Click on image to enlarge.
Sections: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | Index | Next >
Learning objective: Explain the role of MS-DOS and the CLI in Windows
Click on image to enlarge.
As you go through this unit, keep in mind that we are not learning MS-DOS but the command line interface of Windows which is *based* on MS-DOS. The commands and concepts of the command line interface (CLI) of Windows are based on the use of MS-DOS commands for backwards compatibility. The more you know about MS-DOS, the better prepared you will be to understand the CLI of Windows.
MS-DOS is many things. It is a text based command line operating system that supports a single-user doing a single task. It was Microsoft's first operating system to support IBM's first PC. It has lots of commands that have evolved over time. DOS is messy and not always consistent in how commands are executed from version to version. It is based on 16-bit architecture designed to run on the Intel 8086 processor chosen by IBM. Despite how dated MS-DOS is, DOS skills are still in use today and key components of Windows 7 and 8!
MS-DOS is an operating system for x86-based personal computers. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid 1990s, until it was gradually superseded by operating systems offering a graphical user interface (GUI), in particular by various generations of the Microsoft Windows operating system. [Wikipedia]
Based on QDOS and CP/M
MS-DOS was a renamed form of 86-DOS -- informally known as the Quick-and-Dirty Operating System or Q-DOS -- owned by Seattle Computer Products, written by Tim Paterson. Microsoft needed an operating system for the then-new Intel 8086 but it had none available, so it bought 86-DOS for $75,000 and licensed it as its own then released a version of it as MS-DOS 1.0. Development started in 1981, and MS-DOS 1.0 was released with the IBM PC in 1982. (86-DOS, in turn, was a clone of Digital Research's CP/M (for 8080/Z80 processors), ported to run on 8086 processors and with two notable differences compared to CP/M, an improved disk sector buffering logic and the introduction of FAT12 instead of the CP/M filesystem. This became possible because of the increased availability of RAM compared to what was typically available when CP/M was designed originally.) [Wikipedia]
Originally MS-DOS was designed to be an operating system that could run on any 8086-family computer. Each computer would have its own distinct hardware and its own version of MS-DOS, similar to the situation that existed for CP/M, and with MS-DOS emulating the same solution as CP/M to adapt for different hardware platforms. To this end, MS-DOS was designed with a modular structure with internal device drivers, minimally for primary disk drives and the console, integrated with the kernel and loaded by the boot loader, and installable device drivers for other devices loaded and integrated at boot time. The OEM would use a development kit provided by Microsoft to build a version of MS-DOS with their basic I/O drivers and a standard Microsoft kernel, which they would typically supply on disk to end users along with the hardware. Thus, there were many different versions of "MS-DOS" for different hardware, and there is a major distinction between an IBM-compatible (or ISA) machine and an MS-DOS [compatible] machine. Some machines, like the Tandy 2000, were MS-DOS compatible but not IBM-compatible, so they could only run software written exclusively for MS-DOS without dependence on the peripheral hardware of the IBM PC architecture. [Wikipedia]
Versions of MS-DOS
Significant releases of MS-DOS would include: Version 2X which introduced subdirectories, command input/output redirection, and pipes. Microsoft decided to use backslashes as pathname separators rather than slashes as on Unix apparently due to the latter character being used as the switch character in most DOS. Version 3X introduced support for Microsoft networking, support for 3.5 inch, and hard disk partitions of up to 32 megabytes, one primary and one "logical drive" in an "extended partition". Version 5X introduced online help, memory management, full-screen editor, and the QBasic programming language. Version 7X was embedded in Windows 95 and continues as the CLI for all subsequent versions of Windows. It supports logical block addressing and long file names.
Legal issues with system vendors
Prior to 1995, Microsoft licensed MS-DOS (and Windows) to computer manufacturers under three types of agreement: per-processor (a fee for each system the company sold), per-system (a fee for each system of a particular model), or per-copy (a fee for each copy of MS-DOS installed). The largest manufacturers used the per-processor arrangement, which had the lowest fee. This arrangement made it expensive for the large manufacturers to migrate to any other operating system, such as DR DOS. In 1991, the U.S. government Federal Trade Commission began investigating Microsoft's licensing procedures, resulting in a 1994 settlement agreement limiting Microsoft to per-copy licensing. Digital Research did not gain by this settlement, and years later its successor in interest, Caldera, sued Microsoft for damages. It was believed that the settlement ran in the order of $150m, but was revealed in November 2009 with the release of the Settlement Agreement to be $280m. [Wikipedia]
Legacy compatibility
Later versions (Windows 95, Windows 98 and Windows Me) used the DOS boot process to launch itself into protected mode. Basic features related to the file system, such as long file names, were only available to DOS when running as a subsystem of Windows. Windows NT ran independently of DOS but included a DOS subsystem so applications could run in a virtual machine under the new OS. With the latest Windows releases, even dual-booting MS-DOS is problematic as DOS may not be able to read the basic file system. [Wikipedia]
Thinking: Why does Windows 7 support MS-DOS today?
Key terms: CLI, DOS, compatibility
Resources:
To maximize your learning, please visit these Web sites and review their content
to help reinforce the concepts presented in this section.
Quick links:
MS-DOS @ Wikipedia
Notes on navigation: Click inside the frame to navigate the embedded Web page. - Click outside the frame to navigate this page to scroll up/down between the embedded Web pages. - Click on the frame title to open that page in a new tab in most browsers. - Click on the the "Reload page" link to reload the original page for that frame.
MS-DOS @ Wikipedia |
Reload page
|
If frame is empty, click on the link to view the page in a new tab or window
Sections: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | Index | Next >