CP/M Editors

Creating text files, e.g. program sources, requires a utilty to write edited data from keyboard into a file. Such a program is called an editor. If the text has to be changed, the editor reads the file and starts working on.

In the beginning, editors were working line oriented, such as ED.COM. The editor commans were difficult to understand. For example, to delete the fourth line in a file, the following commands must be typed:

Editing became easier establishing screen oriented terminals (in those days called CRTs, Cathode Ray Tubes). Now the cursor could be placed anywhere on the screen.

The base for the text characters is the seven bit ASCII code. This code involves 128 chracters, whereof 33 are non-printing control characters.

Control characters are used for the movement of the cursor accordingly. But the 33 available characters were not enough to represent all existing commands. Therefore subcommands were implemented, called by main control characters (e.g. ^K or ^Q are such controls). Introduction of WordStar, a word processor application, resulted in a quasi standard of control characters as used by this program.

Other control sequences are used to position the cursor on the screen. Many of these sequences started with the ESC character (0x1B), followed by a printable ASCII character. The sequences were inconsistent; some used column followed by row, other used row followed by column. This applies also to the cursor position. (This could be ASCII numbers or binary values. Some binaries must add an offset to represent a printable character. Find an overview for some control sequences here). A standardisation took place by introducing ANSI ESCape sequences).

Clarity is the benefit of displaying an entire file on screen. However, there are only CP/M full screen editors known to me which are loading the entire file into memory. Therefore the size of a file to be taken will be limited by the available memory. Line oriented editors, such as ED.COM, allow loading a file in parts. Therefore the size of a file is limited by disk space only. A compromise selecting a full screen editor must be found: the editor should be as small as possible, but with a large range of functionality.

Some comfortable full screen editors were availbale on SIG/M1:

1. VDO (6,75k - 54 records)
2. VDE (12k - 96 records)

The German company ACW-Soft modified the editor VDO for the JOYCE, and offered it, called EDY.COM (6,75k - 54 records). Also the company HiSoft was selling an editor in many of their software bundles, called ED80.COM (8,6k - 69 records) — my favourite one in those days.
The smallest editor known to me was TINYED.COM (5k - 40 records).