Doors CS implements most of the library functions provided by MirageOS, though not all of them are documented directly here. For those that do not have a documentation page here, refer to the documentation provided with MirageOS. These functions are available to programs that use the MirageOS or Doors CS program headers.

• directin - scans one group of the keypad for pressed keys via direct input.
• sendbytetios - sends one byte via TI-OS linking routines.
• getbytetios - receives one byte via TI-OS linking routines.
• version - retrieves MirageOS library compatibility information.
• setvputs - sets (penrow) and (pencol) and displays a string in variable-width graphscreen font.
• setpixel - sets a specific pixel in the graph buffer to dark.
• fastcopys - copies the graph buffer to the LCD, preserving all registers.
• multhe - multiplies h*e.
• multhl - multiplies h*l.
• quittoshell - quits directly to Doors CS, regardless of stack level.
• fastline - draws a line to the graph buffer, fast.
• pixelonhl - similar to setpixel
• pixeloff - turns a specified pixel to white.
• pixelxor - xor’s a specified pixel.
• pixeltest - returns the state of a specified pixel.
• pixeloffhl - similar to pixeloff.
• pixelxorhl - similar to pixelxor.
• pixeltesthl - similar to pixeltest.
• fastlineb - draws a black line to the graph buffer.
• fastlinew - draws a white line to the graph buffer.
• fastlinex - XORs a line onto the graph buffer.
• pointonc - like pixelon, but with clipping.
• pointoffc - like pixeloff, but with clipping.
• pointxorc - like pixelxor, but with clipping.
• centertext - draws a centered string to the graph buffer in variable-width font.
• cphlbc - compares hl and bc.
• putsprite8 - like iPutSprite width height=8.
• fastcopyb - similar to iFastCopy, but using hl instead of gbuf as the memory location.
• vputsc - like vputs, but copying to both the LCD and the graph buffer.
• scrolld7 - scroll the graph buffer by 7 lines.
• vnewline - like CRLF, calling scrolld7 if necessary.
• rand127 - return a random number between 0 and 127, inclusive.
• disprle - decompress RLE-compressed image.
• cphlde - compare hl and de.
• multdehl - multiply hl and de.
• fastlined - draws a fast line with a dotted line style.
• disprlel - similar to disprle, but with a specified size.
• getnext - steps forward (high mem to low mem) through the VAT, one program at a time.
• getprev - steps backwards (low mem to high mem) through the VAT, one program at a time.
• compstrs - compare two zero-terminated strings.
• nextstr - increment through a zero-terminated string to the following string.
• fastrectangle - draws an unfilled rectangle to the graph buffer.
• gettext - like vputs, but gets input.
• gettextv - same as gettext with additional options.
• disp3spaces - displays three spaces in small (graphscreen) font.
• vputa - displays the value of the accumulator in base 10.
• compstrsn - compares two strings for a specified number of characters.
• largespritehl - similar to iLargeSprite
• setupint - sets up a simplified MirageOS interrupt tasker.
• getchecksum - (not included in Doors CS).
• freearc - gets amount of free archive (not included in Doors CS).
• swapram - swaps two areas of memory via the stack (not included in Doors CS).
• vatswap - swaps two VAT entries. Removed from Doors CS for space reasons.
• sendprog - attempt to transfer a program using TI-OS linking routines (not included in Doors CS).
• arcprog - archived program (not included in Doors CS).
• renameprog - rename program (not included in Doors CS).
• delprog - delete a specified program. (not included in Doors CS)
• filledrectangle - draws a filled rectangle.