Rise of CP/M : A Brief History

        In the 70's decade, there were many companies building computer kits, and all of them were providing a monitor program of their own. (There was issue about "Portability", which I'll explain later.) These monitors were small in memory, and required very few memory space varying from a few hundred to few thousand bytes. Typically a monitor provided only a few functions ranging from 10 to 15 functions. But these programs required time and expertise to develop, debug, and build. Even worse, there was no standard monitor.Each company simply added the functions they thought that users wanted. This created a problem for application programming. Because of the different monitor programs, application programs had to be especially written for each manufacturers computer. This situation led to development of CP/M [Control Program/Monitor].
        In 1973 Gary Kildall 1973 developed the first high-level programming language for microprocessors, called PL/M. While working for intel, in the same year,Gary created CP/M as the first operating system for the new microprocessor Intel 8080. He demonstrated CP/M to Intel, but Intel had little interest in CP/M and chose to market PL/M instead.
        Later, Gary and his wife Dorothy established a company, originally called "Intergalactic Digital Research" (later renamed as Digital Research, Inc), to market CP/M. Digital Research licensed CP/M for the IMSAI 8080, a popular clone of the Altair 8800. As more manufacturers licensed CP/M, it became a standard and CP/M had to support an increasing number of hardware variations. In response, Gary pioneered the concept of a BIOS, a set of simple programs stored in the computer hardware which enabled CP/M to run on different systems without modification.
        CP/M's quick success took Gary by surprise, and he was slow to update it for high density floppy disks and hard disks. After hardware manufacturers talked about creating a rival operating system, Gary started a rush project to develop CP/M 2. By 1981, at the peak of its popularity, CP/M ran on 3,000 different computer models and DRI had $5.4 million in yearly revenues.

Sources:

Study of Computers and History of Computers since last almost 12 years.

http://www.digitalresearch.biz/CPM.HTM (Official Home Page of CP/M)
http://en.wikipedia.org/wiki/CP/M
http://en.wikipedia.org/wiki/History_of_operating_systems

See Also :

http://en.wikipedia.org/wiki/Intel_8080 (The Intel 8080 Microprocessor)
http://en.wikipedia.org/wiki/Intel_4004  (World's first Microprocessor, an entire Central Processing Unit on one single chip)

Regards,
Kiran :)

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Monitors: The Ancestors of Operating Systems

Note: This article is about the system monitors for early microchip based desktop computers. This is part of series of articles about CP/M, the operating system.
       Around 1974, when personal computing was very new, single chip microprocessors made it possible to build small, comparatively inexpensive computers. This lead to birth of several small start-up companies, which sold kits for home hobbyists who wanted to build their own computer. These kits typically contained a circuit board, a  microprocessor, some memory chips,(this means, these kits "typically" did not contain video monitors), and some additional device controller chips. These additional chips were for controlling various input and output devices like paper tape, cassette tape, and floppy disk drives.
        In early days, these computer systems had one to four kilobytes of memory, or sometimes even less. Application programs were written in machine language and/or assembly language.
        Because of this lack of memory, there was typically no operating system. But, there was a small "monitor program" usually stored in a ROM (Read Only Memory), that would allow an application to do simple common tasks, such as:
- get character from keyboard device
- output character to a device such as teleprinter or printer
- save the contents to a cassette tape or a floppy disk
- restore contents from tape or floppy

The monitors did only such basic tasks, that is all about them.

Sources :

http://en.wikipedia.org/wiki/History_of_personal_computers
http://en.wikipedia.org/wiki/History_of_operating_systems
http://en.wikipedia.org/wiki/Mark-8 

Regards,
Kiran :)

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Some Basic Concepts and Terms regarding Operating System

        Here are some basic terms and concepts regarding operating systems, and computer hardware that we will need to study actual operating systems. Without knowing these concepts it will be sort of difficult to start.
First.I was thinking to explain these terms wherever occurred, but this would have made the blog posts a little lengthy and out of track.
So I decided to put them in the very beginning.
These definitions are not 100% formal, I've kept them on a very introductory level, they'll be explained wherever required.

• Resources: A resource or a computer resource is any physical or virtual component of the computer system. Every device connected externally to a computer system is a resource. Every internal system component is a resource as well. That includes the processor (CPU), RAM ("memory" in nerd -peak), I/O devices and so on.
  Virtual system resources include virtual memory, files-systems, and so on.
• Process: An informal, most basic definition is that "a program in execution is process." A computer program is just a collections of instructions for a computer. When a computer starts to obey these instructions, that is, "starts to execute" this program, it is called as process, that is it.
• Devices: A device is a piece of hardware connected internally or externally to main computer system. (I don't know what it is called when it is not connected to the computer, every man has his flaws...) Hard disks, disc drives (CD/DVD drives), key-boards, and video monitors are typical devices to be found.
• Device Controller: In simple language, device controller is part of the motherboard, it allows the motherboard to use the device. Technically, devices have a special electronic interface, called as device controller, which helps to connect a device or a group of similar devices to a computer system. Device controllers act like a glue between devices and main computer system. Just like the gluon inside a proton or neutron, who is responsible for sticking the quarks together.
• Device Driver: (Not to be confused with device controller) This is a program which helps the software to use the hardware. (Device controller helps motherboard, device driver helps the software.) Device drivers are hardware-dependent and operating-system-specific.
• BIOS: The first task of Basic Input/Output System is to identify standard system devices such as the video display card, keyboard and mouse, hard disk drive, optical disc drive and other standard hardware. After Accomplishing this task, BIOS is responsible for loading the operating system. BIOS program is stored on a non-volatile ROM chip, present on the motherboard.Usually this ROM is made of CMOS chip.
• Kernel: Kernel is a program (actually set of programs or "module" in nerd-speak.), that is always running at all time on computer (unless it is turned off obviously, as mentioned previously.) or atleast  is always present in the main memory (RAM).
      In some cases (like Linux), the entire OS is created as one monolithic entity and this entire monolithic entity is called as kernel.
• Services: One of the major tasks of operating system is to provide an environment for the execution of program(s). The OS provides some "services" to make the programming task easier. These services are provided provided not just to the user, but to the programs as well.
      The services provided may differ from OS to OS. But still, these services can be categorized according to their functionalities.
      The most familiar services to a common user are user interface and file manipulation. (yes, this might come as surprise, but user interface is a service.)
      In current days, a graphical user interface (GUI) is the most commonly used interface, other interface being command line interface also known as line based or text based interface.
      Talking about file manipulation, a user needs to read and write files, he also needs to create and delete them, programs as well, needs to perform same tasks regarding files. It is "file system"'s job to provide these services.
• Utility Programs: The most common and informal definition is, the programs which help the OS to keep on working, but however, this definition is not completely correct.
      Utility programs are not the part of the OS kernel, but work closely with the kernel to provide the ease of use or access to the system information.