LOC

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 #

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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

• PRINT, OPEN COM, PRINT (file statement)
• SEEK, SEEK (function)

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