Issue in C++ Arrays

Question

I am trying to do some homework and I am running into a problem. My homework is

•Using a for loop, print the contents of the array.

The output should appear like this:

PRINTING CONTENTS OF ARRAY

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

I have my code and it is working. However at the end of my alphabet a bunch of random characters and symbols appear. Is there anything you guys see that I am doing wrong?

Here is my code.

#include <iostream>
using std::cin;
using std::cout;
using std::endl;
// main FUNCTION BEGIN PROGRAM EXECUTION
int main()
{
// ALPHABET ARRAY DECLARATIONS
char Letters [26] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};
for (int i = 0; i < 27 ; i++)
{
cout<< "PRINTING CONTENTS OF ARRAY" << endl;
cout<< "===============================" << endl;
cout<< Letters << " ";
cout<< endl;
break;
}
return 0 ;
} // ***END main FUNCTION***

Basically the problem to put it simply is that it prints A-Z like I want it to but also prints a bunch of random symbols after Z. Any Ideas? As I am new to this I am sure it's probably something simple. Thanks in advance!

• Rapptz: You have an off-by-one error.
• Thomas: But that's besides the point, right? Jack isn't actually looping. Doesn't the << need a null terminated character array?
• Rapptz: You also have break; in there for no reason. You know that breaks the for loop right?

Answer 1

When you are passing an array of characters to an output stream, the array must be null terminated. Your array is not null terminated; that's why you get extra garbage at the end.

However, this is not the main problem of your solution: you need to index letters, like this:

cout << Letters[i] << " ";

Finally, with 26 letters, indexes go zero to 25, so the loop continuation condition should be i < 26, i != 26, or i <= 25.

• Jack: Thank you. Josephs comment showed me how to do what you stated! I appreciate the help!
• Jack: Ah I see what you mean! I will check into that and see what happens. I got the desired print out but from what I understand it is still wrong. ^_^
• Jack: I made the changes Letters[i] and i < 26 and it simply prints only A now
• Sergey Kalinichenko: @Jack That's because you need to remove the break. What happens when you have a break is that the loop is effectively gone: it goes through the first iteration, and drops out immediately without going back.

Answer 2

To remove the "bunch of random characters and symbols", add a NUL to the end of Letters:

char Letters [] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 
 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 
 'U', 'V', 'W', 'X', 'Y', 'Z', 0};

This is will print the alphabet 26 times, which may not be what you want. Edit: Previous statement wrong--I missed your break;.

• Jack: This actually fixed my problem Thank you so much! I switched Letters [26] to [27] added the 0 and it worked like a charm! I appreciate it!
• Sergey Kalinichenko: @Jack How could this possibly fix your problem, if you end up with 27 printouts instead of just one? ;-)
• Qaz: @dasblinkenlight, The break statement :(
• Sergey Kalinichenko: @chris Isn't it funny how two wrongs sometimes make a right? The teacher is not going to like this solution, though :)
• Jack: I am not sure. I am still new. However when I added the 0 after Z in the array it gave me an error: to many intializer values. I changed the 26 to 27 and it fixed the problem. If I had to guess I would say the 27th null terminated the array as das stated above. I will put this as my accepted answer when the 9 minute time ends.

Answer 3

Add a null at the end of array. c functions checks for a null character to terminate.

Answer 4

Array index starts from 0 to N, you have 26 characters in Letters, the index starts from 0 to 25:

cout<< "PRINTING CONTENTS OF ARRAY" << endl;
cout<< "===============================" << endl;
for (int i = 0; i < 26 ; i++)
{
 cout<< Letters[i] << " ";
}
cout<< endl;

break; is normally used to break for or while loop under certain condition. You for loopfinishes smoothly, you don't need abreak` in the loop.

• Jack: Thanks billz, I changed it but it is still giving me the same problem. After Z it is printing a bunch of symbols.
• billz: @Jack, sorry I had typo, I've fixed it

Answer 5

char arrays in C++ are null terminated and starts from zero based index hence when you intialise the array

char Letters [26] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};

You did not take into account that you require 1 more space for '0円' to terminate the array which causes undefined behaviour

Since you print Letters[0] to Letters[26], you are again causing undefined behaviour when you write Letters[26] hence the appearance of rubbish values