Tandy 1000 Basic Reference Manual

Chapter 10 I BASIC Keywords
LOF
Function
LOF ( buffer)
Returns the length of the file in bytes.
Buffer is the number assigned to the file when you opened it.
Example
Y = LOF(5)
assigns the length of the file in bytes to variable Y
Sample Programs
During direct access to an existing file, you often need a way to
know when you have read the last valid record.
LOF provides a
way:
1540 OPEN "R", 1, "unknown.txt", 128
1550 FIELD 1, 128 AS A$
1560 RCNUM% = 1 'START AT BEGINNING OF FILE
1570 RCSIZ% = 128 'SET RECORD SIZE
1580 IF RCNUM% * RCSIZ% > LOF(1) GOTO 1640
1590 'CHECK FOR END OF FILE
1600 GET 1, RCNUMX 'RECORD NUM. TO BE ACCESSED
1610 PRINT AS
1620 RCNUM% = RCNUM% + 1 'INCREMENT RECORD NUM
1630 GOTO 1580
1640 CLOSE
If you attempt to GET record numbers beyond the end-of-file,
BASIC gives you an error.
These lines use
LOF to determine where to start adding when
you want to add to the end of
a file:
1700 RCNUM% = (LOFC1) / RCSIZ%) + 1
1720 'HIGHEST EXISTING RECORD
1720 PUT 1, RCNUM% 'ADD NEXT RECORD
210

Tandy 1000 Specifications

General

Processor	Intel 8088
Processor Speed	4.77 MHz
RAM	128 KB (expandable to 640 KB)
Operating System	MS-DOS 2.11
Manufacturer	Tandy Corporation
Release Year	1984
Storage	Single or double 5.25" floppy disk drive (360 KB), optional hard drive
Sound	Tandy 3-voice sound
Ports	Parallel, Serial
Graphics	CGA (Color Graphics Adapter)
Graphics Modes	320x200, 640x200