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 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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 * DEALINGS IN THE SOFTWARE.
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 * DEALINGS IN THE SOFTWARE.
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 */
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 */
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/*
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 * SvarCOM is a command-line interpreter.
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 *
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 * a little memory area is allocated as high as possible. it contains:
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 *  - a signature (like XMS drivers do)
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 *  - a routine for exec'ing programs
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 *  - a "last command" buffer for input history
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 *
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 * when svarcom starts, it tries locating the routine in memory.
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 *
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 * if found:
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 *   waits for user input and processes it. if execing something is required, set the "next exec" field in routine's memory and quit.
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 *
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 * if not found:
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 *   installs it by creating a new PSP, set int 22 vector to the routine, set my "parent PSP" to the routine
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 *   and quit.
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 *
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 * PSP structure
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 * http://www.piclist.com/techref/dos/psps.htm
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 *
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 *
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 *
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 * === MCB ===
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 *
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 * each time that DOS allocates memory, it prefixes the allocated memory with
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 * a 16-bytes structure called a "Memory Control Block" (MCB). This control
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 * block has the following structure:
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 *
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 * Offset  Size     Description
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 *   00h   byte     'M' =  non-last member of the MCB chain
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 *                  'Z' = indicates last entry in MCB chain
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 *                  other values cause "Memory Allocation Failure" on exit
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 *   01h   word     PSP segment address of the owner (Process Id)
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 *                  possible values:
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 *                    0 = free
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 *                    8 = Allocated by DOS before first user pgm loaded
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 *                    other = Process Id/PSP segment address of owner
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 *   03h  word      number of paragraphs related to this MCB (excluding MCB)
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 *   05h  11 bytes  reserved
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 *   10h  ...       start of actual allocated memory block
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 */
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#include <i86.h>
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#include <i86.h>
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#include <dos.h>
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#include <dos.h>
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#include <stdio.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdlib.h>
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#include <string.h>
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#include <string.h>