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### 21.3 Characters

Most of the characters in the ASCII character set may be referred to by name: for example, #\tab, #\esc, #\stx, and so on. The following table describes the ASCII names for each character.

 0 = #\nul 1 = #\soh 2 = #\stx 3 = #\etx 4 = #\eot 5 = #\enq 6 = #\ack 7 = #\bel 8 = #\bs 9 = #\ht 10 = #\nl 11 = #\vt 12 = #\np 13 = #\cr 14 = #\so 15 = #\si 16 = #\dle 17 = #\dc1 18 = #\dc2 19 = #\dc3 20 = #\dc4 21 = #\nak 22 = #\syn 23 = #\etb 24 = #\can 25 = #\em 26 = #\sub 27 = #\esc 28 = #\fs 29 = #\gs 30 = #\rs 31 = #\us 32 = #\sp

The delete character (octal 177) may be referred to with the name #\del.

Several characters have more than one name:

• #\space, #\sp
• #\newline, #\nl
• #\tab, #\ht
• #\backspace, #\bs
• #\return, #\cr
• #\page, #\np
• #\null, #\nul

 char? x Scheme Procedure scm_char_p (x) C Function
 Return #t iff x is a character, else #f.

 char=? x y Scheme Procedure
 Return #t iff x is the same character as y, else #f.

 char
 Return #t iff x is less than y in the ASCII sequence, else #f.

 char<=? x y Scheme Procedure
 Return #t iff x is less than or equal to y in the ASCII sequence, else #f.

 char>? x y Scheme Procedure
 Return #t iff x is greater than y in the ASCII sequence, else #f.

 char>=? x y Scheme Procedure
 Return #t iff x is greater than or equal to y in the ASCII sequence, else #f.

 char-ci=? x y Scheme Procedure
 Return #t iff x is the same character as y ignoring case, else #f.

 char-ci
 Return #t iff x is less than y in the ASCII sequence ignoring case, else #f.

 char-ci<=? x y Scheme Procedure
 Return #t iff x is less than or equal to y in the ASCII sequence ignoring case, else #f.

 char-ci>? x y Scheme Procedure
 Return #t iff x is greater than y in the ASCII sequence ignoring case, else #f.

 char-ci>=? x y Scheme Procedure
 Return #t iff x is greater than or equal to y in the ASCII sequence ignoring case, else #f.

 char-alphabetic? chr Scheme Procedure scm_char_alphabetic_p (chr) C Function
 Return #t iff chr is alphabetic, else #f. Alphabetic means the same thing as the isalpha C library function.

 char-numeric? chr Scheme Procedure scm_char_numeric_p (chr) C Function
 Return #t iff chr is numeric, else #f. Numeric means the same thing as the isdigit C library function.

 char-whitespace? chr Scheme Procedure scm_char_whitespace_p (chr) C Function
 Return #t iff chr is whitespace, else #f. Whitespace means the same thing as the isspace C library function.

 char-upper-case? chr Scheme Procedure scm_char_upper_case_p (chr) C Function
 Return #t iff chr is uppercase, else #f. Uppercase means the same thing as the isupper C library function.

 char-lower-case? chr Scheme Procedure scm_char_lower_case_p (chr) C Function
 Return #t iff chr is lowercase, else #f. Lowercase means the same thing as the islower C library function.

 char-is-both? chr Scheme Procedure scm_char_is_both_p (chr) C Function
 Return #t iff chr is either uppercase or lowercase, else #f. Uppercase and lowercase are as defined by the isupper and islower C library functions.

 char->integer chr Scheme Procedure scm_char_to_integer (chr) C Function
 Return the number corresponding to ordinal position of chr in the ASCII sequence.

 integer->char n Scheme Procedure scm_integer_to_char (n) C Function
 Return the character at position n in the ASCII sequence.

 char-upcase chr Scheme Procedure scm_char_upcase (chr) C Function
 Return the uppercase character version of chr.

 char-downcase chr Scheme Procedure scm_char_downcase (chr) C Function
 Return the lowercase character version of chr.