C++ Program ReadData manipulates a two-dimensional table. #include <iostream> #i

Question

C++

Program ReadData manipulates a two-dimensional table.

#include <iostream>
#include <fstream>
#include <iomanip>
using namespace std;

const int ROW_MAX = 8;
const int COL_MAX = 10;

typedef int ItemType;
typedef ItemType Table[ROW_MAX][COL_MAX];

int main ()
{
Table table;
int rowsUsed;
int colsUsed;
ifstream dataIn;
ofstream dataOut;
int col;
int row;

dataIn.open("debug.dat");
dataOut.open("debug.out");
dataIn >> colsUsed >> rowsUsed;

// Input table values.
for (col = 0; col < colsUsed; col++)
    for (row = 0; row < rowsUsed; row++)
      dataIn >> table[row][col];

// Output table values.
for (row = 0; row < rowsUsed; row++)
{
    for (col = 0; col < colsUsed; col++)
      dataOut << setw(3) << table[row] [col];
    dataOut << endl;
}

return 0;
}

Exercise 1: Program ReadData reads data into a two-dimensional array. The data is input as described in Lesson 11-4, Exercise 1. The data file is shown below: Unfortunately, program ReadData contains an error. Can you find and fix it? Describe the error. Exercise 2: Unless you found two errors at once in Exercise 1, there is still an error lurking in program ReadData. Correct the error and rerun the program. Describe the error.

Explanation / Answer

#include <iostream>
#include <fstream>
#include <iomanip>
#include <string.h>
using namespace std;

const int ROW_MAX = 8;
const int COL_MAX = 10;

typedef int ItemType;
typedef ItemType Table[ROW_MAX][COL_MAX];

int main ()
{
Table table;
int rowsUsed;
int colsUsed;
ifstream dataIn;
ofstream dataOut;
int col;
int row;

// Warning: : table should be memset. it may have some garbage value which will cause inproper output

memset(table,'',sizeof(table));
dataIn.open("debug.dat");

// Error: if file not availabe then also should print error:

if (!dataIn)
{
    cerr << "Unable to open file debug.dat";
    return 0;   // call system to stop
}
dataOut.open("debug.out");
if (!dataOut)
{
    cerr << "Unable to open file debug.out";
    return 0;   // call system to stop
}

dataIn >> colsUsed >> rowsUsed;
/*
Error: ROW_MAX and COL_MAX are define. but if colsUSed and rowsUsed is more than it then it will throw segmentation fault
Example idebug.data:
--------------------
25 25
1 2 3
1 2 3
-------------------
cpu will try to read 25 * 25 data. but table size is not sufficient. so it will show segmentation fault.
*/

if(colsUsed > COL_MAX || rowsUsed > ROW_MAX)
{
   cout<<"MAX size for col: "<<COL_MAX<<"Row: "<< ROW_MAX<<endl;
   cout<<"Invalid size ";
   return 0;
}
// Input table values.
for (col = 0; col < colsUsed; col++)
    for (row = 0; row < rowsUsed; row++)
      if (dataIn >> table[row][col])   // Error: needs to check read is success or not
{
   continue;   // should contineue if read success
}
     else
   break;     // if read fails then no need to read further. if ignore then will give junk value
/*
error:
suppose debug.data is
----------------------
5 5
1 2 3
1 2 3
------------------------

then it will read upto 5 * 5 but actally data is not available. so here needs to print error and return.
*/
if(row != rowsUsed || col != colsUsed)
{
   cout<< "Please check input file. it should have sufficient data ";
   return 0;
}

// Output table values.
for (row = 0; row < rowsUsed; row++)
{
    for (col = 0; col < colsUsed; col++)
      dataOut << setw(3) << table[row] [col];
    dataOut << endl;
}

return 0;
}

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.