Produce following asterisk using two for loops - c++

Question

I need to produce following pattern using two for loops.
a
aa
aaa
aaaa
aaaaa
aaaaaa
aaaaaaa
I have try this:
#include <iostream>
using namespace std;
int main()
{
int a;
a = 7;
for (int i = 1;i <= a;i++) {
cout << "" << endl;
for (int i = 1;i <= a;i++) {
cout << "*";
}
}
}
But the result is 7 characters in seven rows :(

Answer 1

For starters the task can be done using only one loop. For example
#include <iostream>
#include <iomanip>
int main()
{
while ( true )
{
const char c = '*';
std::cout << "Enter a non-negative number (0 - exit): ";
unsigned int n;
if ( not ( std::cin >> n ) or ( n == 0 ) ) break;
std::cout << '\n';
for ( unsigned int i = 0; i < n; i++ )
{
std::cout << std::setw( i + 2 ) << std::setfill( c ) << '\n';
}
std::cout << '\n';
}
return 0;
}
The program output might look like
Enter a non-negative number (0 - exit): 7
*
**
***
****
*****
******
*******
Enter a non-negative number (0 - exit): 6
*
**
***
****
*****
******
Enter a non-negative number (0 - exit): 5
*
**
***
****
*****
Enter a non-negative number (0 - exit): 4
*
**
***
****
Enter a non-negative number (0 - exit): 3
*
**
***
Enter a non-negative number (0 - exit): 2
*
**
Enter a non-negative number (0 - exit): 1
*
Enter a non-negative number (0 - exit): 0
As for your code then the inner loop outputs exactly 7 characters '*'
for (int i = 1;i <= a;i++) {
cout << "*";
}
So what you do is what you get.
You could write the inner loop for example the following way
for (int j = 0;j < i; j++) {
cout << "*";
}