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Movements, leaders, victories and the continuing fight for equality.
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Movements, leaders, victories and the continuing fight for equality.
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Meet the people whose lives, choices and achievements shaped the journey.
Black towns, communities, institutions and places where history happened.
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Katherine Johnson’s mathematical calculations helped guide some of America’s most important early space missions while she confronted the racial and gender barriers faced by Black women in twentieth-century America.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
| Command Prompt | |
|---|---|
 | |
| Other names |
|
| Developers | Microsoft, IBM, ReactOS contributors |
| Release | December 1987 |
| Operating system |
|
| Platform | IA-32, x86-64, ARM (and historically DEC Alpha, MIPS, PowerPC, and Itanium) |
| Predecessor | COMMAND.COM |
| Type | Command-line interpreter |
Command Prompt, or Windows Command Processor, is a shell program on later versions of Windows (NT and CE families), OS/2,[1] eComStation, ArcaOS, and ReactOS.[2] In some versions of Windows (CE .NET 4.2,[3] CE 5.0[4] and Embedded CE 6.0[5]) it is referred to as the Command Processor Shell. Implementation differs between operating systems, but with significant consistency of behavior and available commands.
Older, related operating systems, DOS and Windows 9x, provided COMMAND.COM as the shell. Command Prompt (cmd.exe) replaced COMMAND.COM in the Windows product line with the introduction of NT. Current versions of Windows include PowerShell as an alternative shell that runs side-by-side with Command Prompt.
The initial version of Command Prompt for Windows NT was developed by Therese Stowell.[6] Windows CE 2.11 was the first embedded Windows release to support a console and a Windows CE version of Command Prompt.[7] The ReactOS implementation of Command Prompt is derived from FreeCOM, the FreeDOS command line interpreter.[2]
In Windows, the shell is presented in the desktop via Windows Terminal or on older versions via Windows Console.
In OS/2 and Windows, the shell supports pipes to allow both sides of a pipeline to run concurrently. As a result, it is possible to redirect the standard error stream. In contrast, COMMAND.COM uses temporary files, and runs the two sides serially, one after the other.
Multiple commands can be included in a single line using the command separators &, && or ||.[8]
With the & separator, a subsequent command is executed even if the previous command indicates an error.[9] In the following example, each of the three commands is executed, one after the other, and regardless of their exit code.
>CommandA & CommandB & CommandC
With the && separator, a command must succeed, i.e. yield the exit code 0, for the subsequent command to execute. In the following example, CommandB only executes if CommandA completes successfully, and CommandC only executes if CommandB also completes successfully.
>CommandA && CommandB && CommandC
With the || separator, a command must fail, i.e. yield an exit code not equal 0, for the subsequent command to execute. In the following example, CommandB executes if CommandA fails, and CommandC executes if CommandB succeeds.
>CommandA || CommandB && CommandC
The shell limits the length of a command line which includes entered text, individual environment variables that are inherited by other processes, and all environment variable expansions[10] On Windows XP and later, the maximum length is 8191 (213-1) characters. On earlier versions, such as Windows 2000 or Windows NT 4.0, the maximum length is 2047 (211-1) characters.
The shell reserves the following characters as special:[8] &<>[]{}^=;!'+,`~ and whitespace. In some cases, an argument that contains such characters must be enclosed in double quotes to escape from the special character handling. For example:
>echo me & you
me
'you' is not recognized as an internal or external command,
operable program or batch file.
>echo "me & you"
"me & you"
The following sections list internal commands for implementations of the shell on various operating systems.
Internal commands in OS/2:[11]
Internal commands in Windows NT and later:[12]
Internal commands in Windows CE .NET 4.2,[13] Windows CE 5.0[14] and Windows Embedded CE 6.0:[15]
The net command is available as an external command.
Internal commands in ReactOS:[2]
On Windows, cmd.exe provides various user experience enhancements as compared to COMMAND.COM, including:
HELP command can then be issued with the error message number to obtain further information.SETLOCAL EnableDelayedExpansion, allowing values of variables to be calculated at runtime instead of during parsing of script before execution (Windows 2000 and later), fixing DOS idioms that made using control structures hard and complex.[16] The extensions can be disabled, providing a stricter compatibility mode.DELTREE command was merged into the rd command via the /S switch.SetLocal and EndLocal commands limit the scope of changes to the environment. Changes made to the command line environment after SetLocal are local to the batch file. EndLocal restores the previous settings.[17]call command allows subroutines within batch file. The COMMAND.COM CALL command only supports calling external batch files.set command are comparable with C shell.[further explanation needed]set command can perform expression evaluation.for command supports parsing files and arbitrary sets in addition to file names.pushd and popd commands provide access past navigated paths similar to forward and back buttons in a web browser or File Explorer.if command can perform case-insensitive comparisons and numeric equality and inequality comparisons in addition to case-sensitive string comparisons. This was available in DR-DOS, but not in PC DOS or MS-DOS.
Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
Command Prompt, or Windows Command Processor, is a shell program on later versions of Windows (NT and CE families), OS/2, eComStation, ArcaOS, and ReactOS. In some versions of Windows (CE .NET 4.2, CE 5.0 and Embedded CE 6.0) it is referred to as the Command Processor Shell. Implementation differs between operating systems, but with significant consistency of behavior and available commands. Older, related operating systems, DOS and Windows 9x, provided COMMAND.COM as the shell. Command Prompt (cmd.exe) replaced COMMAND.COM in the Windows product line with the introduction of NT. Current versions of Windows include PowerShell as an alternative shell that runs side-by-side with Command Prompt. The initial version of Command Prompt for Windows NT was developed by Therese Stowell. Windows CE 2.11 was the first embedded Windows release to support a console and a Windows CE version of Command Prompt. The ReactOS implementation of Command Prompt is derived from FreeCOM, the FreeDOS command line interpreter.
CP/M, originally standing for Control Program/Monitor and later Control Program for Microcomputers, is a mass-market operating system created in 1974 for Intel 8080-based microcomputers by Gary Kildall of Digital Research, Inc. CP/M is a disk operating system and its purpose is to organize files on a magnetic storage medium, and to load and run programs stored on a disk. Initially confined to single-tasking on 8-bit processors and no more than 64 kilobytes of memory, later versions of CP/M added multi-user variations and were migrated to 16-bit processors. CP/M's core components are the Basic Input/Output System (BIOS), the Basic Disk Operating System (BDOS), and the Console Command Processor (CCP). The BIOS consists of drivers that deal with devices and system hardware. The BDOS implements the file system and provides system services to applications. The CCP is the command-line interpreter and provides some built-in commands. CP/M eventually became the de facto standard and the dominant operating system for microcomputers, in combination with the S-100 bus computers. This computer platform was widely used in business through the late 1970s and into the mid-1980s. CP/M increased the market size for both hardware and software by greatly reducing the amount of programming required to port an application to a new manufacturer's computer. An important driver of software innovation was the advent of (comparatively) low-cost microcomputers running CP/M, as independent programmers and hackers bought them and shared their creations in user groups. CP/M was eventually displaced in popularity by DOS following the 1981 introduction of the IBM PC.
MS-DOS ( em-ess-DOSS; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its alternate branding as IBM PC DOS, and a few operating systems attempting to be compatible with MS-DOS, are sometimes referred to as "DOS" (which is also the generic acronym for disk operating system). MS-DOS was the main operating system for IBM PC compatibles during the 1980s, from which point it was gradually superseded by operating systems offering a graphical user interface (GUI), in various generations of the graphical Microsoft Windows operating system. IBM licensed and released it in 1981 as PC DOS 1.0 for use in its IBM Personal Computer. Although MS-DOS and PC DOS were initially developed in parallel by Microsoft and IBM, the two products diverged after twelve years, in 1993, with recognizable differences in compatibility, syntax and capabilities. Beginning in 1988 with DR-DOS, several competing products were released for the x86 platform. Initially, MS-DOS was targeted at Intel 8086 processors running on computer hardware using floppy disks to store and access not only the operating system, but application software and user data as well. Progressive version releases delivered support for other mass storage media in ever greater sizes and formats, along with added feature support for newer processors and rapidly evolving computer architectures. Ultimately, it was the key product in Microsoft's development from a programming language company to a diverse software development firm, providing the company with essential revenue and marketing resources. It was also the underlying basic operating system on which early versions of Windows ran as a GUI. MS-DOS went through eight versions, until development ceased in 2000; version 6.22 from 1994 was the final standalone version, with versions 7 and 8 serving mostly in the background for loading Windows 9x. The command interpreter, COMMAND.COM, runs when no application program is running. When an application exits, the interpreter resumes – loaded back into memory by the DOS if it was purged by the application. A command is processed by matching input text with either a built-in command or an executable file located on the current drive and along the command path. A command with significant program size or used infrequently tended to be a separate file in order to limit the size of the command processor program.
COMSPEC or ComSpec is one of the environment variables used in DOS, OS/2 and Windows, which normally points to the command-line interpreter, which is by default COMMAND.COM in DOS, Windows 95, 98, and ME or CMD.EXE in OS/2 and Windows NT. The variable name is written in all-uppercase under DOS and OS/2. Under Windows, which also supports lowercase environment variable names, the variable name is defined as ComSpec in the environment block, but as COMSPEC inside the DOS emulator NTVDM. When not present in the environment block, the command processor CMD.EXE of Windows NT sets COMSPEC to its own full path; it evaluates COMSPEC, for example, to execute builtin commands in pipelines and to execute command lines with its builtin FOR command. The variable's contents can be displayed by typing SET COMSPEC or ECHO %COMSPEC% at the command prompt. The environment variable by default points to the full path of the command-line interpreter. It can also be made by a different company or be a different version. Another use of this environment variable is on a computer with no hard disk, which needs to boot from a floppy disk, is to configure a RAM disk. The COMMAND.COM file is copied to the RAM disk during boot, and the COMSPEC environment variable is set to the new location on the RAM disk. This way the boot disk can be removed without the need to reinsert it after a big application has been stopped. The command-line interpreter will be reloaded from the RAM disk instead of the boot disk.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Mae Jemison, aboard Space Shuttle Endeavour in 1992.
