was : "<<i; }

/* The function read() in <iostream> header file extracts n characters from the stream and stores them in the array pointed to the stream. Unlike functions put() and get() it is usually used to handle the data in binary form. */ /* extracts n characters from the stream and stores them in the array pointed by s with read() function code example. */ #include <iostream> #include <fstream> int main () { std::ifstream is ("test.txt", std::ifstream::binary); if (is) { is.seekg (0, is.end); int length = is.tellg(); is.seekg (0, is.beg); char * buffer = new char [length]; std::cout << "Reading " << length << " characters... "; is.read (buffer,length); if (is) std::cout << "all characters read successfully."; else std::cout << "error: only " << is.gcount() << " could be read"; is.close(); delete[] buffer; } 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; }

/* nested loop statement in C++ language */ // C++ program that uses nested for loop to print a 2D matrix #include <bits/stdc++.h> using namespace std; #define ROW 3 #define COL 3 // Driver program int main() { int i, j; // Declare the matrix int matrix[ROW][COL] = { { 4, 8, 12 }, { 16, 20, 24 }, { 28, 32, 36 } }; cout << "Given matrix is \n"; // Print the matrix using nested loops for (i = 0; i < ROW; i++) { for (j = 0; j < COL; j++) cout << matrix[i][j]; cout << "\n"; } return 0; }

/* write a C program which demonstrate use of if-else-if ladder statement */ /* Program to Print Day Names using Else If Ladder in C++*/ #include <iostream> using namespace std; int main() { int day; cout << "Enter Day Number: "; cin >> day; cout << "Day is "; if (day == 1) cout << "Sunday" << endl; else if (day == 2) cout << "Monday" << endl; else if (day == 3) cout << "Tuesday" << endl; else if (day == 4) cout << "Wednesday" << endl; else if (day == 5) cout << "Thursday" << endl; else if (day == 6) cout << "Friday" << endl; else cout << "Saturday" << endl; return 0; }

/* change the filename of a file by rename() function code example. */ /* The C++ <cstdio> rename() function is used to change the name of a file. The file is identified by character string pointed to by oldname. The new filename is identified by character string pointed to by newname. If newname already exists, the behavior of this function is implementation-defined. */ #include <iostream> #include <cstdio> using namespace std; int main() { char oldname[] = "file_old.txt"; char newname[] = "file_new.txt"; /* Deletes the file if exists */ if (rename(oldname, newname) != 0) perror("Error renaming file"); else cout << "File renamed successfully"; 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; }

/* The fclose() function takes a single argument, a file stream which is to be closed. All the data that are buffered but not written are flushed to the OS and all unread buffered data are discarded. Even if the operation fails, the stream is no longer associated with the file. If the file pointer is used after fclose() is executed, the behaviour is undefined. */ /* Close file by fclose() function code example */ #include <iostream> #include <cstdio> using namespace std; int main() { FILE *fp; fp = fopen("file.txt","w"); char str[20] = "Hello World!"; if (fp == NULL) { cout << "Error opening file"; exit(1); } fprintf(fp,"%s",str); fclose(fp); cout << "File closed successfully"; return 0; }

/* 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() }

/* The remove() function in C++ removes a specified file. It is defined in the cstdio header file. */ /* Delete the file whose name is specified in filename by remove() function code example. */ #include <iostream> #include <cstdio> using namespace std; int main() { char filename[] = "C:\\Users\\file.txt"; // deletes the file if it exists int result = remove(filename); // check if file has been deleted successfully if (result != 0) { // print error message cerr << "File deletion failed"; } else { cout << "File deleted successfully"; } return 0; }

/* For output streams (and for update streams on which the last operation was output), writes any unwritten data from the stream's buffer to the associated output device. For input streams (and for update streams on which the last operation was input), the behavior is undefined. If stream is a null pointer, all open output streams are flushed, including the ones manipulated within library packages or otherwise not directly accessible to the program. */ /* flushes the output buffer of the stream by fflush function code example. */ #include <stdio.h> #include <iostream> using namespace std; int main() { char mybuffer[800]; FILE * file; file = fopen ("demo.txt","r+"); fputs ("test",file); fflush (file); // flushing required fgets (mybuffer,800,file); cout << mybuffer << endl; fclose (file); return 0; }

/* 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; }

/* The eof() method of ios class in C++ is used to check if the stream is has raised any EOF (End Of File) error. It means that this function will check if this stream has its eofbit set. */ // C++ code example to demonstrate the working of eof() function #include <iostream> #include <fstream> int main () { std::ifstream is("example.txt"); char c; while (is.get(c)) std::cout << c; if (is.eof()) std::cout << "[EoF reached]\n"; else std::cout << "[error reading]\n"; is.close(); 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; }

/* getche() function is a function in C programming language which waits for any character input from keyboard and it will also echo the input character on to the output screen. Please find below the description and syntax for above file handling function. */ int chcount = 0, wdcount =0, count = 0; char ch=' '; cout << "Enter your text : "; while ( ch != '\r' ) { if ( ch !=' ' ) { chcount++; count++; } else if (count > 2) { wdcount++; count=0; } ch = getche(); } if (count >2) //validate that last word is counted wdcount++; cout<<"\nCount of words is: "<<wdcount<<"\nCount of charcters is: "<<chcount<<"\n"; system("pause"); return 0;