Richard Stallman's experience with the Incompatible Timesharing System (ITS), an early operating system written in assembly language that became obsolete due to discontinuation of PDP-10, the computer architecture for which ITS was written, led to a decision that a portable system was necessary.
Pengalaman Richard Stallman dengan Incompatible Timesharing System (ITS), sistem operasi kuno yang ditulis menggunakan bahasa assembly (rakitan) yang menjadi usang karena dihentikannya PDP-10, arsitektur komputer tempat ditulisnya ITS, mengarah kepada suatu keputusan bahwa sistem portabel adalah sebuah keperluan.