feat(v4.0.0): the stacks are guarded (D-16); DEPTH, PICK and ROLL
Ruled 2026-10-04, revising D-2: stack overflow and underflow are errors that are shown and return to the prompt, not silent wrap-around. - Each stack counts what it holds. Before every opcode the executor checks that the stacks hold what it takes and have room for what it leaves; otherwise the opcode does nothing and the node faults, as for a bad address, to that kind's handler. Every fault empties both stacks. - The fault handler is now a table of five jumps: address, data overflow, data underflow, return overflow, return underflow. The host node says "Stack overflow", "Stack underflow", "Return stack overflow", "Return stack underflow", then ERROR and the prompt. - Two registers, DSTACK-DEPTH and RSTACK-DEPTH: a fetch reads the depth, a store empties the stack. QUIT, ABORT and the error exits empty the return stack before they call anything; ABORT empties the data stack. - capsule/forth.v4: DEPTH, PICK and ROLL, to FORTH-79 (counting from one). PICK and ROLL set the values above the one wanted aside in memory, and work with the stack full. - Division by zero now takes its operands off the stack, as v3 does. - A colon with no room for its entry abandons the line. - tests: every opcode at every depth of both stacks; the faults, the registers and the three words from the prompt. The sizes are unchanged: ten values, nine return entries. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
rajames
co-authored by
Claude Opus 5.5
Claude Opus 5.5
parent
361dcd1148
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0da7e32a0b
@@ -50,7 +50,7 @@ model produces the same results as the v3 C primitive it replaces.
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| Cell | 32 bits (mesh node). The host node's width is a build parameter; see D-5. |
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| Addressing | Word-addressed (D-1). |
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| Registers | `T` (top of data stack), `S` (second), `R` (top of return stack), `P` (program counter), `A` and `B` (address registers). |
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| Stacks | F18 circular hardware stacks, not visible to code (D-2): data stack `T`, `S` + 8 circular (10 deep), return stack `R` + 8 circular (9 deep). No overflow or underflow; pushing past the bottom silently overwrites the oldest entry. |
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| Stacks | F18 hardware stacks, not addressable by code: data stack `T`, `S` + 8 (10 deep), return stack `R` + 8 (9 deep). Each counts what it holds, and a push onto a full stack or a pop from an empty one is a **fault** (D-16, which replaces D-2's silent wrap-around). |
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| Instruction word | Six 5-bit slots, plus 2 spare bits. |
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### 1.2 Instruction word layout
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@@ -163,24 +163,26 @@ definition below depends on one, it says so.
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| ID | Decision | Ruling |
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| --- | --- | --- |
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| **D-1** | Word addressing (pure Moore) or byte addressing. | **Word addressing.** `C@`/`C!` are CAP; `CELLS` is a no-op. |
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| **D-2** | Stack depth, and whether the stacks are visible. | **F18 circular stacks, hidden.** Data stack 10 deep (`T`, `S` + 8 circular), return stack 9 deep (`R` + 8 circular), exactly as the F18. No stack pointer is visible to code, so `DEPTH`, `PICK`, `ROLL`, `.S`, `SP@` and `SP!` are **retired everywhere**, host node included. |
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| **D-2** | Stack depth, and whether the stacks are visible. | **F18 circular stacks, hidden.** Data stack 10 deep (`T`, `S` + 8 circular), return stack 9 deep (`R` + 8 circular), exactly as the F18. No stack pointer is visible to code, so `DEPTH`, `PICK`, `ROLL`, `.S`, `SP@` and `SP!` are **retired everywhere**, host node included. **Revised by D-16 (2026-10-04):** the sizes stand and the stacks are still not addressable, but they are no longer circular in effect — they are counted and guarded — and `DEPTH`, `PICK` and `ROLL` are back. |
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| **D-3** | Exact `+*` semantics at 32 bits: whether the add carries out of `T` into the shift. | **Plain F18 semantics.** The carry out of `T` is not kept. `UM*` in §4 is written for this and is exact over the full range (revised and proven on the golden model, 2026-10-02). |
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| **D-4** | Node memory map, including port and register addresses. | **Deferred** to step 2. Symbolic names only for now (§6, §7). |
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| **D-5** | Host node cell width. | **Match the host CPU:** 32 on a Zynq-7000 (Cortex-A9), 64 on an aarch64 host. The compiler capsule is written width-independent. |
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| **D-6** | Which heat structures exist in hardware: per-opcode counters only, or also per-call-target and word-to-word transition counters. | **Deferred** to step 2. The golden model implements per-opcode and per-call-target heat in the meantime. |
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| **D-7** | `ROLL` semantics. | **Moot.** `ROLL` is retired under D-2. |
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| **D-7** | `ROLL` semantics. | **FORTH-79** (2026-10-04, with D-16): `n ROLL` takes out the n-th value, counting from one and not counting `n`, and puts it on top; `3 ROLL` is `ROT`, `1 ROLL` does nothing; `n < 1` is an error. `PICK` counts the same way: `1 PICK` is `DUP`. v3's count from zero. |
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| **D-8** | Q48.16 signedness. | **Signed.** v3's unsigned comparisons and `Q.FROM-INT` clamping are retired. |
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| **D-9** | Instruction word width on a 64-bit-cell host (ruled 2026-10-02). | **32 bits at every cell width.** Six 5-bit slots plus 2 spare bits, as in §1.2. On a 64-bit host the instruction word is the low 32 bits of the cell and the high half is ignored, so compiled code is identical at both widths. Only data and `@p` literals are a full cell wide. |
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| **D-10** | Q48.16 width on a 64-bit-cell node (ruled 2026-10-02). | **Two cells at every cell width.** A Q value is a signed double on 32- and 64-bit nodes alike, so every Q word is the same double word at both widths. At 32-bit cells this is bit-for-bit v3's 64-bit Q. At 64-bit cells the low cell is v3's value, and where v3 wraps on Q48.16 overflow (a sum past Q max, `ABS` or `NEG` of Q min) the high cell carries the true result instead. |
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| **D-11** | `Q./` semantics: division by zero, rounding, overflow (ruled 2026-10-02). | **Saturate and flag; round toward zero; saturate on overflow.** The quotient of `a * 2^16 / b` is rounded toward zero, like `SM/REM`. When it does not fit a Q value it is clamped to Q max or Q min by its sign. Division by zero returns Q max or Q min by the sign of the dividend (`0 / 0` gives 0) and sets the node's `NODE-ERROR` register (§7), which `VM-ERROR?` reads. v3 returned 0 on division by zero and saturated whenever the dividend was 2^48 or more, even when the quotient would have fit. |
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| **D-12** | Q approximations outside their domain (ruled 2026-10-02). | **Return 0 and set `NODE-ERROR`.** `Q.SQRT` of a negative value and `Q.LOG` of zero or a negative value return 0 and set `NODE-ERROR` (§7), as `Q./` does on division by zero (D-11). v3 returned 0 for `ln(0)` without a flag and read negative arguments as large unsigned values. |
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| **D-13** | Pictured-output hold buffer: size and errors (ruled 2026-10-03). | **63 characters, as v3; on error set `NODE-ERROR` and drop the character.** The buffer holds 63 characters at either cell width. `HOLD` of a value outside 0–255, or into a full buffer, stores nothing and sets `NODE-ERROR` (§7), which is v3's behaviour (it set its error flag and dropped the character). A full double in base 2 therefore does not fit, as in v3. |
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| **D-14** | An address outside the node's memory (ruled 2026-10-04). | **Guarded: an address fault.** Every address a running programme uses is checked before it is used — `P` when an instruction word or an `@p` literal is fetched or `!p` stores, `A` for `@ @+ ! !+`, `B` for `@b !b`. Outside `0 … memory size − 1` the opcode does nothing (no fetch, no store, stacks and `A`, `B` untouched), the rest of its instruction word is not executed, and `P` becomes the node's **fault handler**. Nothing is pushed: the handler does not return to the programme. On the host node the handler is `(FAULT)` (`v4/capsule/quit.v4`): it prints `Address out of range`, ends any definition that was open, prints ` ERROR` and returns to the prompt, from however deep the fault was. A node with no handler stops. v3 printed ` ERROR` alone. What a mesh node's handler does — it has no console — comes with the mesh (step 2). Executed on the golden model (2026-10-04): `tests/test_exec.c` for every memory opcode and for `P`, `tests/test_host_quit.c` from the prompt. |
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| **D-15** | Division by zero in `/` `MOD` `/MOD` `*/` `*/MOD` `M/MOD` (ruled 2026-10-04). | **Guarded: the word reports it and the line ends.** Each of these words tests its divisor before anything else. If it is zero the word prints v3's message, its own name and `: Division by zero`, ends any definition that was open, prints ` ERROR` and returns to the prompt, from however deep; its caller is not returned to. `M/MOD` says so too, where v3 printed ` ERROR` alone. Source in `v4/capsule/forth.v4`; executed on the golden model's host node (2026-10-04), including transcripts of the v3 binary. `Q./` keeps D-11 (saturate and flag). `UM/MOD` and `SM/REM` are internal and unguarded: their callers have checked. What a mesh node, with no console, does on a zero divisor comes with the mesh (step 2); §4's definitions, which the mesh-node tests execute, still leave it unspecified. |
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| **D-14** | An address outside the node's memory (ruled 2026-10-04). | **Guarded: an address fault.** Every address a running programme uses is checked before it is used — `P` when an instruction word or an `@p` literal is fetched or `!p` stores, `A` for `@ @+ ! !+`, `B` for `@b !b`. Outside `0 … memory size − 1` the opcode does nothing (no fetch, no store, `A` and `B` untouched), the rest of its instruction word is not executed, both stacks are emptied (D-16), and `P` becomes the node's **fault handler** for that kind of fault. The handler does not return to the programme. On the host node the handler is `(FAULT)` (`v4/capsule/quit.v4`): it prints `Address out of range`, ends any definition that was open, prints ` ERROR` and returns to the prompt, from however deep the fault was. A node with no handler stops. v3 printed ` ERROR` alone. What a mesh node's handler does — it has no console — comes with the mesh (step 2). Executed on the golden model (2026-10-04): `tests/test_exec.c` for every memory opcode and for `P`, `tests/test_host_quit.c` from the prompt. |
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| **D-15** | Division by zero in `/` `MOD` `/MOD` `*/` `*/MOD` `M/MOD` (ruled 2026-10-04). | **Guarded: the word reports it and the line ends.** Each of these words tests its divisor before anything else. If it is zero the word prints v3's message, its own name and `: Division by zero`, takes its operands off the stack as v3 does, ends any definition that was open, prints ` ERROR` and returns to the prompt, from however deep; its caller is not returned to. `M/MOD` says so too, where v3 printed ` ERROR` alone. Source in `v4/capsule/forth.v4`; executed on the golden model's host node (2026-10-04), including transcripts of the v3 binary. `Q./` keeps D-11 (saturate and flag). `UM/MOD` and `SM/REM` are internal and unguarded: their callers have checked. What a mesh node, with no console, does on a zero divisor comes with the mesh (step 2); §4's definitions, which the mesh-node tests execute, still leave it unspecified. |
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| **D-16** | Stack overflow and underflow; `DEPTH`, `PICK`, `ROLL` (ruled 2026-10-04; revises D-2). | **Guarded: a stack fault.** Each stack counts what it holds. Before every opcode the node checks that the stacks hold what the opcode takes — including a `T` or `S` it only reads — and have room for what it leaves. If not, the opcode does nothing and the node faults exactly as for a bad address (D-14), to that kind's handler: `Stack overflow`, `Stack underflow`, `Return stack overflow`, `Return stack underflow`, then ` ERROR` and the prompt. **Every fault, D-14's included, empties both stacks**: the handler does not return, and what a word stopped part-way has left on the data stack is of no use to its caller. (v3 keeps what the failing word had not taken, and names the word: `DROP: Stack underflow`.) The fault handler is a table of five words, one per kind, each a jump (`(FAULTS)` in `v4/capsule/quit.v4`). Two registers (§7) are all a programme sees of the stacks: `DSTACK-DEPTH` and `RSTACK-DEPTH` read as the depth, and a store to one empties that stack. There is still no stack pointer and no address for a stack cell, so `SP@` and `SP!` stay retired; `.S` waits for number output to reach the capsule. The sizes are unchanged, 10 and 9: one more value, or one more level of call, is now an error message where it used to be silent corruption. Executed on the golden model (2026-10-04): `tests/test_exec.c` for every opcode at every depth of both stacks, `tests/test_host_quit.c` from the prompt. |
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**Consequences of D-2 that every definition must respect.** The data stack holds 10 items and the
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return stack 9, and every `call`, `FOR`, `DO` loop frame and `push` uses return-stack slots. Nesting
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is therefore shallow, and exceeding either depth corrupts silently rather than faulting. Every CAP
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is therefore shallow, and exceeding either depth is a stack fault (D-16; before 2026-10-04 it
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corrupted silently). Every CAP
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definition in §4 and §5 must be re-checked against these limits before it is accepted as a POST
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target; the hand traces so far assumed unbounded stacks.
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@@ -311,9 +313,9 @@ Section numbers match the v3 primitive reference.
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| `?DUP` | CAP | `if Z dup ; Z: ;` (`dup IF dup THEN` without the extra copy). Executed on the golden model (2026-10-03), including a transcript of the v3 binary. |
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| `ROT` | CAP | §4. Executed on the golden model (2026-10-03), including a transcript of the v3 binary. Leaves its caller 6 data cells and 4 return entries; in line, with `SWAP` in line, it calls nothing. |
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| `-ROT` | CAP | `SWAP push SWAP pop`, `SWAP` in line (`ROT ROT` in one pass). Executed on the golden model (2026-10-03), including a transcript of the v3 binary. Leaves its caller 6 data cells and 5 return entries. |
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| `DEPTH` | RET | No visible stack pointer (D-2). |
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| `PICK` | RET | No visible stack pointer (D-2). |
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| `ROLL` | RET | No visible stack pointer (D-2); D-7 is moot. |
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| `DEPTH` | CAP | FORTH-79: how many values were on the stack before `DEPTH`. `DSTACK-DEPTH b! @b` (D-16). Source in `v4/capsule/forth.v4`; executed on the golden model's host node (2026-10-04), including a transcript of the v3 binary. |
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| `PICK` | CAP | FORTH-79 (D-7): `( n -- x )`, a copy of the n-th value counting from one; `1 PICK` is `DUP`, `2 PICK` is `OVER`. The stack has no addresses, so the `n - 1` values above the one wanted are set aside in memory and put back. `n < 1` prints `PICK: Invalid index`; `n` greater than the depth is a stack underflow fault. It works with the stack full (nine values and `n`). v3's `PICK` counts from zero. Source in `v4/capsule/forth.v4`; executed on the golden model's host node (2026-10-04). |
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| `ROLL` | CAP | FORTH-79 (D-7): `( n -- )`, the n-th value counting from one is taken out and put on top; `3 ROLL` is `ROT`, `1 ROLL` does nothing. Built as `PICK` is, with the same errors. v3's `ROLL` counts from zero. Source in `v4/capsule/forth.v4`; executed on the golden model's host node (2026-10-04). |
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### 5.2 Return stack
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@@ -469,7 +471,7 @@ All output reaches the console through `EMIT` (DEV).
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| `HLD` | CAP | Variable: byte address of the first held character. `HLD ( -- addr )` is the variable's word address, a literal. Not a v3 word. Executed on the golden model (2026-10-03): after `<#` and each `HOLD` or `#`, `HLD @` is the address `#>` returns. |
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| `.` `.R` `U.` `U.R` `D.` `D.R` | CAP | Built on pictured output and `TYPE`; definitions below. `.`, `U.` and `D.` print the number in the current base, then one space. The `.R` words right-justify it in `width` columns, print a wider number whole, pad nothing for `width <= 0`, and print no space after it: that is FORTH-79's reference word (ruled 2026-10-04); v3 printed a space after these too. Where v4 parts from v3: a double is `( lo hi )`, where v3's `D.` took the low cell on top; `D.` prints the whole double, where v3 printed `DOUBLE-OVERFLOW` unless it fitted one signed cell (they agree whenever it does); printing honours the `BASE` variable, where v3 printed in a host copy that only `DECIMAL`, `HEX` and `OCTAL` set, so `n BASE !` changed v3's input base but not its output; and the number is built in the 63-character hold buffer, so a longer one — a 64-bit cell in base 2, a large double in a small base — loses its leading characters and sets `NODE-ERROR` (D-13), where v3 printed from a private 80-character buffer. Executed on the golden model (2026-10-03) against a C reference in the ten bases of the pictured-output test and eleven field widths, and against five transcripts of the v3 binary (a sixth, the extreme cells, at 64-bit cells). Each leaves its caller 4 data cells; `U.` and `U.R` leave 3 return entries, the signed words 2, their sign waiting on the return stack. All clobber `A` and `B`. |
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| `(W)` | CAP | Variable, 2 cells: the field width of the `.R` words, and whether a blank follows the number. Like `BASE` and `HLD`, it lives in node memory, so the width is on neither stack while the picture runs. |
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| `.S` | RET | No visible stack pointer (D-2). |
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| `.S` | CC | Possible again under D-16 (`DEPTH` and `PICK`); not written until number output is in the capsule. |
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| `?` | CAP | `( addr -- )`: `a! @ jump .` — the cell at word address `addr` (D-1), printed as `.` prints it. Executed on the golden model (2026-10-03), including a transcript of the v3 binary. Leaves its caller 4 data cells and 2 return entries. Clobbers `A` and `B`. |
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| `DUMP` | CAP | `( baddr u -- )`: `u` bytes from byte address `baddr`, sixteen to a line, in v3's format: the address in hex, `": "`, each byte as two hex digits and a space (three spaces where the line runs out), `" \|"`, the bytes as characters with `.` for anything outside 32–126, `"\|"` and a new line. Always hex, whatever `BASE` is, and `BASE` is put back. The address is two hex digits per byte of a cell — 8 at 32-bit cells, 16 at 64, which is v3's width. Nothing for `u = 0`; for `u < 0` nothing is printed and `NODE-ERROR` is set, as `TYPE` does, where v3 raised its error flag. Addresses are not range-checked (open, `node.h`). Definition below. Executed on the golden model (2026-10-03) against a C reference at six alignments and every length 0–50, and at 64-bit cells against a transcript of the v3 binary, byte for byte. Leaves its caller 4 data cells and 4 return entries. Clobbers `A` and `B`. |
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| `(DP)` | CAP | Variable, 4 cells: `DUMP`'s saved `BASE`, address, count and column. |
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@@ -677,7 +679,7 @@ The storage service belongs to the Artemis role, now a device node.
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| Word | Fate | Notes |
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| --- | --- | --- |
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| `HERE` `ALIGN` `ALLOT` `,` `C,` `2,` `PAD` `LATEST` | CC | The dictionary lives on the host node; source in `v4/capsule/dict.v4`. The dictionary pointer `DP` is a byte address, so `C,` packs four characters to a cell; `HERE` is the next whole cell (a word address); `,` and `ALLOT` align first. An address unit is a cell (D-1), so `ALLOT` counts cells where v3's counted bytes; a negative count gives space back. `2,` stores the low cell first, as v3. Going outside the dictionary space stores nothing, moves nothing and sets `NODE-ERROR`. `PAD` is a fixed scratch area, as in v3, given as a byte address. `LATEST` is the xt of the newest entry, 0 if there is none (v3's pushes `HERE`, which looks like a bug; reported, not changed). Executed on the golden model's host node (2026-10-04). `,` calls nothing and leaves its caller 7 data cells and 8 return entries; `ALLOT` leaves 7 and 7. |
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| `SP@` `SP!` | RET | No visible stack pointer (D-2). |
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| `SP@` `SP!` | RET | A stack cell has no address (D-2, D-16). `DEPTH`, and a store to `DSTACK-DEPTH` to empty the stack, are what remain of them. |
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### 5.13 Dictionary manipulation
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@@ -717,8 +719,8 @@ it, `xt + 1`; for any other word the parameter field is the code itself.
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| `(` `\` | CC | `(` is `41 WORD drop`; `\` is `SPAN @ >IN !`. In `v4/capsule/input.v4` under the names `PAREN` and `BACKSLASH`. Executed on the golden model's host node (2026-10-04). |
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| `EXECUTE` | CAP | `push ;` (tail-jumps to the xt; the xt returns to `EXECUTE`'s caller). Executed on the golden model's host node (2026-10-04). |
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| `NOP` | OP | `nop` |
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| `QUIT` | CC | FORTH-79; source in `v4/capsule/quit.v4`. Clears the return stack, sets execution mode, returns control to the terminal; no message. It is the prompt: after a new line it prints `ok> `, reads a line with `QUERY`, clears `NODE-ERROR`, runs `INTERPRET`, prints ` ok` — or, if `NODE-ERROR` is set, ends any definition that was open and prints ` ERROR` — and goes round again, for as long as the node runs. The text is v3's. The line is not sent back; the terminal shows what is typed. The return stack is circular (D-2) and has no bottom to reset to: `QUIT` clears it by jumping into the loop and never returning, from however deep. The data stack is left alone. A definition open when `QUIT` runs is ended and stays hidden. Executed on the golden model's host node (2026-10-04): the node is started at `QUIT`, fed characters and its output read, including 16 sessions recorded from the v3 binary. v3's `QUIT` goes on with the rest of the line and cannot be compiled into a definition. |
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| `ABORT` | CC | FORTH-79; source in `v4/capsule/quit.v4`. As `QUIT`, and the line it stops ends with ` ok`, as v3. The data stack is circular (D-2): there is nothing to clear, and what was on it is still there. Executed on the golden model's host node (2026-10-04), from six calls down and from inside two loops, forty times over. |
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| `QUIT` | CC | FORTH-79; source in `v4/capsule/quit.v4`. Clears the return stack, sets execution mode, returns control to the terminal; no message. It is the prompt: after a new line it prints `ok> `, reads a line with `QUERY`, clears `NODE-ERROR`, runs `INTERPRET`, prints ` ok` — or, if `NODE-ERROR` is set, ends any definition that was open and prints ` ERROR` — and goes round again, for as long as the node runs. The text is v3's. The line is not sent back; the terminal shows what is typed. It empties the return stack first, by a store to `RSTACK-DEPTH` (D-16), so it works from however deep, with the return stack full. The data stack is left alone. A definition open when `QUIT` runs is ended and stays hidden. Executed on the golden model's host node (2026-10-04): the node is started at `QUIT`, fed characters and its output read, including 16 sessions recorded from the v3 binary. v3's `QUIT` goes on with the rest of the line and cannot be compiled into a definition. |
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| `ABORT` | CC | FORTH-79; source in `v4/capsule/quit.v4`. As `QUIT`, and it empties the data stack too (a store to `DSTACK-DEPTH`, D-16); the line it stops ends with ` ok`, as v3. Executed on the golden model's host node (2026-10-04), from six calls down and from inside two loops, forty times over, including transcripts of the v3 binary. |
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| `ABORT"` `(ABORT")` | CC | Not FORTH-79 (it is FORTH-83's); kept because v3 has it. `ABORT" text"` `( flag -- )`: if the flag is not zero, print the text, start a new line and `ABORT`. Compiled as `."` is, with `(ABORT")` as the run-time word; it also works at the prompt. Executed on the golden model's host node (2026-10-04). v3's crashes (SIGSEGV) when a word compiled with it runs, and at the prompt prints the text and carries on with the line. |
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| `COLD` `WARM` | CC | |
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| `BYE` `REBOOT` | HERA | |
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@@ -751,7 +753,7 @@ call would bury what it works on. A **compile-only** word may not be executed by
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`v4/capsule/forth.v4` holds the first words of the vocabulary flagged this way (`DUP`, `+`, `>R`, `I`,
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`LEAVE`, `@`, the in-line variables and so on).
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**The short stacks (D-2) and the compiler.** The interpreter and compiler run on the same ten-cell and
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**The short stacks (D-2, D-16) and the compiler.** The interpreter and compiler run on the same ten-cell and
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nine-entry stacks as the user's words, with the user's values beneath them. Two consequences are
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built into the capsule:
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@@ -1044,3 +1046,5 @@ Addresses are assigned in the node memory map (D-4). Names only here.
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| `CONSOLE-TX` | W | Console transmit: a store sends the low 8 bits of the value as one character. This is what `EMIT` writes to. On the single-node golden model it is a capture register: the character is appended to a buffer on the node and memory is not written (`v4_node_console_attach`, `v4/include/v4/node.h`), so printing words can be run and their output compared with v3's. With the mesh (step 2) it becomes the port to the console node. |
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| `CONSOLE-RX` | R | Console receive: a fetch gives the next pending character, 0–255, and takes it; with none pending it gives −1 and takes nothing. This is what `KEY` reads. On the single-node golden model the characters come from a queue the test feeds (`v4_node_console_input_attach`, `v4_node_console_feed`, `v4/include/v4/node.h`). Only the data fetches `@`, `@+` and `@b` see the register; instruction words and literals at the same address are read as memory. With the mesh (step 2) it becomes the port from the console node, and a read with nothing pending will block instead. |
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| `CONSOLE-STATUS` | R | Console receive status: a fetch gives −1 when a character is pending and 0 when not, and changes nothing. `?TERMINAL` reads it, and `KEY` polls it. On the mesh it is the console port's bit of `PORT-STATUS`. |
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| `DSTACK-DEPTH` | R/W | A fetch gives how many values the data stack holds, the fetch's own push not counted. A store empties the data stack; the value stored is taken off first and ignored. `DEPTH` reads it; `ABORT` stores to it (D-16). |
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| `RSTACK-DEPTH` | R/W | The same for the return stack. `QUIT`, `ABORT` and the error exits store to it before they call anything. |
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Reference in New Issue
Block a user