The (TM) control code places a transmit mark character at the current cursor position. The transmit mark is automatically displayed in suppressed background (invisible) mode and occupies one space on the video screen.
When the Tab, Return, or Enter key is pressed and the cursor advances past a transmit mark, the video device transmits to the host computer all foreground data between the last transmit mark and the previous transmit mark on the screen.
Thus, transmit marks form delimiters for block data transmission. One transmit mark should be placed at the beginning of the data block to be sent to the host computer, and another transmit mark should be placed at the end of the data block. Cursor movement between the two transmit marks does not result in data transmission to the host system. Only when the ending transmit mark is crossed is the data block sent to the host system.
This control code may also include a positioning statement to place a transmit mark at a specific point on the screen.
See Transmit Stop (TP).
100 FORMAT (CS);_ ! clear screen
(EN);_ ! enter normal mode
(SB);_ ! start background
"CUSTOMER NUMBER:",@(0,5);_ ! prompt
(TM);_ ! transmit mark
(SF);" ";_ ! foreground spaces
(TM);_ ! transmit mark
@17,5) ! move cursor
.
.
.
PRINT (0,100)
INPUT (0) CUSTNUM$
This example combines several video control codes to demonstrate
the basic function of the transmit mark. The
FORMAT statement
starts by clearing the screen (using the
(CS) control code) and
entering normal mode (using the
(EN) control code).
Then, the (SB) control code is used to start background display mode. A prompt is displayed starting at column 0, row 5. Following the prompt, a transmit mark is displayed.
Next, the (SF) control code is used to start foreground display mode (for a data entry field), and five blank spaces are displayed. Following these spaces, another transmit mark is displayed.
The final element in the FORMAT statement moves the cursor to column 17, row 5, which is the left-most character in the data entry field. This data entry field is made up of five foreground blanks surrounded by transmit marks. When the second transmit mark is crossed by an operator action or forced transmit from the program itself, the data in the data entry field will be sent to the host computer.