Programming

C Types - Character

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Let’s start with the smallest type, char. It is guaranteed to be large enough to hold one byte’s worth, and it’s always fixed size. If people will tell you that a byte is always eight bits, better think again. Every popular hardware architecture indeed uses eight-bit bytes, but there are exceptions, so don’t make assumptions if you want to write portable code. On x86, since a byte is eight bits, a char (unsigned) can hold values from 0 to 255, that is 28. If a char is signed, then it can hold values from -128 to 127. But the name may mislead you: a character can indeed be stored in a char, but if you’re using Unicode, we’re talking multibyte there and you’ll have to use wchar_t, but more on that later.

char and unsigned char have no diferences. Actually on many platforms unqualified char is signed. The same way – e.g. if you have an 8-bit char, 7 bits can be used for magnitude and 1 for sign. So an unsigned char might range from 0 to 255, whilst a signed char might range from -128 to 127 (for example).

In my Fedora Linux:

/* char.c */
#include <stdio.h>
/* Exploring data types */

int main()
{
  char c;
  signed char sc;
  unsigned char uc;

  /* Assignments */
  c = 'a';
  sc = 'b';
  uc = 'c';

  /* Print them as Characters */
  printf("c = %c\n", c);
  printf("sc = %c\n", sc);
  printf("uc = %c\n", uc);

  /* Print them as Integers */
  printf("c = %i\n", c);
  printf("sc = %i\n", sc);
  printf("uc = %i\n", uc);

  return 0;
}

Compiling and running it:

~(gomix) gcc char.c -o char
~(gomix) ./char
c = a
sc = b
uc = c
c = 97
sc = 98
uc = 99