---
title: "Debugging Assembly with Hot Z-II"
type: "article"
slug: "debugging-assembly-with-hot-z-ii"
url: "http://localhost/article/debugging-assembly-with-hot-z-ii/"
markdown_url: "http://localhost/article/debugging-assembly-with-hot-z-ii.md"
published_at: "2026-01-12T15:39:34+00:00"
modified_at: "2026-01-12T15:40:04+00:00"
featured_image:
  url: "http://localhost/wp-content/uploads/2022/04/20230809-041332.jpg"
excerpt: "I recently started working on some assembly code that I had not touched in a long time. The assembled code (.p file) was working. I relooked at the code, re-assembled it and it failed to work. A cursory look at the code does not show the problem. As fast and small as assembly is, it…"
category:
  - name: "ZX26"
    slug: "zx26"
    taxonomy: "category"
    url: "http://localhost/category/periodicals/zx26/"
post_tag:
  - name: "TS 1000"
    slug: "ts1000"
    taxonomy: "post_tag"
    url: "http://localhost/tag/ts1000/"
  - name: "ZX81"
    slug: "zx81"
    taxonomy: "post_tag"
    url: "http://localhost/tag/zx81/"
model:
  - name: "Sinclair ZX81"
    slug: "zx81"
    taxonomy: "model"
    url: "http://localhost/model/zx81/"
  - name: "Timex/Sinclair 1000"
    slug: "ts-1000"
    taxonomy: "model"
    url: "http://localhost/model/ts-1000/"
indiv:
  - name: "Tim Swenson"
    slug: "tim-swenson"
    taxonomy: "indiv"
    url: "http://localhost/indiv/tim-swenson/"
publication_r:
  id: 62201
  title: "ZX-26"
  type: "periodical"
  url: "http://localhost/periodical/zx26/"
authors_r:
  - name: "Tim Swenson"
    slug: "tim-swenson"
    taxonomy: "indiv"
    url: "http://localhost/indiv/tim-swenson/"
issues_articles:
  - id: 62206
    title: "ZX-26"
    type: "issue"
    url: "http://localhost/issue/zx26/"
pages: "3-4"
pubdate: "January 2026"
product_reviews:
  - id: 12879
    title: "HOT Z-II"
    type: "product"
    url: "http://localhost/product/hot-z-ii/"
archive_link: false
---

# Debugging Assembly with Hot Z-II

I recently started working on some assembly code that I had not touched in a long time. The assembled code (.p file) was working. I relooked at the code, re-assembled it and it failed to work. A cursory look at the code does not show the problem.

As fast and small as assembly is, it can be difficult to troubleshoot. There is no easy way to add a print statement to output values. The disassembler in sz81 is helpful, but it goes too fast to see what is going on in the program. What I wanted was a tool that would let me step through the code, one line at a time, and see what is happening.

Luckily, [Hot Z-II](http://localhost/product/hot-z-ii/) has been preserved. Written by [Ray Kingsley](http://localhost/indiv/ray-kingsley/) in 1982, version 2 in available at the Internet Archive alone with the manual. I was able to download both and started reviewing the manual.