What is char , unsigned char , and signed char ?

The char type in C , has a size of 1 byte . The size of a byte , as defined on a given machine , can be viewed by checking the macro CHAR_BITS , in the limits.h header .

/*Excerpt from limits.h */
#define CHAR_BITS 8
/* Define the number of bits in a char */

Typically a byte in C , or on a given machine is formed of 8 bits .

The char type is an integer type , it is used to store the encoding of characters . For example , the encoding of the character a , when a is considered to be part of the ascii character set , is 97 in decimal , or 01100001 in binary . If a is considered to belong to a different character set , it might have a different encoding , as such a variable of the char type , would store a different encoding value for the character a .

The char type can be signed or it can be unsigned , this is implementation defined . The C standard defines , the minimum range that the char type can have , an implementation can define large ranges .

If the char type is unsigned , then it can only contain non negative values , and its minimum range as defined by the C standard is between 0 , and 127 . If the char type is signed , then it can contain 0 , negative , and positive values , and its minimum range as defined by the C standard , is between -127 , and 127 .

Beside the char type in C , there is also the unsigned char , and the signed char types . All three types are different , but they have the same size of 1 byte . The unsigned char type can only store nonnegative integer values , it has a minimum range between 0 and 127 , as defined by the C standard. The signed char type can store , negative , zero , and positive integer values . It has a minimum range between -127 and 127 , as defined by the C standard .

character literals

A character literal , is formed of a character , such as a , enclosed in single quote .

char achar = 'a';

A character literal can contain escape sequences . An escape sequence , is used as a way to represent characters , in the execution character set . For example a new line , that must appear on a console , or on the terminal .

#include<stdio.h>

int main( void){
  char alert = '\a';
  printf( "Hello world %c\n" , alert);}
/* Output : 
Hello world */

Escape sequences , are also used to represent characters , that cannot appear in character literals , such as single quote , or in string literals , such as double quote .

#include<stdio.h>

int main( void){
  char quote = '\'';
  printf( "To quote : %c Limitation , Definition , "
          "Construction , Knowledge , Usability %c \n" ,
          quote,quote);}
/* Output : 
To quote : ' Limitation , Definition , Construction , Knowledge , Usability ' */

Escape sequences , are also used to escape the interpretation of some special characters , such as ? .

#include<stdio.h>

int main( void){
  char escape_interrogation_mark_using_trigraph = '??/?';
  /* ??/ is a trigraph , and is replaced before preprocessing
   by the character \ , so it is as if the character
   literal , is written as '\?'*/
  printf( "%c\n", escape_interrogation_mark_using_trigraph);}
/* Output : 
? */

Escape sequences , are also used , as a way to input characters , by entering their encoding , instead of the character itself .

#include<wchar.h>

int main( void){

  char character = '\141'; // a
  character = '\x61'; // a

  wchar_t wide_character = L'\7'; // alert
  wide_character = L'\x0000ab11'; /* ꬑ  */}

Escape sequences , can also be used , as a way to enter a character universal name , in this case , the character must be a wide character type .

#include<wchar.h>

int main( void){
  wchar_t wide_character = L'\u0800'; /* Samaritan letter alaf */
  wide_character = L'\U00000800'; /* Samaritan letter alaf */ }

Since , signed char , unsigned char , and char , and wide characters , are integer types , they can be initialized by using an integer literal . The integer literal in such a case , hold the value of the encoding of the character .

#include<uchar.h>

int main( void){
  unsigned char x = 97;
  /* 97 , is the encoding of the
     character a , in ascii  */
  char16_t wide_character = 97;}