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Emulate legacy software when the behaviour of a born-digital object — not just its content — is what you must preserve: interactive works, games, software art, and databases or applications whose meaning lives in running them. When you only need the information inside (text, a table, a static image), migrate to an open format instead, because emulation adds ongoing maintenance, copyright complications and security exposure that a simple migration avoids. The decision turns on significant properties and on whether you can sustain the environment.
What problem does emulation actually solve?
Emulation recreates the original hardware and software environment so an object runs as it did when created, while migration converts the object into a current format and accepts some loss of original behaviour. Emulation's strength is fidelity to experience: a 1996 multimedia CD-ROM, a HyperCard stack, or a dynamic spreadsheet with live macros behaves correctly only inside the software that made it. Its weakness is that you now have to keep that whole stack alive.
When should you emulate rather than migrate?
The deciding question is "what are the significant properties of this object?" If the answer includes interactivity, dynamic behaviour, or a look-and-feel that cannot survive flattening, lean toward emulation. If the answer is "the words" or "the picture", migrate.
| Object type | Significant property | Better approach |
|---|---|---|
| Word-processed letter | Text content | Migrate to PDF/A or TXT |
| Scanned image set | Pixels | Migrate to TIFF/JP2 |
| Interactive CD-ROM | Behaviour, UX | Emulate |
| Software art / game | Runtime experience | Emulate |
| Legacy database app | Query behaviour, relations | Emulate, or migrate data + document |
| Spreadsheet with macros | Computation | Emulate if logic matters; else migrate values |
What does it cost over time?
Migration is front-loaded: expensive to design per format, cheap to keep. Emulation is the opposite — quick to stand up per object, but every emulator, dependency and disk image needs sustaining as host platforms move on. Over a few decades the lifetime costs converge, so do not pick emulation expecting it to be "free" after setup.
Is it legal to emulate copyrighted software?
The emulator (QEMU, DOSBox) is generally fine to run, but the operating system and applications inside it remain under copyright. You usually need a licence or a copyright exception, and many institutions limit emulated access to on-site, screen-only sessions where the reader interacts with a running program but cannot extract the copyrighted binaries. Clear this before you build, not after.
How do you stand up an emulated environment?
For a single DOS program, DOSBox is the fastest path. For a whole machine, attach a captured disk image to QEMU. For reader delivery without local installs, use the EaaSI / Emulation-as-a-Service framework, which serves the environment to a browser.
bash
# Run a DOS application captured from a 1994 floppy
dosbox -c "mount c /work/access/budgetpro" -c "c:" -c "BUDGET.EXE"
# Boot a forensically captured disk image in QEMU (read-only, snapshot mode)
qemu-system-i386 -drive file=/work/sip-052/disk.img,format=raw,snapshot=on \
-m 64 -display gtkThe snapshot=on flag means the reader's session never writes back to your master image.
What are the risks you must contain?
Three. Accuracy drift: emulators approximate hardware and can diverge from true behaviour, so document and test against known-good output. Copyright: the system software inside is rarely yours to redistribute. Security and sensitivity: an emulated environment exposes the entire original disk, so scan for personal data first and run reader sessions in an isolated, screen-only, snapshot mode. If you cannot contain these, migration is the safer default.
Key Takeaways
- Emulate when behaviour and experience are significant properties; migrate when you only need the content.
- Decide per object by naming its significant properties before choosing an approach.
- Emulation trades low setup cost for ongoing maintenance — it is not free after the first build.
- The emulator is usually legal to run, but the OS and apps inside are copyrighted; restrict to screen-only sessions.
- Capture full disk images at transfer so you can attach them to QEMU later.
- Contain the risks: test for accuracy drift, clear copyright, and scan for sensitive data before opening any session.
Frequently Asked Questions
When is emulation the right choice over migration?
Choose emulation when behaviour and look-and-feel are significant properties — interactive works, games, software art, complex databases, or any object whose meaning depends on running in its original environment. Migration is better when you only need the content, like text or a static image.
Is emulation legal for archival access?
The emulator itself is usually fine, but the operating system and applications inside it are copyrighted. You typically need a licence or a copyright exception, and access is often restricted to on-site, screen-only sessions to stay within those limits.
What does emulation cost compared to migration?
Migration has a high one-off cost per format and low ongoing cost; emulation has a lower setup cost per object but ongoing maintenance — emulators, dependencies and disk images all need sustaining. Over decades the costs can converge.
What tools do archives use to emulate legacy software?
QEMU and VirtualBox for whole machines, DOSBox for DOS programs, and the EaaSI / Emulation-as-a-Service framework for delivering emulated environments to readers through a browser without local installs.
Can I emulate from a disk image directly?
Often yes — a raw or forensically captured disk image can be attached to QEMU or converted to a bootable virtual disk, which is why capturing full disk images during transfer pays off later.
What are the main risks of relying on emulation?
Emulators can drift from accurate behaviour, depend on copyrighted system software, and add a maintenance burden. They also expose readers to the full original environment, which raises security and sensitivity concerns you must contain.