Insert a BASIC-DOS diskette in drive A: of an IBM PC and turn the machine on. If the machine has a hard disk, BASIC-DOS first displays:
BASIC-DOS 2.00
Press a key to start...
Press any key (or wait 2 seconds) to start BASIC-DOS, or press Esc to boot from the hard disk instead. Pressing - also makes - the switch character (see SWITCHAR=). The following messages should then appear on your screen:
BASIC-DOS 2.00
Copyright (c) PCJS.ORG 1981-2026
BASIC-DOS Command Shell
A:\>
Use MEM to see memory usage. If the FPU$ driver isn’t loaded, numeric variables default to integers (see SKIP=).
The A:\> is the BASIC-DOS prompt. The prompt displays the default drive and its current directory (\ is the root directory; see CD), and indicates that BASIC-DOS is ready to accept commands from the keyboard.
Unlike PC DOS, BASIC-DOS doesn’t automatically run an AUTOEXEC.BAT file. Instead, each session’s startup command (if any) is specified on a SHELL= line in CONFIG.SYS.
The BASIC-DOS prompt accepts commands up to 254 characters long. Any characters typed beyond that limit are ignored. Press the Enter key to submit all characters currently displayed as the next command.
Other special keys include:
Other special key sequences that can be typed at any time include:
You can also use the KEYS command to display a brief summary of special keys.
A command line can contain more than one command, separated by colons (eg, CLS:DIR). BASIC-DOS commands and BASIC statements can be freely mixed, so the following is a valid command line:
FOR I = 1 TO 3:PRINT I;:NEXT
A DOS command (eg, DIR, TYPE, or the name of a program) ends at any colon outside quotes (eg, DIR *.BAS:PRINT "done"), except a colon that follows a drive letter (eg, DIR A:) or a switch’s letter (eg, FORMAT A: /F:720), or separates two digits (eg, TIME 12:30).
As in IBM PC BASIC, LET is optional for assignments, even at the prompt (eg, A = 1).
A line typed at the prompt that begins with a line number (followed by a space, or nothing at all) isn’t a command; it’s a line of BASIC that’s added to the loaded program, replacing any line with the same number. Lines are kept in line number order, so they can be typed in any order:
20 PRINT "WORLD"
10 PRINT "HELLO"
LIST
10 PRINT "HELLO"
20 PRINT "WORLD"
RUN
HELLO
WORLD
Typing a line number by itself deletes that line. Line numbers range from 1 to 65529. Since a line number must be followed by a space, programs whose names begin with digits (eg, 4DOS) can still be run by name.
The AUTO, DELETE, EDIT, and LIST commands also work with program lines, NEW erases the program, and SAVE saves it to a file.
To run a program, type its name, optionally followed by any arguments the program accepts. If you don’t specify an extension, BASIC-DOS looks for a file with the extension COM, EXE, BAT, or BAS, in that order.
For example, if a disk contains both DONKEY.COM and DONKEY.BAS, typing DONKEY runs DONKEY.COM, and typing DONKEY.BAS runs DONKEY.BAS.
If the program isn’t in the current directory, and its name doesn’t include a drive or directory, BASIC-DOS searches the directories listed in PATH$, in order. Every bootable BASIC-DOS disk has the same layout:
DIR /A lists them), and COMMAND.COM is a read-only system file (see ATTRIB)and its CONFIG.SYS sets PATH$ to the root, EXT, DEMOS, and SAMPLES (eg, A:\;A:\EXT;A:\DEMOS;A:\SAMPLES), so you can type PRIMES or DIR | SORT from any directory.
Test programs are on a separate diskette, BASIC-DOS Tests: the regression tests are in its TESTS\REGRESS directory (eg, DOSTESTS.COM; REGRESS.BAT in TESTS runs them all), other test programs (eg, GFXTEST.BAS) are in TESTS\MISC, and BENCH.BAS is in TESTS, with MSBASIC.EXE and SYMDEB.EXE in its TOOLS directory; load it in drive B: and type (for example) B:\TOOLS\MSBASIC, or B:, CD \TESTS, and REGRESS. Most of the tests can run while other sessions are busy, but HARDERR skips its tests if any other session is running a program (its disk hook would affect them).
The hard disk demo adds three more directories: TESTS (the same tests as the BASIC-DOS Tests diskette), SRC (the BASIC-DOS source code), and TOOLS (MASM and the other build tools, plus MSBASIC.EXE and SYMDEB.EXE).
Use LIST VARS to inspect the current session’s variable values and array dimensions; see LIST.
When a BAS program that you ran from the prompt ends, it remains loaded, along with its variables, so you can LIST it, examine its variables (eg, PRINT A), or RUN it again. RUN reuses the program’s compiled code (if the whole program was compiled), unless the program or its variables have changed since it was compiled.
If a name matches a BASIC keyword that can’t be used by itself (eg, CIRCLE), BASIC-DOS runs the program with that name instead (eg, CIRCLE.BAS).
To stop a program, press Ctrl-C. If the program doesn’t respond (eg, it’s in a loop that doesn’t do any input or output), press Ctrl-Break or Ctrl-Alt-Del.
The output of a command can be sent to a file instead of the screen:
DIR > FILES.TXT creates (or truncates) FILES.TXT and writes the output to itDIR >> FILES.TXT appends the output to FILES.TXTAs with other file names, a redirection file name can be quoted or a string variable (eg, DIR > F$; see Command Arguments).
Since > is also BASIC’s “greater than” operator, BASIC statements use :> (or :>>) at the end of a line instead, which redirects the output of every statement on the line (eg, PRINT "hello world" :> TEST or FOR I=1 TO 3:PRINT I:NEXT :>> TEST). :> works with any command, at the prompt and in BAT and BAS files, and its file name can be a string variable (eg, PRINT X :> F$), but it must come last on the line; for DOS commands, put a space before it (eg, DIR :> FILES.TXT), since A:>FILE still means drive A:.
The output of one command can also be sent to the input of another command, using a pipe (|):
DIR | TR a-z A-Z
Each command after the first runs in its own background session, so all commands in a pipeline run at the same time. The first command can also be a BAT or BAS file (eg, LS | SORT), which, like a built-in command, runs once the other commands have started. However, a BAT or BAS file can’t come after a |, since it would have to run in the same session as the first command (eg, DIR | TEST.BAS reports Unable to open TEST.BAS, and nothing runs). The output of a pipeline can also be redirected (eg, DIR | SORT > TEST). BASIC-DOS includes several filters for use with pipes: FIND, MORE, SORT, TEE, TR, and WC (see Filters).
At the prompt, a line of BASIC statements can end with a pipe, too, which sends the output of every statement on the line to the commands after the | (eg, FOR I=1 TO 100:PRINT 3.14^I:NEXT | MORE). The pipe must come after the line’s last statement (a | inside quotes doesn’t count), and the statements run once the other commands have started. This isn’t available in BAT and BAS files, or on low memory systems.
The input of a command can also come from a file instead of the keyboard (eg, SORT < NAMES.TXT). Input redirection applies to the first command on the line, so < must come after all of that command’s arguments and before any | or > (eg, SORT /R < NAMES.TXT > SORTED.TXT or SORT < NAMES.TXT | MORE). The input filename must be followed by the end of the line, a pipe, or output redirection.
BASIC-DOS can run several programs at once, each in its own session. A session has its own console, which can occupy the entire screen or just part of it (eg, the left and right halves of the screen, as in the BASIC-DOS Demos); the console with a double-line border is the one that has focus, which means that it receives keyboard input.
Press Shift-Tab to switch the focus to the next session.
The number of sessions and the size of their consoles are defined in CONFIG.SYS (see CONSOLE= and SESSIONS=).
The HELP command lists all commands, and HELP followed by the name of a command or function (eg, HELP MID$) displays a brief description of it.
Copyright (c) 2020-2026 Jeff Parsons Released under MIT License