---
title: "Color Show"
id: 71185
type: "computer_media"
slug: "color-show"
url: "http://localhost/computer_media/color-show/"
markdown_url: "http://localhost/computer_media/color-show.md"
published_at: "2026-08-30T22:48:03+00:00"
modified_at: "2026-08-30T22:48:04+00:00"
author: "David Anderson"
featured_image:
  url: "http://localhost/wp-content/uploads/2022/04/20230809-041332.jpg"
excerpt: "A hypnotic random walk paints colored blocks across the screen, drifting through nine paper colors with every unpredictable step."
category:
  - name: "Archived Media"
    slug: "archived-media"
    taxonomy: "category"
    url: "http://localhost/category/archived-media/"
post_tag:
  - name: "Downloadable"
    slug: "downloadable"
    taxonomy: "post_tag"
    url: "http://localhost/tag/downloadable/"
  - name: "TS 2068"
    slug: "ts2068"
    taxonomy: "post_tag"
    url: "http://localhost/tag/ts2068/"
model:
  - name: "Timex/Sinclair 2068"
    slug: "ts-2068"
    taxonomy: "model"
    url: "http://localhost/model/ts-2068/"
genre:
  - name: "Demo"
    slug: "demo"
    taxonomy: "genre"
    url: "http://localhost/type/demo/"
media_type: "Program"
download_url: "https://archive.org/download/timex-sinclair-software-archive/Color%20Show%20%28198x%29%28-%29%28TS2068%29%28US%29%28Program%29.zip"
mediadate: "198x"
media_type_tags: "Demo"
---

# Color Show

Color Show is a random color display program that plots colored spaces across the screen using a constrained random walk. The program uses RANDOMIZE to seed the random number generator, then continuously selects a random paper color (0–8) and performs up to 20 steps of a two-dimensional random walk, printing colored spaces at each position. Variables `a` and `b` track the current screen position, clamped to the ranges 1–20 (rows) and 1–30 (columns) respectively to keep output within the display area. A subroutine at line 400 draws a rectangular border using PLOT and DRAW commands before the main loop begins.

***

### Program Structure

The program is divided into two functional sections: an initialization subroutine (lines 410–460) that draws a screen border, and the main loop (lines 110–380) that performs the random color walk. Control flows as follows:

1. Line 50 calls the border-drawing subroutine at line 400 (which begins executing at line 410).
2. Line 110 seeds the random number generator with `RANDOMIZE`.
3. Lines 120 sets the initial screen coordinates: row `a=10`, column `b=20`.
4. Lines 160–380 form an infinite outer loop via `GO TO 160`, picking a new color and walk length each iteration.
5. Lines 210–370 are the inner `FOR` loop executing up to `n` steps of the random walk.

### Border Subroutine

The subroutine at lines 410–460 draws a closed rectangle using `PLOT` and four `DRAW` commands covering the full 256×176 pixel screen area. The `GO SUB 400` at line 50 targets line 400, which does not exist — execution falls through to line 410, a well-known BASIC technique to save memory by avoiding an otherwise unnecessary line.

### Random Walk Mechanics

Each outer loop iteration picks a random paper color `c` in the range 0–8 and a random step count `n` in the range 0–19. The inner loop moves the cursor by incrementing or decrementing `a` (row) or `b` (column) based on a random direction `d` (0–3):

- `d=0`: move down (`a+1`)
- `d=1`: move up (`a-1`)
- `d=2`: move right (`b+1`)
- `d=3`: move left (`b-1`)

After each move, boundary clamping is applied to keep `a` within 1–20 and `b` within 1–30, preventing `PRINT AT` from causing an out-of-range error.

### Key BASIC Idioms and Techniques

- `PAPER c` followed by `PRINT AT a,b;" "` — printing a space with a set paper color is the standard method for painting colored character cells without using `INK`.
- The boundary clamp uses four successive `IF` statements (lines 280–310) rather than structured min/max functions, which is typical for the BASIC dialect in use.
- Large line-number gaps (e.g., 50, 110, 120, 160…) leave room for future insertions without renumbering.

### Bugs and Anomalies

| Issue | Detail |
| --- | --- |
| Missing `RANDOMIZE` argument | `RANDOMIZE` at line 110 with no argument uses the system clock/frame counter, which is the intended behavior for non-deterministic seeds. |
| Color range includes 8 | `INT(RND*9)` yields 0–8; color 8 is typically “transparent” or system-dependent, which may produce unexpected results depending on the current ink/paper state. |
| Walk position not reset per color | `a` and `b` are only initialized once at line 120; the walk continues from its last position across color changes, which is likely intentional for visual continuity. |

## Source Code

```
   1 REM RANDOM COLORS
  50 GO SUB 400
 110 RANDOMIZE 
 120 LET a=10:LET b=20
 160 LET c= INT (RND*9)
 170 LET n= INT (RND*20)
 210 FOR x=0 TO n
 220 LET d= INT (RND*4)
 230 IF d=0 THEN LET a=a+1
 240 IF d=1 THEN LET a=a-1
 250 IF d=2 THEN LET b=b+1
 260 IF d=3 THEN LET b=b-1
 280 IF b >=30 THEN LET b=30
 290 IF b <=1 THEN LET b=1
 300 IF a >=20 THEN LET a=20
 310 IF a <=1 THEN LET a=1
 350 PAPER c
 360 PRINT AT a,b;" "
 370 NEXT x
 380 GO TO 160
 410 PLOT 0,0
 420 DRAW 255,0
 430 DRAW 0,175
 440 DRAW -255,0
 450 DRAW 0,-175
 460 RETURN
```