---
title: "Perceptions: Syncsums"
type: "article"
slug: "perceptions-syncsums"
url: "http://localhost/article/perceptions-syncsums/"
markdown_url: "http://localhost/article/perceptions-syncsums.md"
published_at: "2020-10-28T13:57:19+00:00"
modified_at: "2024-06-23T01:03:55+00:00"
featured_image:
  url: "http://localhost/wp-content/uploads/2022/04/20230809-041332.jpg"
excerpt: "Short program to provide checksums to users as they type in programs, to ensure they've been entered correctly."
category:
  - name: "SYNC"
    slug: "sync"
    taxonomy: "category"
    url: "http://localhost/category/periodicals/sync/"
post_tag:
  - name: "1982"
    slug: "year-1982"
    taxonomy: "post_tag"
    url: "http://localhost/tag/year-1982/"
  - name: "Type-in program"
    slug: "type-in-program"
    taxonomy: "post_tag"
    url: "http://localhost/tag/type-in-program/"
  - 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/"
indiv:
  - name: "David Ornstein"
    slug: "david-ornstein"
    taxonomy: "indiv"
    url: "http://localhost/indiv/david-ornstein/"
publication: "Sync"
publication_r:
  id: 10243
  title: "SYNC"
  type: "periodical"
  url: "http://localhost/periodical/sync-magazine/"
authors: "David Ornstein"
issues_articles:
  - id: 26564
    title: "SYNC Special Issue 1982"
    type: "issue"
    url: "http://localhost/issue/sync-special-issue-1982/"
pages: "12-13"
pubdate: "Special Issue 1982"
archive_link: false
volumeissue: "vn"
article_media:
  - id: 51358
    title: "Syncsum"
    type: "computer_media"
    url: "http://localhost/computer_media/syncsum/"
---

# Perceptions: Syncsums

Short program to provide checksums to users as they type in programs, to ensure they’ve been entered correctly.

## Source Code: Syncsum

```
   1 REM 217D40ED5B0C4006007CBA20087DBB2004480600C978AE472318EE
   2 REM 
   3 REM   % % %S% %Y% %N% %C% %S% %U% %M% % 
   4 REM 
   5 REM TO OBTAIN SYNCSUM, LOAD         THIS PROGRAM AND RUN IT         THEN LOAD IT AGAIN AND          ENTER "GOTO 100". THEN          LOAD YOUR MAIN PROGRAM          AND IF YOU HAVE A 16K           RAM PACK, YOU CAN ENTER         THE COMMAND PRINT USR           32741 (17381 FOR 1K OR          18405 FOR 2K). SYNCSUM          SHOULD BE CONSTANT FOR          EACH PROGRAM YOU HAVE. 
   6 FAST 
   7 REM 
   8 REM ENTER R AS THE NUMBER           OF BYTES YOU WANT TO            RESERVE ABOVE RAMTOP
   9 REM 
  10 LET R=27
  20 LET RAMTOP=PEEK (16388)+PEEK (16389)*256-R
  30 POKE 16388,RAMTOP-256*INT (RAMTOP/256)
  40 POKE 16389,INT (RAMTOP/256)
  50 NEW 
  60 NEXT B
 100 LET RT=PEEK (16388)+PEEK (16389)*256
 110 FOR B=0 TO 26
 120 LET X=((PEEK (16509+5+B*2)-28)*16+(PEEK (16509+5+B*2+1)-28))
 130 POKE RT+B,X
 140 NEXT B
 150 NEW
```