---
title: "Partial CLS for the ZX81"
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slug: "partial-cls-for-the-zx81"
url: "http://localhost/article/partial-cls-for-the-zx81/"
markdown_url: "http://localhost/article/partial-cls-for-the-zx81.md"
published_at: "2025-07-28T01:17:02+00:00"
modified_at: "2025-07-28T01:17:03+00:00"
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excerpt: "Did you ever want to clear just the bottom portion of the screen during a BASIC program? Perhaps you have a title across the top line or two and would like for it to remain during the entire program. This little six byte machine code routine will allow just that. That's right SIX BYTES! Actually…"
category:
  - name: "The Data Expansion"
    slug: "the-data-expansion"
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  - name: "TS 1000"
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  - name: "Type-in program"
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model:
  - name: "Timex/Sinclair 1000"
    slug: "ts-1000"
    taxonomy: "model"
    url: "http://localhost/model/ts-1000/"
indiv:
  - name: "Jim Pitts"
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publication_r:
  id: 50143
  title: "The Data Expansion"
  type: "periodical"
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authors_r:
  - name: "Jim Pitts"
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volume: "5"
issue: "4"
issues_articles:
  - id: 50246
    title: "The Data Expansion v5 n4"
    type: "issue"
    url: "http://localhost/issue/the-data-expansion-v5-n4/"
pages: "16-17"
pubdate: "April 1988"
archive_link: false
---

# Partial CLS for the ZX81

Did you ever want to clear just the bottom portion of the screen during a BASIC program? Perhaps you have a title across the top line or two and would like for it to remain during the entire program. This little six byte machine code routine will allow just that. That’s right SIX BYTES! Actually the routine call a much longer routine in the ROM and passes on a single byte parameter which is first loaded into the B register.