Updating the Z-Machine Standard Documents

§6.2

Global variables (variable numbers $10 to $ff) are stored in a table in the Z-machine’s dynamic memory, at a byte address given in word 6 of the header. The table consists of 240 2-byte words and the initial values of the global variables are the values initially contained in the table. (It is legal for a program to alter the table’s contents directly in play, though not for it to change the table’s address.)

In short, there isn’t always 240 globals. See discussion here.

Zilf make the globals table as big as the actual used globals. Infocom did the same from 1987-.

List of Infocom games (from The Obsessively Complete Infocom Catalog with an array less than 240 globals.

abyss-r1-s890320.z6
arthur-r40-s890502.z6
arthur-r41-s890504.z6
arthur-r54-s890606.z6
arthur-r63-s890622.z6
arthur-r74-s890714.z6
beyondzork-beta-r1-s870715.z5
beyondzork-r47-s870915.z5
beyondzork-r49-s870917.z5
beyondzork-r51-s870923.z5
beyondzork-r57-s871221.z5
beyondzork-r60-s880610.z5
borderzone-r9-s871008.z5
hitchhiker-invclues-r31-s871119.z5
journey-dev-r142-s890205.z6
journey-dev-r46-s880603.z5
journey-r10-s890313.z6
journey-r11-s890304.z6
journey-r2-s890303.z6
journey-r26-s890316.z6
journey-r3-s890310.z6
journey-r30-s890322.z6
journey-r5-s890310.z6
journey-r51-s890522.z6
journey-r54-s890526.z6
journey-r76-s890615.z6
journey-r77-s890616.z6
journey-r79-s890627.z6
journey-r83-s890706.z6
leathergoddesses-invclues-r4-s880405.z5
minizork-r34-s871124.z3
minizork2-r2-s871123.z3
planetfall-r39-s880501.z3
plunderedhearts-r26-s870730.z3
restaurant-r15-s880512.z5
restaurant-r184-s890412.z6
sherlock-dev-r97-s871026.z5
shogun-r278-s890209.z6
shogun-r278-s890211.z6
shogun-r279-s890217.z6
shogun-r280-s890217.z6
shogun-r281-s890222.z6
shogun-r282-s890224.z6
shogun-r283-s890228.z6
shogun-r284-s890302.z6
shogun-r286-s890306.z6
shogun-r288-s890308.z6
shogun-r289-s890309.z6
shogun-r290-s890311.z6
shogun-r291-s890313.z6
shogun-r292-s890314.z6
shogun-r295-s890321.z6
shogun-r311-s890510.z6
shogun-r320-s890627.z6
shogun-r321-s890629.z6
shogun-r322-s890706.z6
wishbringer-invclues-r23-s880706.z5
zork0-alpha-r96-s880224.z5
zork0-beta-r242-s880830.z6
zork0-demo-r366-s890323.z6
zork0-demo-r393-s890714.z6
zork0-ibm-r392-s890714.z6
zork0-oldparser-r1-s871030.z5
zork0-prealpha-r74-s880114.z5
zork0-r153-s880510.z5
zork0-r242-s880901.z6
zork0-r296-s881019.z6
zork0-r343-s890217.z6
zork0-r366-s890323.z6
zork0-r383-s890602.z6
zork0-r387-s890612.z6
zork0-r393-s890714.z6
zork0-r66-s890111.z6
zork1-german-beta-r3-s880113.z5
zork1-german-r15-s890613.z6
zork1-invclues-r52-s871125.z5
zork1-r119-s880429.z3
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