---
title: "QL System Variables"
type: "article"
slug: "ql-system-variables"
url: "http://localhost/article/ql-system-variables/"
markdown_url: "http://localhost/article/ql-system-variables.md"
published_at: "2026-03-15T00:41:31+00:00"
modified_at: "2026-03-15T00:41:32+00:00"
featured_image:
  url: "http://localhost/wp-content/uploads/2022/04/20230809-041332.jpg"
excerpt: "Reference guide to selected Sinclair QL system variables with addresses, sizes, and usage notes. Covers RAMTOP+1 (memory expansion detection at 163950), SCREEN_CTD (TV mode status at 163990), SCREEN_STATUS (screen activity at 163991), NET# (network number at 163995), REPEAT_DELAY (163986 word), REPEAT_FREQ (163952 word), and CAPS_LOCK (163976 word, noting a correction to a previous TimeLinez article).…"
category:
  - name: "Timelinez"
    slug: "timelinez"
    taxonomy: "category"
    url: "http://localhost/category/periodicals/timelinez/"
post_tag:
  - name: "QL"
    slug: "ql"
    taxonomy: "post_tag"
    url: "http://localhost/tag/ql/"
  - name: "Superbasic (programming language)"
    slug: "superbasic-programming-language"
    taxonomy: "post_tag"
    url: "http://localhost/tag/superbasic-programming-language/"
model:
  - name: "Sinclair QL"
    slug: "sinclair-ql"
    taxonomy: "model"
    url: "http://localhost/model/sinclair-ql/"
indiv:
  - name: "Tim Swenson"
    slug: "tim-swenson"
    taxonomy: "indiv"
    url: "http://localhost/indiv/tim-swenson/"
publication_r:
  id: 21571
  title: "Timelinez"
  type: "periodical"
  url: "http://localhost/periodical/timelinez/"
authors_r:
  - name: "Tim Swenson"
    slug: "tim-swenson"
    taxonomy: "indiv"
    url: "http://localhost/indiv/tim-swenson/"
volume: "7"
issue: "12"
issues_articles:
  - id: 38873
    title: "Timelinez v7 n7-12"
    type: "issue"
    url: "http://localhost/issue/timelinez-v7-n7-12/"
pages: "8"
pubdate: "July-December 1989"
archive_link: false
---

Reference guide to selected Sinclair QL system variables with addresses, sizes, and usage notes. Covers RAMTOP+1 (memory expansion detection at 163950), SCREEN_CTD (TV mode status at 163990), SCREEN_STATUS (screen activity at 163991), NET# (network number at 163995), REPEAT_DELAY (163986 word), REPEAT_FREQ (163952 word), and CAPS_LOCK (163976 word, noting a correction to a previous TimeLinez article). Also explains POKE_L/PEEK_L, POKE_W/PEEK_W, and POKE/PEEK usage, and provides the formula for calculating free memory: PEEK_L(163985) – PEEK_L(163965) – 5168.