Errors

A failing word prints its message in red after a !, and the whole line is undone (transactions). Most messages are self-explanatory, and the others are described below.

Self-explanatory

division by zero, that list is empty, that position is outside the list, a [ is never closed, a string is never closed, there is a ] with no [ before it, there is a } with no { before it, { } needs names inside it, foo isn't defined, the stack is full, rand needs a number above 0, negative powers aren't supported, aleph needs 0 or more, card needs an ordinal, foo is already a unit, a unit name is 1 to 20 characters, a unit name uses lowercase letters, digits and -, there is no room for another unit, the tab number has to be 1 to 4, cr only takes 0, 2, 3 or 4, alloc takes 1 byte up to 16M, there is no such drive, that drive is too small, it needs at least 8M, cancelled, stopped, interrupted.

Explained

foo needs more values on the stack A value was consumed earlier or never pushed. 'foo help shows what the word expects.

times needs a number, and the same for other words Usually the arguments are in the wrong order, as in [ body ] 10 times instead of 10 [ body ] times.

+ needs numbers, len needs a string or a list, cat needs two strings or two lists A value of the wrong type. "5" 1 + fails where "5" >num 1 + works, and cat won't join a string to a list.

not a number: foo >num doesn't skip spaces.

map's quote has to leave exactly one value The quote left no value or more than one. Use filter to drop items.

too many local names More than 256 locals were live at once, almost always from recursion that binds locals at each level (flow).

this nests too deep Usually recursion that never reaches its base case.

foo isn't defined in this tab forget only removes your own tab's definitions (names).

there is no help for foo Your own words have no help entries (help).

foo needs a number that fits in 64 bits A bignum was passed to a word that needs a machine integer, such as times, at, peek or a bitwise word (numbers).

that number is too big, the limit is 2^65536 The result would have more than about 19,700 digits.

that number is too big to mix with an ordinal that way A bignum on the right of ordinal arithmetic, as in omega 2 100 ^ +. On the left it is absorbed, so 2 100 ^ omega + is omega.

that range is too big, that splits into too many parts, that quote is too long, the brackets are nested too deep A structure exceeded one of omega's limits.

that value can't go on the stack Ordinary omega code can't produce this error, so please report it.

ran out of memory The kernel heap is full (memory).

Infinity

ordinals only support + * and ^, cardinals only support + * and ^ Infinite values don't support subtraction or division (ordinals).

ordinals are never negative A negative integer in ordinal arithmetic, like omega -3 +.

can't mix cardinals with that, can't compare a cardinal with that Ordinals and cardinals can't be combined. Convert the ordinal with card first.

that cardinal power isn't supported, that exponent is too big to write out The result can't be computed or can't be represented.

ZFC can't decide this one (continuum hypothesis, Godel 1940 and Cohen 1963) The comparison depends on the continuum hypothesis, which is independent of ZFC (cardinals).

Root

foo isn't in any root unit open and src only work on root words. Use edit for tab definitions (root).

root unchanged, ... The edited unit failed to build, so root is unchanged and the edit was kept as a draft (root).

The JIT

foo can't be compiled, foo has no machine code The JIT can't compile the quote, or hasn't yet. Run it twice or use compile.

Disks

you haven't installed yet, run install save was used on the live ISO (installation).

the kernel doesn't fit in its slot, the kernel's data couldn't be copied These only happen with a much larger custom kernel (disk layout).

writing to the drive failed In QEMU this usually means a read-only image or a full disk on the host.

Faults

A CPU fault prints the fault, then your last line was dropped, and the tab restarts with its world intact (scheduler).