DOS Plus (also known as DOS+) is an operating system written by Digital Research, first released in 1985. It can be seen as an intermediate step between CP/M-86 and DR-DOS. Digital Research, Inc. ... CP/M-86 was a version of the CP/M operating system for the Intel 8086. ... DR-DOS is an MS-DOS-compatible operating system for IBM PC-compatible personal computers, originally developed by Gary Kildalls Digital Research and derived from CP/M-86. ...

It is able to run programs written for either CP/M-86 or MS-DOS 2.11, and can read and write the floppy formats used by both these systems. Up to four CP/M-86 programs can be multitasked, but only one DOS program can be run at a time. Microsofts disk operating system, MS-DOS, was Microsofts implementation of DOS, which was the first popular operating system for the IBM PC, and until recently, was widely used on the PC compatible platform. ... 1. ...

User interface

DOS Plus attempts to present the same command line interface as MS-DOS. Like MS-DOS, it has a command line interpreter called COMMAND.COM. There is an AUTOEXEC.BAT file, but no CONFIG.SYS. The major difference the user will notice is that the bottom line of the screen contains status information similar to: Rxvt is a VT102 terminal emulator A command line interface or CLI is a method of interacting with a computer by giving it lines of textual commands (that is, a sequence of characters) either from keyboard input or from a script. ... A command line interpreter is a computer program which reads lines of text that the user types and interprets them in the context of a given operating system or programming language. ... The title given to this article is incorrect due to technical limitations. ... AUTOEXEC.BAT is a batch file run every time the MS-DOS operating system starts, after the CONFIG.SYS file is processed. ... CONFIG.SYS is the primary configuration file of the MS-DOS and OS/2 operating systems. ...

 DDT86 ALARM UK8 PRN=LPT1 Num 10:17:30 

The left-hand side of the status bar shows running processes. The leftmost one will be visible on the screen; the others (if any) are running in the background. The right-hand side shows the keyboard layout in use (UK8 in the above example), the printer port assignment, the keyboard caps lock and num lock status, and the current time. If a DOS program is running, the status line is not shown. DOS programs cannot be run in the background. In computing, a process is, roughly speaking, a task being run by a computer, often simultaneously with many other tasks. ... The caps lock is a key on a computer keyboard. ... Num Lock is a key on the numeric keypad of most keyboards, used to switch that pad between number entry and arrow keys. ...

The keyboard layout in use can be changed by pressing Ctrl, Alt and one of the function keys F1-F5. Model showing the current redevelopment of the Kings Cross area with the Channel Tunnel Rail Link terminal behind the barrel vaulted St Pancras Station on the left. ... The Alt key on a IBM PC keyboard is either of two keys located next to the Space bar, used to change the function of a key pressed. ... A function key is a key on a computer or terminal keyboard which can be programmed so as to cause an operating system command interpreter or application program to perform certain actions. ...

Commands

DOS Plus contains a number of extra commands to support its limited multitasking features:

• ADDMEM: Sets the amount of extra memory to allocate to EXE programs.
• ALARM: A message alarm clock.
• BACKG: Allows background processes to be listed and stopped.
• COMSIZE: Sets the amount of memory to allocate to COM programs.
• PRINT: Print spooler.
• SLICE: Sets the amount of processor time to give to the foreground program.
• USER: Sets the user number to use when accessing CP/M media.

It also contains subsets of the standard DOS commands and CP/M commands - for example, it has both a built-in COPY command, and a PIP utility, both of which copy files. EXE is the common filename extension for denoting an executable file (a program) in the MS-DOS and Microsoft Windows operating systems. ... In MS-DOS and compatible DOSes, and in 8-bit CP/M, a COM file is a simple type of executable file with the file name extension (not to be confused with the . ... A list of DOS commands for Microsofts MS-DOS operating system follows. ...

The CD command can assign one of the three drives N:, O: or P: to a directory on a different drive, in a similar manner to the MS-DOS command SUBST. For example,

 CD N:=C:DATAACCOUNTS 

will cause the directory C:DATAACCOUNTS to appear as drive N:.

Internal structure

DOS Plus boots from a single file called DOSPLUS.SYS (rather than the IO.SYS / MSDOS.SYS combination of MS-DOS). This file is in the CP/M-86 CMD format, and is structured internally as a number of modules: IO.SYS is an essential part of DOS and Windows 9x. ... The MSDOS.SYS file is a hidden, system, read-only file created on the root of the boot drive. ... In CP/M-86, CMD is the filename extension used by executable programs. ...

• The BDOS kernel, which handles multitasking and implements the CP/M API.
• The XIOS, which is the machine-dependent component that performs low-level disc and character I/O.
• The DOS emulator, which converts each MS-DOS function call into one or more CP/M calls. In the case of a request to change the current directory, for example, this would translate to a series of 'open directory' calls, one for each directory in the path.
• A stub which loads COMMAND.COM when required. This stub contains the string "OS=CPCDOS", suggesting that it is based on the Concurrent DOS codebase.

The word kernel has a a variety of meanings in a several fields. ... Multiuser DOS is an operating system for IBM PC-compatible microcomputers. ...

Computers that used DOS Plus

DOS Plus was the main operating system for the non-PC compatible BBC Master 512 and the Philips Yes. PC compatible versions were supplied with the Amstrad PC-1512 and the TRAN Jasmin Turbo. Non-PC compatible X86-based computers For much of the time that Microsoft operating systems have dominated business computing, it has been a given that all computers based on Intel X86 family CPUs were IBM PC Compatibles. ... A BBC Master 128 with monitor and disk drives. ... Koninklijke Philips Electronics N.V. (Royal Dutch Philips Electronics Ltd. ... One of the first PCs from IBM - the IBM PC model 5150. ... Amstrad Consumer Electronics plc, usually known as Amstrad, is a company formed in 1968 by Sir Alan Michael Sugar in the UK, and based in Brentwood in Essex, England. ... The Amstrad PC-1512 was Amstrads mostly IBM-PC compatible home computer system. ...

References

Gilmour, Jean (1986) Amstrad Personal Computer PC1512 User Instructions