XXIIVV — dos

DOS is a platform-independent acronym for Disk Operating System.

Commands

BREAK	Controls the handling of program interruption with Ctrl+C or Ctrl+Break.
CHCP	Displays or changes the current system code page.
CHDIR, CD	Changes the current working directory or displays the current directory.
CLS	Clears the screen.
COPY	Copies one file to another (if the destination file already exists, MS-DOS asks whether to replace it). (See also XCOPY, an external command that could also copy directory trees).
CTTY	Defines the device to use for input and output.
DATE	Display and set the date of the system.
DEL, ERASE	Deletes a file. When used on a directory, deletes all files inside the directory only. In comparison, the external command DELTREE deletes all subdirectories and files inside a directory as well as the directory itself.
DIR	Lists the files in the specified directory.
ECHO	Toggles whether text is displayed (ECHO ON) or not (ECHO OFF). Also displays text on the screen (ECHO text).
EXIT	Exits from COMMAND.COM and returns to the program which launched it.
LFNFOR	Enables or disables the return of long filenames by the FOR command. (Windows 9x).
LOADHIGH, LH	Loads a program into upper memory (HILOAD in DR DOS).
LOCK	Enables external programs to perform low-level disk access to a volume. (MS-DOS 7.1 and Windows 9x only)
MKDIR, MD	Creates a new directory.
PATH	Displays or changes the value of the PATH environment variable which controls the places where COMMAND.COM will search for executable files.
PROMPT	Displays or change the value of the PROMPT environment variable which controls the appearance of the prompt.
RENAME, REN	Renames a file or directory.
RMDIR, RD	Removes an empty directory.
SET	Sets the value of an environment variable; without arguments, shows all defined environment variables.
TIME	Display and set the time of the system.
TRUENAME	Display the fully expanded physical name of a file, resolving ASSIGN, JOIN and SUBST logical filesystem mappings.[3]
TYPE	Display the content of a file on the console.
UNLOCK	Disables low-level disk access. (MS-DOS 7.1 and Windows 9x only)
VER	Displays the version of the operating system.
VERIFY	Enable or disable verification of writing for files.
VOL	Shows information about a volume.

Piping

Because DOS is a single-tasking operating system, piping is achieved by running commands sequentially, redirecting to and from a temporary file.

command < filename Redirect standard input from a file or device
command > filename Redirect standard output, overwriting target file if it exists.
command >> filename Redirect standard output, appending to target file if it exists.
command1 | command2 Pipe standard output from command1 to standard input of command2
command1 ¶ command2 Commands separated by ASCII-20 (¶, invoked by Ctrl+T) are executed in sequence (chaining of commands)

DosBox

To refresh the mounted folder, use rescan.To mount a folder from the host computer:

mount c ~/path/to/folder
C:

To add a new folder to your PATH:

SET PATH=%1;C:\TC

Turbo C

To work with multiple files with Turbo C, you need to create a *.PRJ file with the name of the files to be included in your project, and set this filename under the Project menu.

MAIN.C
INCLUDE.C
EXTRAS.C

Turbo C also comes with a terminal util to compile outside of the IDE:

SET PATH=%1;C:\TC
DEL UXNEMU.EXE
TCC.EXE -ml -IC:\SRC src\UXNEMU.C
UXNEMU.EXE ROMS\SCREEN.ROM

Turbo C Guide

VGA stands for Video Graphics Array, sometimes referred to as Video Graphics Adapter.

It offers many different video modes, from 2 color to 256 color, and resolutions from 320x200 to 640x480. These notesfocus on the 256-color mode, known as mode 0x13. In mode 0x13, the screen dimensions are 320 pixels in width and 200 pixels in height. Since this is a 256-color mode, each pixel represents one byte, so the memory needed is 320*200 or 64,000 bytes.

#define 256_COLOR_MODE 0x13
#define TEXT_MODE 0x03

void
set_mode(Uint8 mode)
{
	union REGS regs;
	regs.h.ah = 0x00;
	regs.h.al = mode;
	int86(VIDEO_INT, ®s, ®s);
}

Pixels

The variable offset must be an unsigned short data type (16 bits with a range from 0 to 65,535) because the size of memory needed for mode 0x13 is 64,000 bytes. Using an unsigned short data type helps insure that we won't accidently write to an area of memory that isn't part of the video memory, which might cause our program to crash.

Uint8 *VGA = (Uint8 *)0xA0000000L;

#define SCREEN_WIDTH 320  /* width in pixels of mode 0x13 */
#define SCREEN_HEIGHT 200 /* height in pixels of mode 0x13 */

void
plot_pixel(Uint16 x, Uint16 y, Uint8 color)
{
	VGA[y * SCREEN_WIDTH + x] = color;
}

Palette

To set one color in the palette, write the color index to port 0x3C8 and then write the red, green, and blue values, in order, to port 0x3C9. The VGA only gives us 6 bits per color channel.

void
set_color(Uint8 id, Uint8 r, Uint8 g, Uint8 b){
	outp(0x03c8, id);
	outp(0x03c9, r >> 2);
	outp(0x03c9, g >> 2);
	outp(0x03c9, b >> 2);
}

VGA Tutorial