19.2: Numeric to Character String Conversion

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An integer or real value can be converted into a character string using a write operation. The string is provided as the output variable instead of a file unit number. The numeric variable is provided as the input for the write operation.

The following is a simple example that will convert an integer into a string and a real into a string. Some numeric operations are performed on the numeric values and then the resulting strings are concatenated with another string. Concatenation can only be performed on character data types.

! Example program to use an internal write for
! character / numeric conversion.

program cvtExample2
implicit none
integer :: cvtErr
character(50) :: str1, str2, msg1, msg2
integer :: iNum=2468
real :: pi = 3.14, tau

    write (*,'(a, /)') "Example Conversion Program."

! ----------
!  Convert integer value to a string.

    iNum = iNum / 100
    write (str1, '(i3)', iostat=cvtErr) iNum
    
    if (cvtErr == 0 ) then
        msg1 = "My age is " // str1
        write (*,'(a, a)')                    &
            "Message 1 = ", msg1
    else
    
        write (*,'(a, /)') "Error, invalid conversion."      
    end if

! ----------
!  Convert real value to a string.

    tau = pi * 2.0
    write (str2, '(f5.3)', iostat=cvtErr) tau
    
    if (cvtErr == 0 ) then
        msg2 = "The value of TAU is " // str2
        write (*,'(a, a, /)')                 &
            "Message 2 = ", msg2
    else
        write (*,'(a, /)') "Error, invalid conversion."
    end if

end program cvtExample2

An example of the output for this program is as follows:

Example Conversion Program.

Message 1 = My age is 124
Message 2 = The value of TAU is 6.283

Once the numeric values are converted into strings, the character functions and character operations can be used as needed.