DOS 3.3: Commands ignored

The CTRL-D of a DOS command must be the first character on an output line and must immediately follow a carriage return. If it doesn't, the command is printed on the screen or to the printer, but is ignored by DOS.
GET or PRINT statements that end with one of the following often cause this problem:
A PRINT statement on the line above a DOS command generates the necessary carriage return; alternatively, define D$ as a carriage return and a CTRL-D:

10 D$ = chr$ (13) + chr$ (4)

DOS commands are also ignored when improperly used. IN# and PR# DOS commands, for example, must be sent out as:

10 print chr$(4);"IN#0"
20 print chr$(4);"PR#0"

For further explanation, refer to pages 100 through 103 of The DOS Manual or page 25 of The DOS Programmer's Manual.
Published Date: Feb 18, 2012