Peter MacDonald (computer programmer) the Linux Kernel into Dynamically Loadable Modules"). MacDonald co-developed early features of the Linux kernel in the early 1990s, including shared libraries, pseudo terminals, the select call and virtual consoles. He announced Softlanding Linux System (SLS), the first standalone Linux install, for testing in August 1992 (on 15 floppy disks), and for general release in October 1992 (recommending at least 10 MB of disk space). SLS became popular, but also drew criticism. MacDonald was criticized for trying to make money on free software, but defended by Linus Torvalds. Two of the early Linux distributions were made specifically in reaction to
Operating system Digital Equipment Corporation developed many operating systems for its various computer lines, including TOPS-10 and TOPS-20 time sharing systems for the 36-bit PDP-10 class systems. Before the widespread use of UNIX, TOPS-10 was a particularly popular system in universities, and in the early ARPANET community. RT-11 was a single-user real-time OS for the PDP-11 class minicomputer, and RSX-11 was the corresponding multi-user OS. From the late 1960s through the late 1970s, several hardware capabilities evolved that allowed similar or ported software to run on more than one system. Early systems had utilized microprogramming to implement features on their systems in