LOC
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The LOC function returns the status of a serial (COM) port received buffer or the last read/written byte or record position in an open file.
Syntax
- bytes% = LOC(fileOrPortNumber%)
Parameters
- fileOrPortNumber% is the number used in the port or file OPEN AS statement.
- Returns 0 if the buffer is empty. Any value above 0 indicates the COM port has received data.
- Use it in conjunction with INPUT$ to get the data bytes received.
- Can also be used to get the last read/written byte or record position in a file. See also SEEK.
Notes
- Don't confuse the LOC position with the SEEK position !!
- LOC is the last read or written byte or record prosition.
- SEEK is the byte or record prosition to read or write next.
Examples
- Example 1
- Reading and writing from a COM port opened in Basic.
OPEN "COM1: 9600,N,8,1,OP0" FOR RANDOM AS #1 LEN = 2048 ' random mode = input and output DO: t$ = INKEY$ ' get any transmit keypresses from user IF LEN(t$) THEN PRINT #1, t$ ' send keyboard byte to transmit buffer bytes% = LOC(1) ' bytes in buffer IF bytes% THEN ' check receive buffer for data" r$ = INPUT$(bytes%, 1) ' get bytes in the receive buffer PRINT r$; ' print byte strings consecutively to screen" END IF LOOP UNTIL t$ = CHR$(27) 'escape key exit CLOSE # |
- Example 2
- Demonstrate the difference between LOC and SEEK positions in a file.
OPEN "readme.md" FOR BINARY AS #1 PRINT LOC(1) 'LOC returns 0, as we didn't read something yet PRINT SEEK(1) 'SEEK otherwise returns 1, as it's the first byte to read GET #1, , a& 'now let's read a LONG (4 bytes) PRINT LOC(1) 'now LOC returns 4, the last read byte PRINT SEEK(1) 'and SEEK returns 5 now, the next byte to read CLOSE #1 END |
0 1 4 5 |
See also