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I mean only main function. I dont understand int(c) when(when is not part of the code) c is char. How doeas it work?

#include <iostream>
using namespace std;

int main()
{
 char c;
 cout << "Enter a character: ";
 cin >> c;
 cout << "ASCII Value of " << c << " is " << int(c);
 return 0;
}
Sosos Sojowy
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    Please open your text-book on the chapter or section about *conversions* and *type casting*. – Some programmer dude Jan 21 '21 at 07:21
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    It converts the char to an integer using the char's *encoding*, and then outputs the integer. The bit about `ASCII` is a bug, C++ doesn't require the use of ASCII. – john Jan 21 '21 at 07:27

2 Answers2

3

There is a table(the ASCII table), which stores a map from int to char(this is how chars are represented). The ASCII value of a char is actually the int key of that char in this table. Casting a char into int - int(c) - gives you this int key(ASCII Value of c).

Nikolay Karashtranov
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Can someone explain to me whats happening in this code step by step, c++

Yes. You first need to read a good C++ programming book.

Then you could read some C++ standard, perhaps n3337 or newer. In particular about casts expressions §5.4.

Look also into this C++ reference website. About explicit casts. Some people prefer reinterpret_cast<int>(c) to (int)c for readability reasons.

Read also the documentation of your C compiler, e.g. GCC. You would want to invoke it as g++ -Wall -Wextra -g.

You could also run g++ -Wall -Wextra -O -fverbose-asm your-code.cc and look into the assembler code your-code.s. Probably, that emitted assembler code won't change much if you replace (int)c by reinterpret_cast<int>(c)

Once the compiler gives no warnings, use the debugger, e.g. GDB to understand the behavior of your program.

Your cast (int)c shows a integer (for example 65). Without it, it shows a character (for example A - for the same value c - in your computer the (char)65 -and in all mines, -both at work, rented as VPS, in my pocket -my phone-, and at home- is exactly the literal 'A' unless your computer is not using ASCII -or its superset UTF8-. Today that is uncommon: few computers are using EBCDIC).

The debugger would give you the same information, and the ability to run your code step by step. Since GDB has a step command. So learning to use GDB will win you a lot of work.

Notice that in 2021 UTF-8 is used everywhere, and things are more complex if you want to accept inputs like µ or § or é or °. On my AZERTY keyboard, I can type that with a single keystroke. And € can be typed easily too... These characters are not ASCII!

You could also use the Clang static analyzer (or, in spring 2021, Bismon), and perhaps some C++ variant of Frama-C, perhaps called Frama-Clang. The DECODER project could be useful too.

In theory, A might not be encoded as 65. In the 1970s I programmed on punched cards, and at that time the encoding was EBCDIC. Today you need to got into computer museums to find computers which don't encode the A character as the 65 decimal number, or 0x41 in hexadecimal. Some computers are still using EBCDIC, but I never met such a computer in this century.

Basile Starynkevitch
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