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


BREAKControls the handling of program interruption with Ctrl+C or Ctrl+Break.
CHCPDisplays or changes the current system code page.
CHDIR, CDChanges the current working directory or displays the current directory.
CLSClears the screen.
COPYCopies 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).
CTTYDefines the device to use for input and output.
DATEDisplay and set the date of the system.
DEL, ERASEDeletes 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.
DIRLists the files in the specified directory.
ECHOToggles whether text is displayed (ECHO ON) or not (ECHO OFF). Also displays text on the screen (ECHO text).
EXITExits from COMMAND.COM and returns to the program which launched it.
LFNFOREnables or disables the return of long filenames by the FOR command. (Windows 9x).
LOADHIGH, LHLoads a program into upper memory (HILOAD in DR DOS).
LOCKEnables external programs to perform low-level disk access to a volume. (MS-DOS 7.1 and Windows 9x only)
MKDIR, MDCreates a new directory.
PATHDisplays or changes the value of the PATH environment variable which controls the places where COMMAND.COM will search for executable files.
PROMPTDisplays or change the value of the PROMPT environment variable which controls the appearance of the prompt.
RENAME, RENRenames a file or directory.
RMDIR, RDRemoves an empty directory.
SETSets the value of an environment variable; without arguments, shows all defined environment variables.
TIMEDisplay and set the time of the system.
TRUENAMEDisplay the fully expanded physical name of a file, resolving ASSIGN, JOIN and SUBST logical filesystem mappings.[3]
TYPEDisplay the content of a file on the console.
UNLOCKDisables low-level disk access. (MS-DOS 7.1 and Windows 9x only)
VERDisplays the version of the operating system.
VERIFYEnable or disable verification of writing for files.
VOLShows information about a volume.


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


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

mount c ~/path/to/folder

To add a new folder to your PATH:


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.


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


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

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


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 */

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


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.

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);