Actually, A to Z is guarinteed to be consecutive.
Code:
5.2.1 Character sets
1 Two sets of characters and their associated collating sequences shall be defined: the set in
which source files are written (the source character set), and the set interpreted in the
execution environment (the execution character set). Each set is further divided into a
basic character set, whose contents are given by this subclause, and a set of zero or more
locale-specific members (which are not members of the basic character set) called
extended characters. The combined set is also called the extended character set. The
values of the members of the execution character set are implementation-defined.
2 In a character constant or string literal, members of the execution character set shall be
represented by corresponding members of the source character set or by escape
sequences consisting of the backslash \ followed by one or more characters. A byte with
all bits set to 0, called the null character, shall exist in the basic execution character set; it
is used to terminate a character string.
3 Both the basic source and basic execution character sets shall have the following
members: the 26 uppercase letters of the Latin alphabet
A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z
the 26 lowercase letters of the Latin alphabet
a b c d e f g h i j k l m
n o p q r s t u v w x y z
the 10 decimal digits
0 1 2 3 4 5 6 7 8 9
the following 29 graphic characters
! " # % & ' ( ) * + , - . / :
; < = > ? [ \ ] ^ _ { | } ~
the space character, and control characters representing horizontal tab, vertical tab, and
form feed. The representation of each member of the source and execution basic
character sets shall fit in a byte. In both the source and execution basic character sets, the
value of each character after 0 in the above list of decimal digits shall be one greater than
the value of the previous.
Read the last line.
Quzah.