Sams Teach Yourself C++ in 21 Days

More on Program Flow 195

7

The important idea here is that by using a nested loop, the inner loop is executed for

each iteration of the outer loop. Thus, the character is printed columnstimes for

each row.

As an aside, many C++ programmers use the letters iand jas counting vari-

ables. This tradition goes all the way back to FORTRAN, in which the letters

i, j, k, l, m, and nwere the only counting variables.

Although this might seem innocuous, readers of your program can become

confused by the purpose of the counter, and might use it improperly. You

can even become confused in a complex program with nested loops. It is

better to indicate the use of the index variable in its name—for instance,

CustomerIndexor InputCounter.

NOTE

Scoping in forLoops ....................................................................................

In the past, variables declared in the forloop were scoped to the outer block. The

American National Standards Institute (ANSI) standard changes this to scope these vari-

ables only to the block of the forloop itself; however, not every compiler supports this

change. You can test your compiler with the following code:

#include <iostream>

int main()

{

// i scoped to the for loop?

for (int i = 0; i<5; i++)

{

std::cout << “i: “ << i << std::endl;

}

i = 7; // should not be in scope!

return 0;

}

If this compiles without complaint, your compiler does not yet support this aspect of the

ANSI standard.

If your compiler complains that iis not yet defined (in the line i=7), your compiler does

support the new standard. You can write code that will compile on either compiler by

declaring ioutside of the loop, as shown here:

#include <iostream>

int main()

{