Character Functions

Character Functions

Date: November 3, 2018
Author: Paul Lewallen
Category:
isalpha(c)Description:
Returns true if c is alphabetic: a-z or A-Z.

Ex.
isalpha('A'); // Returns true
isalpha(myString[0]); // Returns true because 'H' is alphabetic
isalpha(myString[3]); // Returns false because '9' is not alphabetic
isdigit(c)Description:
Returns true if c is a numeric digit: 0-9.

Ex.
isdigit(myString[3]); // Returns true because '9' is numeric
isdigit(myString[4]); // Returns false because ! is not numeric
isalnum(c)Description:
Returns true if c is alphabetic or a numeric digit. Thus, returns true if either isalpha or isdigit would return true.

Ex.
isalnum('A'); // Returns true
isalnum(myString[3]); // Returns true because '9' is numeric
isspace(c)Description:
Returns true if character c is a whitespace.

Ex.
isspace(myString[5]); // Returns true because that character is a space ' '.
isspace(myString[0]); // Returns false because 'H' is not whitespace.
islower(c)Description:
Returns true if character c is a lowercase letter a-z.

Ex.
islower(myString[0]); // Returns false because 'H' is not lowercase.
islower(myString[1]); // Returns true because 'e' is lowercase.
islower(myString[3]); // Returns false because '9' is not a lowercase letter.
isupper(c)Description:
Returns true if character c is an uppercase letter A-Z.

Ex.
isupper(myString[0]); // Returns true because 'H' is not uppercase.
isupper(myString[1]); // Returns false because 'e' is lowercase.
isupper(myString[3]); // Returns false because '9' is not an uppercase letter.
isblank(c)Description:
Returns true if character c is a blank character. Blank characters include spaces and tabs.

Ex.
isblank(myString[5]); // Returns true because that character is a space ' '.
isblank(myString[0]); // Returns false because 'H' is not blank.
isxdigit(c)Description:
Returns true if c is a hexadecimal digit: 0-9, a-f, A-F.

Ex.
isxdigit(myString[3]); // Returns true because '9' is a hexadecimal digit.
isxdigit(myString[1]); // Returns true because 'e' is a hexadecimal digit.
isxdigit(myString[6]); // Returns false because 'G' is not a hexadecimal digit.
ispunct(c)Description:
Returns true if c is a punctuation character. Punctuation characters include: !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~

Ex.
ispunct(myString[4]); // Returns true because '!' is a punctuation character.
ispunct(myString[6]); // Returns false because 'G' is not a punctuation character.
isprint(c)Description:
Returns true if c is a printable character. Printable characters include alphanumeric, punctuation, and space characters.

Ex.
isprint(myString[0]); // Returns true because 'H' is a alphabetic.
isprint(myString[4]); // Returns true because '!' is punctuation.
isprint(myString[5]); // Returns true because that character is a space ' '.
isprint('\0'); // Returns false because the null character is not printable
iscntrl(c)Description:
Returns true if c is a control character. Control characters are all characters that are not printable.

Ex.
iscntrl(myString[0]); // Returns false because 'H' is a not a control character
iscntrl(myString[5]); // Returns false because space is a not a control character
iscntrl('\0'); // Returns true because the null character a control character
isalpha(c)Description:
'true' if alphabetic
(a-z or A-Z)

Ex.
isalpha('x') // true
isalpha('6') // false
isalpha('!') // false
isdigit(c)Description:
'true' if digit (0-9)

Ex.
isdigit('x') // false
isdigit('6') // true
isspace(c)Description:
true if whitespace

Ex.
isspace(' ') // true
isspace('\n') // true
isspace('x') // false
toupper(c)Description:
Uppercase version

Ex.
toupper('a') // A
toupper('A') // A
toupper('3') // 3
tolower(c)Description:
Lowercase version

Ex.
tolower('A') // a
tolower('a') // a
tolower('3') // 3

char myString[30] = “Hey9! Go”;

toupper(c)Description:
If c is a lowercase alphabetic character (a-z), returns the uppercase version (A-Z). If c is not a lowercase alphabetic character, just returns c.

Ex.
toupper(myString[0]); // Returns 'H' (no change)
toupper(myString[1]); // Returns 'E' ('e' converted to 'E')
toupper(myString[3]); // Returns '9' (no change)
toupper(myString[5]); // Returns ' ' (no change)
tolower(c)Description:
If c is an uppercase alphabetic character (A-Z), returns the lowercase version (a-z). If c is not an uppercase alphabetic character, just returns c.

Ex.
tolower(myString[0]); // Returns 'h' ('H' converted to 'h')
tolower(myString[1]); // Returns 'e' (no change)
tolower(myString[3]); // Returns '9' (no change)
tolower(myString[5]); // Returns ' ' (no change)