.  while(! infile.eof()) 2.  for(int x = 0; x < 1000000; x++) 3.  while(infile >> n)

Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
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Assume that infile has been properly defined to read data from a file and that a file of integers has been properly opened. If you don't know how many integers are in the file, which loop(s) would be appropriate to read in all the values from the file? Variable n has been defined as an int.

1.  while(! infile.eof())

2.  for(int x = 0; x < 1000000; x++)

3.  while(infile >> n)

Answers:

A. 

Both 2 and 3

 

B. 

1, 2, and 3

 

C. 

Both 1 and 2

 

D. 

Both 1 and 3

 

E. 

3 only

Expert Solution
Step 1

Reading integers from the file

To read a file, we need to follow these steps:

  • Include required header files in your C++ program that is #include <fstream>.
  • Declaration of the input file stream 
    • ifstream infile;
  • Open the file from where you want to read integers.
  • Check if the file is opened correctly or not.
  • Start reading from the input stream using eof() function or ">>" operator.
  • Closing the input stream after reading.

 

 

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