programmers quotes

Article by Ryan J. Smith

Nothing can happen on a computer without an operating system. As the interface that lets the user communicate with the machine and manage all the functions and resources of the computer, nothing could be more important than the operating system.

Older mainframe computers often used operating systems that were developed from IBM’s System/360 (or OS/360). The OS/360 pioneered a number of concepts that can still be seen in modern operating systems; some applications written for OS/360 are still usable on modern machines. One concept that was unique to the system was the fact that once a program was started, the system would keep track of all resources available, including storage, locks, data files and so on. When the process was terminated, the resources would all be reclaimed by the operating system.

For batch processing, Control Data Corporation developed the SCOPE operating system (in the 1960s) and the KRONOS and NOS systems later in the 70s. They were descendants of the archaic BASIC system, which offered early advancements in timesharing and programming languages. Control Data’s next logical step was the PLATO operating system (in conjunction with University of Illinois). PLATO used plasma panel displays and long-distance networks, and had groundbreaking advances like real-time chat and multi-user games.

Another early operating system was Burroughs’ MCP system, written in a high-level language (ESPOL). MCP (dating back to 1961) offered the first workable example of virtual memory. MCP is actually still in use today on the Unisys ClearPath line of computers. The huge front-end investment for early computers made it necessary to continue developing compatible operating systems, which partly explains why some of these ancient mainframe OS’s are still in use.

An early Operating System for “microcomputers” was the disk-based CP/M, which was closely modeled for MS-DOS, the modern OS for IBM’s PC’s. IBM’s main competition that came along in the 1980s was, of course, the Apple Macintosh and MAC OS. With the advent of the Intel 386 chip, personal computers were soon able to run multitasking OS’s, something that used to be restricted to huge mainframe machines. The chip’s 32-bit architecture paved the way for Microsoft to develop the Windows NT operating system and Apple’s MAC OS X. Over time, the next OS that would emerge would be Linux, a descendant of Unix and Minix systems. Linux would open the door to an entire open-source revolution as it was freely distributed to users, as FreeBSD, NetBSD and OpenBSD. These advances would evolve into what we know and take for granted as modern PC systems.

Today, Microsoft’s Windows OS still dominates a huge portion of the market for business computers, but each of the modern systems has its strengths and weaknesses. But regardless of the operating system, they all address the same tasks:

Memory managementDual mode operation (supervisor mode and protected mode)Virtual memoryProcess managementKernel preemptionFile managementDevice driversSecurityNetworkingFile system support