---
title: "Mid Range Number"
id: 57105
type: "computer_media"
slug: "mid-range-number"
url: "http://localhost/computer_media/mid-range-number/"
markdown_url: "http://localhost/computer_media/mid-range-number.md"
published_at: "2024-10-03T23:32:33+00:00"
modified_at: "2026-03-30T21:19:59+00:00"
author: "David Anderson"
featured_image:
  url: "http://localhost/wp-content/uploads/2024/10/54_MidR.png"
excerpt: "Enter a series of numbers and this program instantly finds the mid-range — the exact midpoint between the smallest and largest values you've typed in."
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: "Mathematics"
    slug: "mathematics"
    taxonomy: "genre"
    url: "http://localhost/type/mathematics/"
media_contents:
  - id: 56733
    title: "Timex Sinclair Public Domain Library Tape 1002"
    type: "computer_media"
    url: "http://localhost/computer_media/timex-sinclair-public-domain-library-tape-1002/"
media_type: "Program"
mediadate: "198x"
images:
  - url: "http://localhost/wp-content/uploads/2024/10/54_MidR.png"
media_type_tags: "Mathematics"
---

# Mid Range Number

This program calculates the mid-range of a set of numbers entered by the user. It collects values one at a time, tracking the highest and lowest seen so far, and stops when 0 is entered. The mid-range is computed at line 90 as L + ((H−L)/2), which is equivalent to the arithmetic mean of the minimum and maximum values. After displaying the result, the program loops back to line 10 to reset all variables and accept a new dataset. The REM statement at line 5 stores the program title in inverse video characters.

***

## Program Analysis

### Program Structure

The program is organized into three logical phases:

1. **Initialization (lines 10–25):** Resets all working variables — `N` (count), `M` (mid-range result), `H` (highest value), and `L` (lowest value) — to zero.
2. **Data entry loop (lines 27–80):** Prompts the user repeatedly for numbers, updates the running high/low, and exits when 0 is entered.
3. **Result and restart (lines 90–130):** Computes and displays the mid-range, then jumps back to line 10 to start a fresh session.

### Variable Usage

| Variable | Purpose |
| --- | --- |
| `N` | Count of numbers entered so far |
| `Z` | Most recently entered value |
| `H` | Running maximum value |
| `L` | Running minimum value |
| `M` | Computed mid-range result |

### Key BASIC Idioms

Lines 55 and 60 use the common idiom of checking `IF N=1` to seed both `H` and `L` with the first entered value, avoiding a false comparison against the initial zero. This is necessary because valid input could include values less than or equal to zero (though the termination sentinel of 0 complicates such cases — see Bugs section).

The mid-range formula at line 90 uses `L+((H-L)/2)` rather than the simpler `(H+L)/2`. Both are mathematically equivalent for real numbers, but the chosen form avoids potential overflow on platforms with limited numeric range — a prudent choice.

### Program Flow

The main input loop runs from line 30 back to line 30 via `GOTO 30` at line 80. The loop exits at line 40 when `Z=0`, jumping to the calculation block at line 90. After displaying the result, `GOTO 10` at line 130 resets all variables and restarts the program for a new dataset without requiring a manual `RUN`.

Note that line 45 prints each entered number back to the screen as confirmation, providing a simple running list of inputs.

### Notable Techniques

- The title at line 27 is rendered in inverse video using `%`-escaped characters, making it visually distinct as a heading.
- The `REM` at line 5 mirrors the title text also in inverse video, serving as an in-listing label.
- A `CLS` at line 100 clears the screen before the result is shown, giving a clean presentation after potentially many lines of echoed input.

### Bugs and Anomalies

- **Zero as input:** The program uses `0` as a sentinel to terminate input. This means it is impossible to include 0 as a data value in the set being analyzed, which is an undocumented limitation.
- **Negative numbers:** If the first entered number is negative, `H` and `L` are both correctly set to it via the `N=1` guards. However, subsequent negative entries will be caught by the `Z<L` and `Z>H` checks correctly, so negative data generally works as expected.
- **Single value entered:** If exactly one number is entered before 0, `H` and `L` are both set to that value, so the mid-range correctly returns that value itself.
- **No entries before 0:** If the user immediately enters 0, `H` and `L` remain 0, and the reported mid-range is 0 — a silent edge case with no error or warning message.
- **Unreferenced lines:** Lines 150 and 160 (`SAVE` and `RUN`) are never reached during normal execution; they are utility lines intended to be run manually or as part of a save/autostart workflow.

## Source Code

```
   5 REM %M%I%D% %R%A%N%G%E% %C%A%L%C%U%L%A%T%I%O%N
  10 LET N=0
  15 LET M=0
  20 LET H=0
  25 LET L=0
  27 PRINT "%M%I%D% %R%A%N%G%E% %N%U%M%B%E%R"
  28 PRINT 
  30 PRINT "ENTER A NUMBER (0 TO STOP) ";
  35 INPUT Z
  40 IF Z=0 THEN GOTO 90
  45 PRINT Z
  50 LET N=N+1
  55 IF N=1 THEN LET H=Z
  60 IF N=1 THEN LET L=Z
  65 IF Z<L THEN LET L=Z
  70 IF Z>H THEN LET H=Z
  80 GOTO 30
  90 LET M=L+((H-L)/2)
 100 CLS 
 110 PRINT "THE MID RANGE NUMBER IS ";M
 120 PRINT 
 130 GOTO 10
 150 SAVE "1005%4"
 160 RUN
```