TOPS-20 PASCAL Language Manual - Bitsavers

INPUT AND OUTPUT
• PASCAL input and output procedures
• Terminal 1/0
The input and output procedures are presente~
in alphabetical order.
7.1 FILE CHARACTERISTICS
This section describes the organization of records and methods of
accessing records.
The term file organization app] ies to the way records are physically
arranged on a storage device. The term record cccess refers to the
method used to read records from or write records to a file,
regardless of the file's organization. A file's organization is
specified when the file is created and cannot be changed. Record
access is specified each time the file is opened and can vary.
7.1.1 File Names
The file name indicates the system name of a file that is represented
by a PASCAL file variable in an OPEN procedure (Section 7.7). For the
file name, you can specify a character-string expression that contains
a TOPS-20 file specification or a logical name. Apostrophes are
required to delimit a character-string constant or a logical name used
as a file name.
7.1.2 Logical Names
The TOPS-20 operating system provides the logical name mechanism as a
way of making programs device and file independent. If you use
logical names, your PASCAL program need not specify the particular
device on which a file resides or the particular file that contains
data. Specific devices and files can be defined at run time.
A logical name is an alphanumeric string that you specify in place of
a file specification. Logical names provide great flexibility because
they can be associated not only with. a complete file specification,
but also with a device, a device and a directory, or even another
logical name.
On TOPS-20 you can create a logical name and associate it with a file
specification by means of the TOPS-20 DEFINE command. Thus, before
program execution, you can associate the logical names in your program
with the file specifications appropriate to your needs, for example:
@DEFINE DATA:
PS: