Seeking some clarifications on these codes.

I have the following three short codes with their outputs. I am seeking clarifications as to how the output was come to. Any explanations are welcome. Thanks in advance.

Code:

include <iostream>
using namespace std;
int main()
{
char str[] = "ABKALM!OV";
for (int m=1; str[m]; m=m+2)
cout << str[m];
return 0;

}

Output: BAMO

Code:

include <iostream>
using namespace std;
int main()
{
int arr[] = {1,2,3,4,5};
for (int m=4; m; m=m-1)
arr[m] = arr[m-1] + m;
for (int m=0; m<5; m=m+1)
cout << arr[m];

}

Output: 12468

Code:

include <iostream>
using namespace std;
int main()
{
char arr[]="UND";
try {
for (int m=0; arr[m]; m=m+1) {
cout << arr[m];
if (arr[m]=='N')
throw 3;
cout << arr[m+2];
}
}
catch (…) {
cout << "HOPPLA";
}
cout << arr;
return 0;
}

Output: UDNHOPPLAUND

You need a stop condition for your "for" loops. Instead of

Code:

for (int m=1; str[m]; m=m+2)

it should be

Code:

for (int m=1; m<9; m=m+2)

Also, if you use character arrays like that, you're either going to have to count the number of characters each time you use it or use the "strlen" function. Instead, use "string".

Code:

#include <string>
#include <iostream>

using namespace std;

int main()
{
string str = "ABKALM!OV";
for (int m=0; m < str.size(); m=m+2)
cout << str[m];
return 0;
}

I just wanted to know how that ouput was arrived at. I mean I am just seeking explanations as to what the codes mean that puts out those outputs.

If someone explains it to you, you'll be deprived of the satisfying experience of figuring it out for yourself. Do you have a debugger? If so, run it on these programs, examining variables as you step through the code. That will help you understand how the output was produced. If you don't have a debugger, get paper and pencil, write down the variables, and, as you step through the code, write down the values of the variables as they change. The first one is pretty easy. Do you see the letters of the output "BAMO" in "ABKALM!OV"? Do you see how the for loop selects those letters to be sent to cout?