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The Fortran language can treat characters as single character or contiguous strings.
Characters could be any symbol taken from the basic character set, i.e., from the letters, the decimal digits, the underscore, and 21 special characters.
A character constant is a fixed valued character string.
The intrinsic data type character stores characters and strings. The length of the string can be specified by len specifier. If no length is specified, it is 1. You can refer individual characters within a string referring by position; the left most character is at position 1.
Character Declaration
Declaring a character type data is same as other variables −
type-specifier :: variable_name
For example,
character :: reply, sex
you can assign a value like,
reply = ‘N’ sex = ‘F’
The following example demonstrates declaration and use of character data type −
program hello implicit none character(len = 15) :: surname, firstname character(len = 6) :: title character(len = 25)::greetings title = ''Mr. '' firstname = ''Rowan '' surname = ''Atkinson'' greetings = ''A big hello from Mr. Bean'' print *, ''Here is '', title, firstname, surname print *, greetings end program hello
When you compile and execute the above program it produces the following result −
Here is Mr. Rowan Atkinson A big hello from Mr. Bean
Concatenation of Characters
The concatenation operator //, concatenates characters.
The following example demonstrates this −
program hello implicit none character(len = 15) :: surname, firstname character(len = 6) :: title character(len = 40):: name character(len = 25)::greetings title = ''Mr. '' firstname = ''Rowan '' surname = ''Atkinson'' name = title//firstname//surname greetings = ''A big hello from Mr. Bean'' print *, ''Here is '', name print *, greetings end program hello
When you compile and execute the above program it produces the following result −
Here is Mr.Rowan Atkinson A big hello from Mr.Bean
Some Character Functions
The following table shows some commonly used character functions along with the description −
| Sr.No | Function & Description |
|---|---|
| 1 |
len(string) It returns the length of a character string |
| 2 |
index(string,sustring) It finds the location of a substring in another string, returns 0 if not found. |
| 3 |
achar(int) It converts an integer into a character |
| 4 |
iachar(c) It converts a character into an integer |
| 5 |
trim(string) It returns the string with the trailing blanks removed. |
| 6 |
scan(string, chars) It searches the “string” from left to right (unless back=.true.) for the first occurrence of any character contained in “chars”. It returns an integer giving the position of that character, or zero if none of the characters in “chars” have been found. |
| 7 |
verify(string, chars) It scans the “string” from left to right (unless back=.true.) for the first occurrence of any character not contained in “chars”. It returns an integer giving the position of that character, or zero if only the characters in “chars” have been found |
| 8 |
adjustl(string) It left justifies characters contained in the “string” |
| 9 |
adjustr(string) It right justifies characters contained in the “string” |
| 10 |
len_trim(string) It returns an integer equal to the length of “string” (len(string)) minus the number of trailing blanks |
| 11 |
repeat(string,ncopy) It returns a string with length equal to “ncopy” times the length of “string”, and containing “ncopy” concatenated copies of “string” |
Example 1
This example shows the use of the index function −
program testingChars
implicit none
character (80) :: text
integer :: i
text = ''The intrinsic data type character stores characters and strings.''
i=index(text,''character'')
if (i /= 0) then
print *, '' The word character found at position '',i
print *, '' in text: '', text
end if
end program testingChars
When you compile and execute the above program it produces the following result −
The word character found at position 25 in text : The intrinsic data type character stores characters and strings.
Example 2
This example demonstrates the use of the trim function −
program hello implicit none character(len = 15) :: surname, firstname character(len = 6) :: title character(len = 25)::greetings title = ''Mr.'' firstname = ''Rowan'' surname = ''Atkinson'' print *, ''Here is'', title, firstname, surname print *, ''Here is'', trim(title),'' '',trim(firstname),'' '', trim(surname) end program hello
When you compile and execute the above program it produces the following result −
Here isMr. Rowan Atkinson Here isMr. Rowan Atkinson
Example 3
This example demonstrates the use of achar function −
program testingChars
implicit none
character:: ch
integer:: i
do i = 65, 90
ch = achar(i)
print*, i, '' '', ch
end do
end program testingChars
When you compile and execute the above program it produces the following result −
65 A 66 B 67 C 68 D 69 E 70 F 71 G 72 H 73 I 74 J 75 K 76 L 77 M 78 N 79 O 80 P 81 Q 82 R 83 S 84 T 85 U 86 V 87 W 88 X 89 Y 90 Z
Checking Lexical Order of Characters
The following functions determine the lexical sequence of characters −
| Sr.No | Function & Description |
|---|---|
| 1 |
lle(char, char) Compares whether the first character is lexically less than or equal to the second |
| 2 |
lge(char, char) Compares whether the first character is lexically greater than or equal to the second |
| 3 |
lgt(char, char) Compares whether the first character is lexically greater than the second |
| 4 |
llt(char, char) Compares whether the first character is lexically less than the second |
Example 4
The following function demonstrates the use −
program testingChars
implicit none
character:: a, b, c
a = ''A''
b = ''a''
c = ''B''
if(lgt(a,b)) then
print *, ''A is lexically greater than a''
else
print *, ''a is lexically greater than A''
end if
if(lgt(a,c)) then
print *, ''A is lexically greater than B''
else
print *, ''B is lexically greater than A''
end if
if(llt(a,b)) then
print *, ''A is lexically less than a''
end if
if(llt(a,c)) then
print *, ''A is lexically less than B''
end if
end program testingChars
When you compile and execute the above program it produces the following result −
a is lexically greater than A B is lexically greater than A A is lexically less than a A is lexically less than B
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