OCTVAL(string-expression)

Returns the integer value of a string containing an octal number. The string must consist only of valid octal digits (0–7).

PRINT OCTVAL("10")

Produces 8.

PRINT OCTVAL("755")

Produces 493.

REM Convert user input
INPUT "Enter an octal number > " ; o$
val = OCTVAL(o$)
PRINT "You entered decimal "; val

REM Round-trip using OCT$
n = 64
o$ = OCT$(n)
PRINT o$; " = "; OCTVAL(o$)

Parsing is strict: only digits 0–7 are allowed.
Returns a 64-bit integer.
If the string is empty, or contains any character outside 0–7, the return value is 0.
Important distinction:
- In BASIC source code, you can write octal literals with a &O prefix (e.g. &O755).
- In strings passed to OCTVAL, only the raw digits are valid — no prefix.

See also: OCT$ · STR$ · HEXVAL