---
title: "Examining Machine Code"
id: 76428
type: "computer_media"
slug: "examining-machine-code"
url: "http://localhost/computer_media/examining-machine-code/"
markdown_url: "http://localhost/computer_media/examining-machine-code.md"
published_at: "2026-11-11T08:02:43+00:00"
modified_at: "2026-11-11T08:02:43+00:00"
author: "David Anderson"
featured_image:
  url: "http://localhost/wp-content/uploads/2026/11/examining-machine-code-1.png"
excerpt: "Look at memory one address at a time and change bytes as you go, in decimal or, with the alternative lines, in hex."
post_tag:
  - name: "Downloadable"
    slug: "downloadable"
    taxonomy: "post_tag"
    url: "http://localhost/tag/downloadable/"
  - 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: "Nels Anderson"
    slug: "anderson-nels"
    taxonomy: "indiv"
    url: "http://localhost/indiv/anderson-nels/"
genre:
  - name: "Machine Language"
    slug: "machine-language"
    taxonomy: "genre"
    url: "http://localhost/type/machine-language/"
media_type: "Program"
programmers:
  - name: "Nels Anderson"
    slug: "anderson-nels"
    taxonomy: "indiv"
    url: "http://localhost/indiv/anderson-nels/"
download_url: "https://archive.org/download/timex-sinclair-software-archive/Examining%20Machine%20Code%20%281983%29%28Anderson%2C%20Nels%29%28TS1000%29%28US%29%28Program%29.zip"
mediadate: "1983"
images:
  - url: "http://localhost/wp-content/uploads/2026/11/examining-machine-code-1.png"
  - url: "http://localhost/wp-content/uploads/2026/11/examining-machine-code-2.png"
article_media:
  - id: 19575
    title: "Examining Machine Code"
    type: "article"
    url: "http://localhost/article/examining-machine-code/"
media_type_tags: "Machine Language"
license: false
---

# Examining Machine Code

A small memory editor for checking and changing machine code. Add it to the end of a program and GOTO 9500, or RUN it on its own. Give a starting address, and the program shows the address and its contents. Type a new value of up to three digits to POKE it (ENTER after fewer than three), ENTER to leave it alone, or / to go back to the previous address. Because it reads keys with INKEY$, use it in SLOW mode. BREAK stops it.

The second listing replaces three lines to show and enter the bytes as two-digit hex numbers. The download has both versions.

Published in Syntax December 1983 ([Examining Machine Code](https://timexsinclair.com/article/examining-machine-code/)).

## Source Code

```
9500 PRINT "ADDRESS"
9510 INPUT ADR
9515 SCROLL
9520 PRINT ADR;" ";PEEK ADR;"   ";
9525 LET NEW=0
9530 FOR I=1 TO 3
9535 IF INKEY$<>"" THEN GOTO 9535
9536 IF INKEY$="" THEN GOTO 9536
9540 LET X$=INKEY$
9550 IF X$=CHR$ 118 AND I=1 THEN GOTO 9610
9560 IF X$=CHR$ 118 THEN GOTO 9600
9565 IF X$="/" THEN GOTO 9640
9566 PRINT X$;
9570 LET NEW=NEW*10+VAL X$
9580 NEXT I
9600 POKE ADR,NEW
9610 SCROLL
9620 LET ADR=ADR+1
9630 GOTO 9520
9640 SCROLL
9650 LET ADR=ADR-1
9960 GOTO 9520

9520 PRINT ADR;" ";CHR$ (INT ((PEEK ADR)/16+28));CHR$ ((PEEK ADR)-16*INT ((PEEK ADR)/16)+28);" -";
9530 FOR I=1 TO 2
9570 LET NEW=NEW*16+CODE X$-28
```