Tandy 1000 Basic Reference Manual

Chapter 10 I BASIC Keywords
Example
10 COM(1) ON
200 ON COM(1 1 GOSUB 1000
Line 10 turns on communication trapping on Channel 1. After
each program statement is executed, BASIC checks
to see if the
communication buffer contains characters. If it does, BASIC im-
mediately executes the subroutine beginning at Line 1000.
10 COM(1) ON
20 ON COMC1) GOSUB 1000
30 FOR I = 1 TO 10
40 PRINT I
50 NEXT I
1000 ’ SUBROUTINE CODE
1050 RETURN 200
If activity occurs on Communication Channel 1 while the FOR/
NEXT loop
is executing, BASIC immediately executes the sub-
routine beginning
at Line 1000. But the subroutine returns to
Line 200 instead of completing the FORiNEXT loop. This results
in a “For without next” error because any GOSUB, FOR,
or
WHILE statement remains active during key trapping.
If the RETURN statement does not include a line number, pro-
gram control returns to complete the FOR/NEXT loop, and no
error occurs.
227

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