Arrays are often considered to be difficult to use in C++, but this article shows that this is not the case- it even shows how to calculate the number of array elements.
Many programmers who are new to C++ find arrays a difficult subject areas; and often that is because they are under the misconception that:
C++ arrays are difficult to create
C++ arrays are difficult to manipulate
it is not possible to calculate how long a C++ arrays is
This article will show, with some simple examples, that none of those are true.
Using Simple Arrays in a C++ Program
Arrays are easy to create and, in fact, there are two ways of creating a C++ array:
create an array of a set length and add items to it
create an array by assigning a set of items to it
This simple program shows both of those methods in action:
#include <iostream>
#include <string>
using namespace std;
#define LIST_LENGTH 5
int age [] = {16, 2, 77, 40, 12};
string name[LIST_LENGTH];
int i;
int total_age = 0, average_age = 0;
int main ()
{
name [0] = "Jane";
name [1] = "Fred";
name [2] = "Mary";
name [3] = "Henry";
name [4] = "John";
for ( i=0 ; i<LIST_LENGTH ; i++ )
{
cout << name[i] << ": " << age[i] << "\r\n";
total_age += age[i];
}
average_age = total_age/LIST_LENGTH;
cout << "Average Age: " << average_age << "\r\n";
return 0;
}
If this program is compiled and run then it will give the following result:
$ g++ -o array_01 array_01.cpp
$ ./array_01
Jane: 16
Fred: 2
Mary: 77
Henry: 40
John: 12
Average Age: 29
With simple arrays dealt with it's time to look at the much more difficult multidimensional arrays.
Using Multidimensional Arrays in a C++ Program
In actual fact multidimensional Arrays actually aren't any more difficult to work with than simple arrays, as another simple example shows:
#include <iostream>
#include <string>
using namespace std;
#define LIST_LENGTH 3
#define FIELDS 2
int person [LIST_LENGTH][FIELDS] = {{16, 20000},{20,63000},{60,90400}};
And again, the result can be seen by compiling and running this new program:
$ g++ -o array_02 array_02.cpp
$ ./array_02
Average Age: 32
Average Salary: 57800
Calculating the Size of an Array in a C++ Program
In both of the examples so far the program has to be told exactly how long the array is, and (as everyone knows) if any attempt is made to read or write to the array outside of its assigned range will cause the program to crash. So here's the problem - how to test how many items there are in an array if there's no way to find out where the end of the array is. The answer is surprisingly simple - the sizeof method.
The sizeof method calculate the size (in bytes) of a variable, therefore in this case it's simply a matter of dividing the size of the array by the size of the data type used in the array:
cout << "There are " << array_length << " people....\r\n";
for ( i=0 ; i<array_length ; i++ )
{
cout << name[i] << "\r\n";
}
return 0;
}
And, like the other examples, the program can be compiled and run to see the end result:
$ g++ -o array_03 array_03.cpp
$ ./array_03
There are 7 people....
Jane
Fred
Mary
Bill
Barney
William
Sue
Conclusion
The examples in this article are very simple, but do show just how easy it is to work with arrays in C++.
The copyright of the article An Introduction to Using C++ Arrays in C Programming is owned by Mark Alexander Bain. Permission to republish An Introduction to Using C++ Arrays in print or online must be granted by the author in writing.
