---
title: "Characters"
id: 57286
type: "computer_media"
slug: "characters-2"
url: "http://localhost/computer_media/characters-2/"
markdown_url: "http://localhost/computer_media/characters-2.md"
published_at: "2024-10-04T08:07:09+00:00"
modified_at: "2026-03-30T21:18:37+00:00"
author: "David Anderson"
featured_image:
  url: "http://localhost/wp-content/uploads/2024/10/174_Char.png"
excerpt: "A compact loop walks every character code from 0 to 255, printing each glyph in sequence — a handy one-glance reference to the full built-in character set."
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 1000"
    slug: "ts1000"
    taxonomy: "post_tag"
    url: "http://localhost/tag/ts1000/"
model:
  - name: "Timex/Sinclair 1000"
    slug: "ts-1000"
    taxonomy: "model"
    url: "http://localhost/model/ts-1000/"
genre:
  - name: "Demo"
    slug: "demo"
    taxonomy: "genre"
    url: "http://localhost/type/demo/"
media_contents:
  - id: 56734
    title: "Timex Sinclair Public Domain Library Tape 1003"
    type: "computer_media"
    url: "http://localhost/computer_media/timex-sinclair-public-domain-library-tape-1003/"
media_type: "Program"
mediadate: "198x"
images:
  - url: "http://localhost/wp-content/uploads/2024/10/174_Char.png"
media_type_tags: "Demo"
---

This program prints every character in the character set by iterating through all 256 character codes (0–255) using CHR$ and displaying each one consecutively on screen. The loop is built with a simple counter variable A, a PRINT with a semicolon suppressor to keep output continuous, and an IF/GOTO construct to repeat. The STOP at line 50 halts execution after all characters have been displayed. The SAVE line includes an inverse-video digit in the filename, and a RUN statement follows to allow immediate re-execution after loading.

***

## Program Analysis

### Program Structure

The program is a minimal character set display utility. It uses a linear flow across just five active lines:

1. `10` — Initialises counter `A` to 0.
2. `20` — Prints the character corresponding to `A` with a trailing semicolon to suppress newlines and keep output continuous.
3. `30` — Increments `A` by 1.
4. `40` — Tests whether `A < 256`; if so, loops back to line `20`.
5. `50` — Halts execution with `STOP` once all 256 codes have been printed.

Lines `60` and `70` are utility lines for saving and re-running the program and are not part of the display logic.

### Loop Mechanics

The loop iterates through values 0–255 inclusive. The condition `A < 256` at line `40` means the loop body at line `20` executes for every value of `A` from 0 to 255, giving exactly 256 iterations. After `A` reaches 255, it is incremented to 256 at line `30`, the condition at line `40` fails, and execution falls through to `STOP`.

### Key BASIC Idioms

- **Semicolon in PRINT:**`PRINT CHR$ A;` suppresses the automatic newline, so all 256 characters appear as a continuous stream filling the screen row by row.
- **IF/GOTO loop:** A classic counted loop pattern using a plain variable and a conditional branch, equivalent to a `FOR…NEXT` but slightly more explicit about the termination condition.
- **CHR$:** Converts an integer code to its corresponding display character, making this an exhaustive visual index of the entire character ROM.

### Character Coverage

Codes 0–31 on Sinclair machines are control characters (space, cursor movements, etc.) and will produce non-printing or screen-effect results rather than visible glyphs. Codes 32–127 cover the standard printable ASCII-like set. Codes 128–143 are block graphics, 144–164 are UDG slots (displaying default patterns if unprogrammed), and 165 onwards includes the keyword tokens. The output therefore gives a live map of all these regions at once.

### Notable Techniques and Observations

- Using `A < 256` rather than `A <> 256` or `A <= 255` is safe here because `A` is incremented by exactly 1 each iteration and cannot skip the boundary value.
- A `FOR A=0 TO 255 : PRINT CHR$ A; : NEXT A` construct would have been functionally equivalent and slightly more idiomatic, but the IF/GOTO approach works correctly and was common in early listings.
- No `CLS` precedes the loop, so any previous screen content remains until overwritten by the printed characters.
- The `REM` at line `1` serves only as a title label (“CHARACTERS”) and has no effect on execution.

## Source Code

```
   1 REM "CHARACTERS"
  10 LET A=0
  20 PRINT CHR$ A;
  30 LET A=A+1
  40 IF A<256 THEN GOTO 20
  50 STOP 
  60 SAVE "1017%4"
  70 RUN
```