initial commit

LICENSE

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+Copyright (c) 2012 James Tauber and contributors.
+
+Permission is hereby granted, free of charge, to any person
+obtaining a copy of this software and associated documentation
+files (the "Software"), to deal in the Software without
+restriction, including without limitation the rights to use,
+copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.

README.md

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+# An Operating System for the DCPU-16
+
+See https://github.com/jtauber/dcpu16py for a Python-based emulator,
+assembler, disassembler, debugger for the DCPU-16.
+
+## Features
+
+* some basic video functions for clearing the screen and printing.

dcpu16os.asm

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+; simple operating system for the DCPU-16
+
+; until we have something like EQU, we'll just document memory locations here
+
+; vidmem    = 0x8000
+; cursor    = 0x1000
+; termwidth = 0x1001
+; termheight = 0x1002
+
+SET PC, start
+
+:banner DAT "DCPU-16 Operating System", 0
+
+:clear_screen
+    SET I, 0x8000
+    SET Z, [0x1001]
+    MUL Z, [0x1002]
+    ADD Z, 0x8000                       ; z = (termwidth * termheight) + vidmem
+:clear_screen_loop                      ; loop i through video memory
+    SET [I], 0x20                       ;    clearing screen
+    ADD I, 1
+    IFE I, Z
+        SET PC, clear_screen_done
+    SET PC, clear_screen_loop
+:clear_screen_done
+    SET [0x1000], 0                ; set cursor to top left
+    SET PC, POP ; return
+
+:println
+    JSR print
+    JSR newline
+    SET PC, POP ; return
+
+:print                              ; prints string starting at X
+    SET I, X
+:print_loop                             ; loop through string at A
+    IFE [I], 0                          ; if hit NULL
+        SET PC, POP                     ;     return
+    SET A, [I]
+    JSR print_char
+    ADD I, 1
+    SET PC, print_loop
+
+; doesn't scroll when at end yet
+:print_char                         ; print character in A
+    SET Y, [0x1000]                     ; set Y to cursor
+    SET [0x8000 + Y], A
+    ADD [0x1000], 1                     ; move cursor
+    SET PC, POP                         ; return
+
+:newline                            ; clears to end of line
+    SET Y, [0x1000]
+    MOD Y, [0x1001]                     ; y = cursor 
+    IFE Y, 0
+        SET PC, POP
+    SET [0x8000 + Y], 0x20
+    ADD [0x1000], 1
+    SET PC, newline
+
+:start
+    SET [0x1001], 80                    ; terminal width
+    SET [0x1002], 24                    ; terminal height
+    JSR clear_screen
+    SET X, banner
+    JSR println
+
+:halt
+    SET PC, halt