Why my matrix array will stop working when I compile it??.

[bandong123]

#include<iostream>
#include<iomanip>
using namespace std;
int main(){
    int a,b;
    int Rowsize , Colsize ;
    int A[Rowsize][Colsize];
 
    cout<<"Enter number of Row: ";
    cin>>a;
    Rowsize=a;
    cout<<"Enter number of Colums ";
    cin>>b;
    Colsize=b;
 
    for(int Row = 0; Row < Rowsize; Row++)
         for(int Col=0;Col<Colsize;Col++)
    {
                                cout<<"\nEnter A [ "<<Row
                                    <<"][" << Col <<"]: ";
                                    cin>> A[Row][Col];
                                    }
 
    cout<<"\nContents of matrix A:\n";
    for(int Row= 0;Row < Rowsize; Row++)
    {
           for (int Col = 0; Col < Colsize;Col++)
           cout<< setw(4) << A[Row][Col];
           cout<< endl;
}
system("pause");
return 0;
}

[Banfa]

You need to give us more information when you post a question.

• Do you mean it doesn't compile or the compiler produces errors or warnings? Then post the compiler output.
• Do you mean it compiled (possibly with warnings)? Then if warns are produced post them otherwise post the output of your code when run.
• Post something other than just your code to let us know what is happening, a detailed explaination of what is happening.

I notice that at line 6 you declare Rowsize and Colsize without initialising them, then at line 7 you declare the array A using Rowsize and Colsize as array sizes. This is an error, you have no idea what size the array A will be, anything from 0 to sqr(MAX_INT) including a lot of negative values which are just undefined behaviour.

Try moving the declaration of A to a point in the code after a value has been assigned to Rowsize and Colsize.