HVI - VI Clone for CP/M

Version 1.4

A lightweight VI-compatible editor for CP/M 2.2 and CP/M 3.0, written in HI-TECH C. Uses a gap buffer for efficient editing and ANSI escape sequences for terminal control. Implements most of the basic movement and editing commands including the . operator for repeat. Also has a single level undo.

Author: Juan Orlandini
License: MIT

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Building

Requirements

• HI-TECH C Compiler for Z80/CP/M (V3.09 or later)
• CP/M 2.2 or CP/M 3.0 system with at least 48K TPA

Build Steps (on CP/M)

1. Copy all source files to a CP/M disk/drive:

HVI.C  GAP.C  TERM.C  SCREEN.C  EMOVE.C  EDIT.C  EREPEAT.C  EX.C  HVI.H

2. Compile each file individually:

C -C HVI.C
C -C GAP.C
C -C TERM.C
C -C SCREEN.C
C -C EMOVE.C
C -C EDIT.C
C -C EREPEAT.C
C -C EX.C

3. Link the object files with LINQ to produce HVI.COM:

LINQ -Z -N -C100H -OHVI.COM CRTCPM.OBJ HVI.OBJ GAP.OBJ TERM.OBJ SCREEN.OBJ EMOVE.OBJ EDIT.OBJ EREPEAT.OBJ EX.OBJ LIBC.LIB

Note: The HI-TECH C linker is named LINQ, not LINK. Adjust the -C100H load address if your TPA starts elsewhere.

Cross-Compilation (Linux/macOS host)

If using the HI-TECH Z80 cross-compiler on a Unix host:

c -c hvi.c gap.c term.c screen.c emove.c edit.c erepeat.c ex.c
linq -Z -N -C100H -ohvi.com crtcpm.obj hvi.obj gap.obj term.obj screen.obj emove.obj edit.obj erepeat.obj ex.obj libc.lib

Transfer hvi.com to your CP/M system via XMODEM, Z-Modem, or disk image.

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Usage

HVI [filename]

• filename — file to open (created if it does not exist)

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Supported Commands

Normal Mode — Movement

Key	Action
h / ←	Move left one character
l / →	Move right one character
j / ↓	Move down one line
k / ↑	Move up one line
Enter	Move to first non-blank of next line
w	Forward to start of next word
b	Backward to start of previous word
e	Forward to end of word
0	Move to beginning of line
^	Move to first non-blank of line
$	Move to end of line
G	Go to last line (or line N with count)
gg	Go to first line (or line N: 5gg)
Ctrl-F	Scroll forward one page; cursor lands in the middle of the new page. No-op if already at the end of the file.
Ctrl-B	Scroll backward one page; cursor lands in the middle of the new page. No-op if already at the beginning of the file.
Ctrl-D	Scroll forward half page
Ctrl-U	Scroll backward half page

Normal Mode — Insert / Append

Key	Action
i	Insert before cursor
a	Append after cursor
I	Insert at beginning of line
A	Append at end of line
o	Open new line below, enter insert mode
O	Open new line above, enter insert mode
s	Substitute character(s) (delete + insert)
S	Substitute entire line

Normal Mode — Delete / Change

Key	Action
x	Delete character under cursor
X	Delete character before cursor
dd	Delete current line
dw	Delete word forward
db	Delete word backward
d$	Delete to end of line
d0	Delete to beginning of line
dG	Delete to end of file
D	Delete to end of line (same as d$)
cc	Change current line
cw	Change word
c$	Change to end of line
C	Change to end of line (same as c$)
r	Replace single character
J	Join line below to current line
~	Toggle case of character

Normal Mode — Yank and Put

Key	Action
yy	Yank (copy) current line
Y	Yank current line (same as yy)
yw	Yank word
y$	Yank to end of line
p	Put (paste) after cursor / below current line
P	Put before cursor / above current line

Normal Mode — Search

Key	Action
/	Search forward for pattern
?	Search backward for pattern
n	Repeat last search
N	Repeat last search in reverse

Normal Mode — Character Search (current line)

Key	Action
f{c}	Move to next occurrence of character c on line
F{c}	Move to previous occurrence of character c on line
;	Repeat last f or F in the same direction
,	Repeat last f or F in the opposite direction

Both repeat commands accept a count prefix (e.g. 3; skips to the third next match).

Normal Mode — Miscellaneous

Key	Action
.	Repeat last change
u	Undo last change
:	Enter ex command mode
Ctrl-L	Redraw screen

Insert Mode

Key	Action
(any char)	Insert character
Enter	Insert newline
Backspace	Delete previous character
Ctrl-H	Delete previous character
Ctrl-W	Delete previous word
Ctrl-U	Delete to start of line
↑↓←→	Move cursor (stay in insert mode)
ESC	Return to normal mode

Ex Commands

Command	Action
:w	Write (save) current file
:w filename	Write to named file
:q	Quit (fails if unsaved changes)
:q!	Quit without saving
:wq	Write and quit
:wq!	Write and quit (force)
:x	Write if modified, then quit
:x!	Write and quit (force)
:e filename	Abandon current buffer and edit named file
:e! filename	Abandon modified buffer and edit named file
:r filename	Read file and insert after current line
:N	Go to line number N
:$	Go to last line

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Count Prefix

Most commands accept a numeric count prefix:

• 5j — move down 5 lines
• 3w — move forward 3 words
• 2dd — delete 2 lines
• 10G — go to line 10

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Status Line

The status line shows:

"filename" [+] L<current>/<total>

• [+] appears when the buffer has unsaved changes
• <current> is the current line number (1-based)
• <total> is the total line count in the loaded buffer

When a file is too large to fit entirely in memory, a + is appended to the total to indicate that more content exists beyond the loaded window:

"filename" [+] L42/300+

Whenever HVI reads the next chunk of a large file from disk, it briefly shows [Loading...] on the status line. The indicator is replaced by the normal status display as soon as the screen is refreshed after the load completes.

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Large File Support

HVI can open and edit files larger than available RAM. At startup it allocates the largest single block available (up to ~28 KB on a typical CP/M system) and loads as much of the file as fits, recording the byte offset where loading stopped.

As you scroll forward with j, Ctrl-D, or Ctrl-F, HVI automatically loads the next chunk from the tail. When the buffer is full, an equal number of bytes are silently discarded from the beginning of the buffer to make room. The in-memory content is therefore a sliding window over the file.

On every :w save:

1. Any bytes scrolled off the front (before the current window) are copied from the original file.
2. The in-memory (edited) content is written in CR+LF format.
3. The unloaded tail (after the current window) is appended from the original file.
4. A Ctrl-Z (0x1A) terminator is written last.

When saving to the same filename that holds the tail, HVI writes to a temporary file HVITMP.TMP first, then replaces the original, so tail data is never overwritten before it is read.

Limitation: edits are restricted to the portion of the file currently in the buffer. Content that has scrolled off the front or not yet been loaded from the tail is preserved unchanged on save.

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Terminal Requirements

HVI uses ANSI/VT100 escape sequences. It defaults to 80 columns × 24 rows, which is the standard CP/M terminal size.

At startup HVI always queries the terminal for its actual dimensions by sending ESC[999;999H (cursor to extreme bottom-right) followed by ESC[6n (ANSI cursor-position report). The response is read byte-by-byte via BIOS CONIN, bypassing BDOS canonical buffering. If the terminal does not respond within the polling timeout, HVI silently falls back to the 80 × 24 defaults — it will not hang. No recompilation flag is needed.

Compatible terminals: VT100, VT220, xterm, ANSI.SYS, and most modern terminal emulators connected via a serial port.

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File Format

HVI reads files in binary mode, stripping bare CR characters on load. On save, each LF is written as CR+LF per CP/M convention, and the file is terminated with Ctrl-Z (0x1A) per CP/M file format rules.

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Performance

HVI is designed for 9600 baud serial terminals. All screen updates are sized to the minimum needed for the operation:

Operation	Output sent
h, l, 0, ^, $, f, F, ;, ,	Cursor reposition only — no text redrawn, no status bar update
j, k, Enter, w, b, e, /, ?, n, N, gg, nG	Terminal scroll + one new line (~53 bytes) when viewport shifts by one row, or cursor reposition only when no scroll needed — status bar not updated
r replace character	Single visual row redrawn
x, X, D, ~, s, S, C	Current logical line redrawn
J, o, O, p, P, u, dw, dd, cw, Enter in insert mode	Rows from cursor to bottom redrawn (rows above cursor skipped)
G, Ctrl-F, Ctrl-B, Ctrl-D, Ctrl-U, : commands	Full screen redrawn

The "cursor to bottom" tier is the key optimization for editing operations: on a 24-row terminal with the cursor near the middle, it sends roughly half the bytes of a full screen refresh (~600 bytes vs ~1200 bytes at 9600 baud ≈ 0.5 seconds saved per keystroke).

The status bar line counter is not refreshed on every j/k/Enter/nG keypress — it updates on the next edit, search, page scroll, or Ctrl-L. The total line count is cached after the first computation and invalidated only when the buffer changes, so the status bar update itself is cheap when it does occur.

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Known Limitations

• Single-level undo only (u undoes the most recent change)
• Edits to large files are limited to the in-memory window (see Large File Support above)
• No visual/block selection mode
• No macro recording/playback
• No window splitting

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License

MIT License. Copyright (c) Juan Orlandini.