Editing IBM 5100 (section)

==Emulator in microcode==
{{main|IBM PALM processor}}
The 5100 was based on IBM's innovative concept that, using an [[emulator]] written in [[microcode]], a small and relatively cheap computer could run programs already written for much larger, and much more expensive, existing computers, without the time and expense of writing and debugging new programs.<ref name=PALM.APL1130Board>salvaging a huge IBM 1130 APL program {{cite magazine
   |magazine=[[PC Magazine]]
   |url=https://books.google.com/books?id=q8fwTt09_MEC&pg=RA5-PA9-IA1
   |title=What is a Personal Computer? |date=November 1983}}</ref>

Two such programs were included:  a slightly modified version of APLSV, IBM's APL interpreter for its [[System/370]] mainframes, and the BASIC interpreter used on IBM's [[System/3]] minicomputer.  Consequently, the 5100's microcode was written to emulate most of the functionality of both a System/370 and a System/3.

IBM later used the same approach for its 1983 introduction of the [[XT/370]] model of the [[IBM PC]], which was a standard [[IBM Personal Computer XT|IBM PC XT]] with the addition of a System/370 emulator card.