Trying to make an ASCII table in C++, cannot get the "special characters" to display properly

Question

I'm working on an assignment where I need to print out the ASCII table in the table format exactly like the picture below.

http://i.gyazo.com/f1a8625aad1d55585df20f4dba920830.png I currently can't get the special words/symbols to display (8, 9, 10, 13, 27, 32, 127).

Here it is running: http://i.gyazo.com/80c8ad48ef2993e93ef9b8feb30e53af.png

Here is my current code:

#include <iomanip>
#include <iostream>
using namespace std;

int main()
{

cout<<"ASCII TABLE:"<<endl;
cout<<endl;
for (int i = 0; i < 128; i++)
{
if (i <= 32)
cout << "|" << setw(2)
<<i
<< setw(3)
<< "^" << char (64+i) <<"|";
if (i >= 33)
cout << "|" << setw(3)
<<i
<< setw(3)
<<char (i) << "|";
if((i+1)%8 == 0) cout << endl;
}
return 0;
}

Answer 1

8    Back Space
9    Horizontal Tab
10   New Line
13   carriage return
27   Escape (Esc)
32   Space
127  Del

As Above these ASCII characters doesn't display any visible or printed character. That's why you might be thinking you are not getting these values.

Answer 2

I'm no sure what's your real problem there, but you didn't get an answer yet about how to print the special codes.

Running your programme I see that you have some minor alignment problems. If that's the problem, note that setw(3) only applies to the next element:

    cout << setw(3) << "^" << char (64+i); // prints "  ^A" instead of " ^A". 

If you try to correct into

    cout << setw(3) << "^"+ char (64+i);  // ouch !!!!

you'll get undefined behaviour (garbage) because "^" is a pointer to a string and adding char(64+i) is understood as adding an offset of 64+i to this pointer. As this is a rather random address, you'll get garbage. Use a std::string instead.

The other difference I see between your programme's output and the expected result is that you don't print the code of the special chars. If that's the problem, either use a switch statement (very repetitive here), or a lot of if/else or use an associative map.

Here an alternative proposal putting all this together:

map<char, string>special{ { 8, "BS " }, { 9, "\\t " }, { 10, "\\n " }, { 13, "CR " }, { 27, "ESC" }, { 32, "SP " }, { 127, "DEL" } };
cout << "ASCII TABLE:" << endl << endl;
for (int i = 0; i < 128; i++) {
    cout << "|" << setw(3)<<i<<setw(4);  // setw() only applies to next
    if (iscntrl(i) || isspace(i)) {      // if its a control char or a space
        auto it = special.find(i);       // look if there's a special translation
        if (it != special.end())         // if yes, use it
             cout << it->second;
        else cout << string("^") + char(64 + i)+ string(" ");  // if not, ^x, using strings
    }
    else if (isprint(i))        // Sorry I'm paranoïd: but I always imagine that there could be a non printable ctrl ;-)
        cout << char(i)+string(" ") ;       // print normal char 
    cout << "|";
    if ((i + 1) % 8 == 0) cout << endl;
}

Now some additional advices:

• take the effort to indent
• instead of manual categorization of chars, use iscntrl(), isspace(), isprint(). As long as you only use ascii, it's manageable to do like you did. But as soons as you move to internationalisation and wide chars it becomes increasinlgy cumbersome to do that whereas there are easy wide equivalents like iswcntrl(), iswspace(), iswprint().
• also be rigorous on two consecutive if: If you know that only one of the two should apply, make the effort to write if ... else if these four additional lettes can save you hours of debugging later.