TEXTIO Procedures

TEXTIO defines a LINE data type
- All read and write operations use the LINE type
TEXTIO also defines a FILE type of TEXT for use with ASCII text
Procedures defined by TEXTIO are:
- READLINE(f, k)
  - reads a line of file f and places it in buffer k
- READ(k, v,...)
  - reads a value of v of its type from k
- WRITE(k, v,...)
  - writes value v to LINE k
- WRITELINE(f, k)
  - writes k to file f
- ENDFILE(f) returns TRUE at the end of FILE