---
title: "ZX-FORTH"
id: 14717
type: "product"
slug: "zx-forth"
url: "http://localhost/product/zx-forth/"
markdown_url: "http://localhost/product/zx-forth.md"
published_at: "2019-11-30T01:18:26+00:00"
modified_at: "2026-03-22T13:39:33+00:00"
author: "David Anderson"
featured_image:
  url: "http://localhost/wp-content/uploads/2020/08/Gladstone-ZX-Forth.jpg"
excerpt: "Full implementation of FORTH for the ZX81/TS1000. Runs up to 10 times faster than Basic. ZX-FORTH complies with the FORTH-79 standard, with the exceptions of replacing the # sign with the British pound symbol, the @ sign with a question mark, the exclamation point with *, an apostrophe with the word \"tick\", and \"[\" and…"
category:
  - name: "Programming"
    slug: "programming"
    taxonomy: "category"
    url: "http://localhost/category/software/programming/"
post_tag:
  - name: "Artic Computing"
    slug: "artic-computing"
    taxonomy: "post_tag"
    url: "http://localhost/tag/artic-computing/"
  - name: "Downloadable"
    slug: "downloadable"
    taxonomy: "post_tag"
    url: "http://localhost/tag/downloadable/"
  - name: "Forth (programming language)"
    slug: "forth"
    taxonomy: "post_tag"
    url: "http://localhost/tag/forth/"
  - name: "Forth Dimension"
    slug: "forth-dimension"
    taxonomy: "post_tag"
    url: "http://localhost/tag/forth-dimension/"
  - name: "Gladstone Electronics"
    slug: "gladstone-electronics"
    taxonomy: "post_tag"
    url: "http://localhost/tag/gladstone-electronics/"
  - name: "International Publishing & Software Inc"
    slug: "international-publishing-software-inc"
    taxonomy: "post_tag"
    url: "http://localhost/tag/international-publishing-software-inc/"
  - name: "SofTek"
    slug: "softek"
    taxonomy: "post_tag"
    url: "http://localhost/tag/softek/"
  - name: "TS 1000"
    slug: "ts1000"
    taxonomy: "post_tag"
    url: "http://localhost/tag/ts1000/"
model:
  - name: "Timex/Sinclair 1000"
    slug: "ts-1000"
    taxonomy: "model"
    url: "http://localhost/model/ts-1000/"
genre:
  - name: "Programming"
    slug: "programming"
    taxonomy: "genre"
    url: "http://localhost/type/programming/"
  - name: "Software"
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    url: "http://localhost/type/software/"
company:
  id: 10657
  title: "Artic Computing"
  type: "company"
  url: "http://localhost/company/artic-computing/"
price: 29.95
date: 1982
rarity: "Uncommon"
related_content:
  - id: 36008
    title: "ZX Forth manual"
    type: "document"
    url: "http://localhost/document/zx-forth-manual/"
  - id: 35687
    title: "Gladstone Electronics February 1983 catalog"
    type: "document"
    url: "http://localhost/document/gladstone-electronics-february-1983-catalog/"
  - id: 19371
    title: "Gladstone Electronics Announces New Products"
    type: "article"
    url: "http://localhost/article/gladstone-electronics-announces-new-products/"
  - id: 25109
    title: "Go FORTH"
    type: "article"
    url: "http://localhost/article/go-forth/"
  - id: 24461
    title: "INTERP – The Kernel of Interactive Nuts"
    type: "article"
    url: "http://localhost/article/interp-the-kernel-of-interactive-nuts/"
  - id: 19989
    title: "New Product Announcement (Syntax v3 n6)"
    type: "article"
    url: "http://localhost/article/new-product-announcement/"
  - id: 19264
    title: "Putting Forth on ZX80/81s"
    type: "article"
    url: "http://localhost/article/putting-forth-on-zx80-81s/"
  - id: 40042
    title: "A Short Program in Forth (ZX Forth)"
    type: "article"
    url: "http://localhost/article/a-short-program-in-forth-zx-forth/"
  - id: 37997
    title: "Alternative Computer Languages for the ZX81: FORTH"
    type: "article"
    url: "http://localhost/article/alternative-computer-languages-for-the-zx81-forth/"
  - id: 22481
    title: "Review of ZX Forth from Gladstone"
    type: "article"
    url: "http://localhost/article/review-of-zx-forth-from-gladstone/"
  - id: 25709
    title: "To Buy or Not to Buy?"
    type: "article"
    url: "http://localhost/article/to-buy-or-not-to-buy/"
  - id: 16101
    title: "Unknown Tongues Alternative Computer Languages"
    type: "article"
    url: "http://localhost/article/unknown-tongues-alternative-computer-languages/"
related_products:
  - id: 51829
    title: "ZX-FORTH"
    type: "computer_media"
    url: "http://localhost/computer_media/zxforth/"
  - id: 56087
    title: "ZX Forth"
    type: "computer_media"
    url: "http://localhost/computer_media/zx-forth/"
companies_products:
  - id: 27015
    title: "Forth Dimension"
    type: "company"
    url: "http://localhost/company/forth-dimension/"
  - id: 10902
    title: "Gladstone Electronics"
    type: "company"
    url: "http://localhost/company/gladstone-electronics/"
  - id: 10960
    title: "International Publishing & Software Inc"
    type: "company"
    url: "http://localhost/company/international-publishing-software-inc/"
  - id: 11315
    title: "SofTek"
    type: "company"
    url: "http://localhost/company/softek/"
---

# ZX-FORTH

Full implementation of [FORTH](https://en.wikipedia.org/wiki/Forth_(programming_language)) for the ZX81/TS1000. Runs up to 10 times faster than Basic.

ZX-FORTH complies with the FORTH-79 standard, with the exceptions of replacing the # sign with the British pound symbol, the @ sign with a question mark, the exclamation point with *, an apostrophe with the word “tick”, and “[” and “]” with “(” and “)”. FORTH is unique in its ability to allow the programmer to build program solving modules then assign them user—defined names.

FORTH uses a stack for math, with a last-on/first-off structure, similar to [Reverse Polish notation](https://en.wikipedia.org/wiki/Reverse_Polish_notation). All arithmetic is integer and may use single or double precision and is faster than ZX/TS BASIC.

Conditional branching is supported and tests usually change the top number on the stack as a flag. ZX-FORTH supports ELSE for second level conditional execution.

User can exit to BASIC and return to ZX-FORTH through a USR call. ZX-FORTH retains all variables, constants, operators and the dictionary.

Though written for cassette storage, ZX-FORTH can be patched to support disks with routines less than 40 bytes long. Cassette load/save is faster than Sinclair BASIC.

ZX-FORTH comes with a [64 page manual](http://localhost/document/zx-forth-manual/) that include a bibliography of FORTH references. It has 6K of workspace when used with a 16K RAM pack. The size of the workspace can be increased with more memory.