CS Programming2 1 st Semester H Sheet # 8 File Processing. Princess Nora University College of Computer and Information Sciences

Transcription

1 Princess Nora University College of Computer and Information Sciences CS Programming2 1 st Semester H Sheet # 8 File Processing Question#1 Write line of code to do the following: 1- Open "boot" file to write? ofstream outbootfile("boot.dat",ios::out); 2- Display record in boot file? boot boot1; outbootfile.read(reinterpret_cast< char *>(&boot1),sizeof(boot)); 3-Write statement to boot file ("boot1",2231,"black")? outfile.write(reinterpret_cast< char *>(&boot1),sizeof(boot))) 4-Read first statement from boot file? boot.read(reinterpret_cast< char *>(&boot1),sizeof(boot)); 5-Close this file? outclientfile.close(); Question#2 Find the errors and correct them in each statement: a) outpayable<<account<<company<<amount<<endl; Error: the file payables.dat can't open before the attempt is made to output data to the stream. Correction: use stream function open to open payable.dat for output. b) inreceivable>>account>>company>>amount; Error: the incorrect stream object is being used to read a record from the file named payables.dat; Correction: use stream object in payable to refer to payables.dat. c) ofstream outtools("tools.dat",ios::out); Error: the file's contents are discarded because the file is opened for output (ios::out). Correction: to add to the file, open the file either for updating (ios::ate) or for appending (ios::app).

2 Question#3 1- Write a C++ program to write number 1 to 100 in a data file NOTES.TXT. #include<fstream.h> int main() ofstream fout; fout.open("notes.txt"); for(int i=1;i<=100;i++) fout<<i<<endl; fout.close(); return 0; 2- Write a C++ program, which initializes a string variable to the content "Time is a great teacher but unfortunately it kills all its pupils. Berlioz" and outputs the string to the disk file OUT.TXT. you have to include all the header files if required. #include<fstream.h> int main() ofstream fout; fout.open("out.txt"); char str[300]="time is a great teacher but unfortunately it kills all its pupils. Berlioz"; fout<<str; fout.close(); return 0;

3 3- Write a function to count the number of blank present in a text file named "OUT.TXT". void blankspace() ifstream fin; fin.open("out.txt"); char ch; int count=0; while(!fin.eof()) fin.get(ch); /* get()>> Extracts a single character from the stream.*/ if(ch==' ') count++; cout<<"number of blank spaces in file are "<<count; fin.close(); 4- Write a function to count number of words in a text file named "OUT.TXT". void countwords() ifstream fin ; fin.open("out.txt"); char word[30]; int count=0; while(!fin.eof()) fin>>word; count++; cout<<"number of words in file are "<<count; fin.close();

4 5- Write a function in C++ to print the count of word theas an independent word in a text file STORY.TXT. for example, if the content of the file STORY.TXT is There was a monkey in the zoo. The monkey was very naughty. Then the output of the program should be 2. void countword() ifstream fin; fin.open("story.txt"); char word[30]; int count=0; while(!fin.eof()) fin>>word; if(strcmpi(word,"the")==0) /* strcmp()>> Compare two strings, If both strings are equal then it gives the result as zero */ count++; cout<<"number of the word in file are "<<count; fin.close(); 6- Write a function in C++ to count and display the number of lines not starting with alphabet 'A' present in a text file "STORY.TXT". Example: If the file "STORY.TXT" contains the following lines, The rose is red. A girl is playing there. There is a playground. An airplane is in the sky. Numbers are not allowed in the password. The function should display the output as 3. void countlines()

5 ifstream fin; fin.open("story.txt"); char str[80]; int count=0; while(!fin.eof()) fin.getline(str,80); if(str[0]!='a') count++; cout<<"number of lines not starting with A are "<<count; fin.close(); Binary File in C++ class student int admno; char name[20]; public: void getdata() cout<<"\nenter The admission no. "; cin>>admno; cout<<"\n\nenter The Name of The Student "; gets(name);// Read string (function ) ; void showdata() cout<<"\nadmission no. : "<<admno; cout<<"\nstudent Name : "; puts(name);// Write string (function ) int retadmno() return admno; According to the previous class Create the following functions:

6 7- function to write in a binary file void write_data() ofstream fp2; fp2.open("student.dat",ios::binary ios::app); obj.getdata(); fp2.write((char*)&obj,sizeof(obj)); fp2.close(); 8- function to display records of file void display() ifstream fp1; fp1.open("student.dat",ios::binary); while(fp1.read((char*)&obj,sizeof(obj))) obj.showdata(); fp1.close(); 9- Function to search and display from binary file void search (int n) ifstream fp1; fp1.open("student.dat",ios::binary); while(fp1.read((char*)&obj,sizeof(obj))) if(obj.retadmno()==n) obj.showdata();

7 fp1.close(); 10- Function to delete a record void deleterecord(int n) ifstream fp1; fp1.open("student.dat",ios::binary); ofstream fp2; fp2.open("temp.dat",ios::out ios::binary); while(fp1.read((char*)&obj,sizeof(obj))) if(obj.retadmno()!=n) fp2.write((char*)&obj,sizeof(obj)); fp1.close(); fp2.close(); remove("student.dat"); rename("temp.dat","student.dat"); 11- Function to modify a record void modifyrecord(int n) student"; fstream fp; int found=0; fp.open("student.dat",ios::in ios::out); while(fp.read((char*)&obj,sizeof(obj)) && found==0) if(obj.retadmno()==n) obj.showdata(); cout<<"\nenter The New Details of fp.write((char*)&obj,sizeof(obj)); found=1; obj.getdata(); int pos=-1*sizeof(obj); fp.seekp(pos,ios::cur);

8 fp.close(); 12- Write a program that use two files one named file1.txt and the other file2.txt, file1.txt should has lines of text. The program copy the file1.txt to file2.txt line by line using copy() function that receives two file stream and a binary copy operation is performed. #include <iostream> #include <fstream> #include <iomanip> using namespace std; void copy (istream& is, ostream& os); void main() ifstream infile("file1.txt",ios::in ios::binary ); ofstream outfile("file2.txt", ios::out ios::binary ); if (!infile.is_open()!outfile.is_open()) cout<<"file could not be opened!"<<endl; exit(1); copy(infile,outfile); outfile.close(); infile.close(); void copy(istream& is, ostream& os) char line[80]; while (is.getline(line,80)) os<<line<<endl;