Memory limits - Revision history

Asie: /* World size limit */

2026-01-04T14:31:57Z

World size limit

← Older revision		Revision as of 14:31, 4 January 2026
Line 29:		Line 29:
	\|-		\|-
	\| '''FreeDOS 1.4''' \|\| m315762 \|\| Empty CONFIG.SYS and AUTOEXEC.BAT		\| '''FreeDOS 1.4''' \|\| m315762 \|\| Empty CONFIG.SYS and AUTOEXEC.BAT
			\|-
			\| '''MS-DOS Prompt (Windows ME)''' \|\| m385826 \|\|
	\|-		\|-
	\| '''MS-DOS 6.22''' \|\| m391650 \|\| Empty CONFIG.SYS and AUTOEXEC.BAT		\| '''MS-DOS 6.22''' \|\| m391650 \|\| Empty CONFIG.SYS and AUTOEXEC.BAT

Asie: /* World size limit */

2026-01-04T14:21:54Z

World size limit

← Older revision		Revision as of 14:21, 4 January 2026
Line 30:		Line 30:
	\| '''FreeDOS 1.4''' \|\| m315762 \|\| Empty CONFIG.SYS and AUTOEXEC.BAT		\| '''FreeDOS 1.4''' \|\| m315762 \|\| Empty CONFIG.SYS and AUTOEXEC.BAT
	\|-		\|-
	\| '''MS-DOS 6.22 + HIMEM''' \|\| ~~m391650~~ \|\| DOS=HIGH~~,UMB~~, no other drivers		\| '''MS-DOS 6.22''' \|\| m391650 \|\| Empty CONFIG.SYS and AUTOEXEC.BAT
			\|-
			\| '''MS-DOS 6.22 + HIMEM + EMM386''' \|\| m432770 \|\| DOS=HIGH, no other drivers
	\|-		\|-
	\| '''FreeDOS 1.4 + HIMEMX''' \|\| m436082 \|\| DOS=HIGH,UMB + SHELLHIGH, no other drivers		\| '''FreeDOS 1.4 + HIMEMX''' \|\| m436082 \|\| DOS=HIGH,UMB + SHELLHIGH, no other drivers

Asie: /* World size limit */

2026-01-04T10:40:34Z

World size limit

← Older revision		Revision as of 10:40, 4 January 2026
Line 41:		Line 41:
	Rule of thumb advice is as follows:		Rule of thumb advice is as follows:

	* A world under '''300 kilobytes''' should run on ~~most reasonable~~ DOS ~~configurations~~.		* A world under '''300 kilobytes''' should run on almost every DOS instance including machines with only 640 KB of memory and machines with significant driver overhead.
	* A world under '''350 kilobytes''' should run on most DOS ~~configurations adjusted~~ for running games which require a lot of conventional memory.		* A world under '''350 kilobytes''' should run on most DOS instances configured for running games which require a lot of conventional memory.
	* A world under '''400 kilobytes''' should run on most ~~specialized~~ DOS ~~configurations~~ for maximizing conventional memory.		* A world under '''400 kilobytes''' should be able to run on most DOS instances specially configured for maximizing conventional memory above all else.
	* A world above around '''420 kilobytes''' will not run on most DOS configurations achievable in the real world.		* A world above around '''420 kilobytes''' will not run on most DOS configurations achievable in the real world.

Asie: /* Text window line limit */

2026-01-04T07:33:41Z

Text window line limit

← Older revision		Revision as of 07:33, 4 January 2026
Line 50:		Line 50:
	== Text window line limit ==		== Text window line limit ==

	The maximum number of lines that may be displayed in a [[text window]] is 1024. This also acts as an effective limit on the number of world files that may be present in ZZT's directory, as demonstrated [https://www.youtube.com/watch?v=yMf5e1B15zA in this video].		The maximum number of lines that may be displayed in a [[text window]] is '''1024 lines'''. This also acts as an effective limit on the number of world files that may be present in ZZT's directory, as demonstrated [https://www.youtube.com/watch?v=yMf5e1B15zA in this video].

Asie: /* World size limit */

2026-01-04T07:33:11Z

World size limit

← Older revision		Revision as of 07:33, 4 January 2026
Line 19:		Line 19:
	* dynamically allocated memory for storing the current board's state: object code and text window contents.		* dynamically allocated memory for storing the current board's state: object code and text window contents.

	As some versions of ZZT have less code and data than others, they can allow loading slightly larger worlds. In particular, SoftDisk's [[Worlds of ZZT]] is ~~comped~~ without		As some versions of ZZT have less code and data than others, they can allow loading slightly larger worlds. In particular, SoftDisk's [[Worlds of ZZT]] is compiled without the built-in editor.

	To check the amount of free memory at any time, use the <code>?+DEBUG</code> [[cheats\|cheat]]. Here are some measurements of applying this cheat on an empty world in various emulated environments:		To check the amount of free memory at any time, use the <code>?+DEBUG</code> [[cheats\|cheat]]. Here are some measurements of applying this cheat on an empty world in various emulated environments:

Asie at 07:31, 4 January 2026

2026-01-04T07:31:53Z

← Older revision		Revision as of 07:31, 4 January 2026
Line 45:		Line 45:
	* A world under '''400 kilobytes''' should run on most specialized DOS configurations for maximizing conventional memory.		* A world under '''400 kilobytes''' should run on most specialized DOS configurations for maximizing conventional memory.
	* A world above around '''420 kilobytes''' will not run on most DOS configurations achievable in the real world.		* A world above around '''420 kilobytes''' will not run on most DOS configurations achievable in the real world.

			However, these are ballparks, not exact measurements - in general, the larger a world is, the more work is required for a DOS machine to run it. Don't worry about hitting them precisely.

	== Text window line limit ==		== Text window line limit ==

	The maximum number of lines that may be displayed in a [[text window]] is 1024. This also acts as an effective limit on the number of world files that may be present in ZZT's directory, as demonstrated [https://www.youtube.com/watch?v=yMf5e1B15zA in this video].		The maximum number of lines that may be displayed in a [[text window]] is 1024. This also acts as an effective limit on the number of world files that may be present in ZZT's directory, as demonstrated [https://www.youtube.com/watch?v=yMf5e1B15zA in this video].

Asie at 07:30, 4 January 2026

2026-01-04T07:30:30Z

← Older revision		Revision as of 07:30, 4 January 2026
Line 5:		Line 5:
	== Board size limit ==		== Board size limit ==

	The maximum size of a board is '''20000 bytes''', excluding the two-byte size header at its beginning. This is caused by the memory buffer used to serialize worlds having that size - larger boards are possible, but corrupt dynamically allocated memory past the serialization buffer.		The maximum theoretical size of a board is 65535 bytes; however, the maximum size of a board in practice is '''20000 bytes''', excluding the two-byte size header at its beginning. This is caused by the memory buffer used to serialize worlds having that size - larger boards are possible, but corrupt dynamically allocated memory past the serialization buffer.

	Remember that this serialization happens every time a player tries to exit the board, using both [[board edge\|board edges]] and [[passage\|passages]], as well as whenever a player chooses to save the game. A board's size also changes dynamically as stats get created and destroyed, as well as when elements are placed and removed.		Remember that this serialization happens every time a player tries to exit the board, using both [[board edge\|board edges]] and [[passage\|passages]], as well as whenever a player chooses to save the game. A board's size also changes dynamically as stats get created and destroyed, as well as when elements are placed and removed.

Asie: /* World size limit */

2026-01-04T07:28:14Z

World size limit

← Older revision		Revision as of 07:28, 4 January 2026
Line 27:		Line 27:
	\|-		\|-
	! Environment !! ?+DEBUG !! Notes		! Environment !! ?+DEBUG !! Notes
			\|-
			\| '''FreeDOS 1.4''' \|\| m315762 \|\| Empty CONFIG.SYS and AUTOEXEC.BAT
	\|-		\|-
	\| '''MS-DOS 6.22 + HIMEM''' \|\| m391650 \|\| DOS=HIGH,UMB, no other drivers		\| '''MS-DOS 6.22 + HIMEM''' \|\| m391650 \|\| DOS=HIGH,UMB, no other drivers
	\|-
	~~\| '''FreeDOS 1.4''' \|\| m315762 \|\| Empty CONFIG.SYS and AUTOEXEC.BAT~~
	\|-		\|-
	\| '''FreeDOS 1.4 + HIMEMX''' \|\| m436082 \|\| DOS=HIGH,UMB + SHELLHIGH, no other drivers		\| '''FreeDOS 1.4 + HIMEMX''' \|\| m436082 \|\| DOS=HIGH,UMB + SHELLHIGH, no other drivers

Asie: Created page with "ZZT features a number of memory limits owing to the limitations of its 16-bit DOS platform and its programming. These limits are typically increased by patched builds, forks and source ports. The wiki discusses the limits as they apply to official ZZT builds, in particular ZZT 3.2. == Board size limit == The maximum size of a board is '''20000 bytes''', excluding the two-byte size header at its beginning. This is caused by the memory buffer used to serialize world..."

2026-01-04T07:27:43Z

Created page with "ZZT features a number of memory limits owing to the limitations of its 16-bit DOS platform and its programming. These limits are typically increased by patched builds, forks and source ports. The wiki discusses the limits as they apply to official ZZT builds, in particular ZZT 3.2. == Board size limit == The maximum size of a board is '''20000 bytes''', excluding the two-byte size header at its beginning. This is caused by the memory buffer used to serialize world..."

New page

[[ZZT]] features a number of memory limits owing to the limitations of its 16-bit DOS platform and its programming.

These limits are typically increased by patched builds, forks and source ports. The wiki discusses the limits as they apply to official ZZT builds, in particular ZZT 3.2.

== Board size limit ==

The maximum size of a board is '''20000 bytes''', excluding the two-byte size header at its beginning. This is caused by the memory buffer used to serialize worlds having that size - larger boards are possible, but corrupt dynamically allocated memory past the serialization buffer.

Remember that this serialization happens every time a player tries to exit the board, using both [[board edge|board edges]] and [[passage|passages]], as well as whenever a player chooses to save the game. A board's size also changes dynamically as stats get created and destroyed, as well as when elements are placed and removed.

== World size limit ==

The maximum size of a world is bound only by the 640 kilobytes of conventional memory present on a DOS. This memory consists of:

* memory used by DOS,
* memory used by drivers and resident programs,
* static memory used by ZZT itself,
* dynamically allocated memory for storing all boards of a loaded world,
* dynamically allocated memory for storing the current board's state: object code and text window contents.

As some versions of ZZT have less code and data than others, they can allow loading slightly larger worlds. In particular, SoftDisk's [[Worlds of ZZT]] is comped without

To check the amount of free memory at any time, use the <code>?+DEBUG</code> [[cheats|cheat]]. Here are some measurements of applying this cheat on an empty world in various emulated environments:

{| class="wikitable"
|+ ZZT 3.2 free memory on a default empty world
|-
! Environment !! ?+DEBUG !! Notes
|-
| '''MS-DOS 6.22 + HIMEM''' || m391650 || DOS=HIGH,UMB, no other drivers
|-
| '''FreeDOS 1.4''' || m315762 || Empty CONFIG.SYS and AUTOEXEC.BAT
|-
| '''FreeDOS 1.4 + HIMEMX''' || m436082 || DOS=HIGH,UMB + SHELLHIGH, no other drivers
|-
| '''DOSBox v0.74-3''' || m448931 ||
|-
| '''Zeta 1.1.2''' || m549906 || Zeta ''cheats'' by offering 736 kilobytes of conventional memory and an effective DOS memory size close to zero.
|}

Rule of thumb advice is as follows:

* A world under '''300 kilobytes''' should run on most reasonable DOS configurations.
* A world under '''350 kilobytes''' should run on most DOS configurations adjusted for running games which require a lot of conventional memory.
* A world under '''400 kilobytes''' should run on most specialized DOS configurations for maximizing conventional memory.
* A world above around '''420 kilobytes''' will not run on most DOS configurations achievable in the real world.

== Text window line limit ==

The maximum number of lines that may be displayed in a [[text window]] is 1024. This also acts as an effective limit on the number of world files that may be present in ZZT's directory, as demonstrated [https://www.youtube.com/watch?v=yMf5e1B15zA in this video].