A function which returns the length of the argument string.
X=LEN"fred" X=LENA$ X=LEN(A$+B$)
This function 'counts' the number of characters in a string. For example,
would set 'length' to 16 since the string consists of the 13 characters of BBCBASIC(Z80) followed by three spaces.
LEN is often used with a FOR...NEXT loop to 'work down' a string doing something with each letter in the string. For example, the following program looks at each character in a string and checks that it is a valid hexadecimal numeric character.
10 valid$="0123456789ABCDEF" 20 REPEAT 30 INPUT "Type in a HEX number" hex$ 40 flag=TRUE 50 FOR i=1 TO LEN(hex$) 60 IF INSTR(valid$,MID$(hex$,i,1))=0 flag=FALSE 80 NEXT 90 IF NOT flag THEN PRINT "Bad HEX" 100 UNTIL flag