Basic C Programming Storing int to chars

Question

My question is relatively simple but for some reason this bit of simple code perplexes me as to why its not outputting any errors or warnings. Why am I able to store integers in a character array??

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char **argv) {
    char S[256];
    // initialize array
    int i;

    for(i=0; i<256; i++) {
        S[i] = i;
    }

    return 0;
}

Answer 1

I wasn't going to answer this, but every answer that's been posted so far is just close enough to right to be misleading in one way or another.

In C and C++, char is a small integer type that occupies an amount of storage that the C and C++ standards agree to call a byte--but their byte may or may to correspond to what anybody/anything else calls a byte. It is guaranteed to be at least 8 bits, because it must be able to store values from -127 to +127, or else from 0 to 255.

There are two other types named signed char and unsigned char. A char (specified as neither signed nor unsigned) has the same range as either signed char or unsigned char (but there's no guarantee/requirement about which, and many compilers support a flag to switch from one to the other). Although it has the same range as one of the other two, a plain char is still a separate type from either of the other two (e.g., you can have a function overloaded on all three types).

As noted above, char is required to have a range that requires at least 8 bits to store--but it can be larger if an implementation desires (though, in fact, compilers with char larger than 8 bits are actually pretty unusual).

When you assign a value like 1 with type integer to a char, the value is converted (if possible) to the same value represented as a char. If it can't be represented, the conversion will depend on whether a char is signed or unsigned. If it's unsigned, then the value will be reduced modulo 2ⁿ-1, just like other unsigned types. If it's signed, the result isn't guaranteed.

Note that this is a conversion, but not a cast. As defined in either C or C++, a cast is an explicit notation to cause a conversion. The conversion itself is exactly that--a conversion. Without the explicit notation (e.g., (char)i or static_cast<char>(i) in C++) what you have is a conversion but not a cast.

Answer 2

Characters in C are represented as 8-bit integers. There fore you can treat them as integers and vice versa.

// For example:

int a = 3;
char b = 'b';

a = a + b;

printf("%d", b); // prints 98 (ASCII code for 'b')
printf("%d", a); // prints 101 (3 + 98)