| 22,48 → 22,6 |
|---|
| * DEALINGS IN THE SOFTWARE. |
| */ |
| |
| /* |
| * SvarCOM is a command-line interpreter. |
| * |
| * a little memory area is allocated as high as possible. it contains: |
| * - a signature (like XMS drivers do) |
| * - a routine for exec'ing programs |
| * - a "last command" buffer for input history |
| * |
| * when svarcom starts, it tries locating the routine in memory. |
| * |
| * if found: |
| * waits for user input and processes it. if execing something is required, set the "next exec" field in routine's memory and quit. |
| * |
| * if not found: |
| * installs it by creating a new PSP, set int 22 vector to the routine, set my "parent PSP" to the routine |
| * and quit. |
| * |
| * PSP structure |
| * http://www.piclist.com/techref/dos/psps.htm |
| * |
| * |
| * |
| * === MCB === |
| * |
| * each time that DOS allocates memory, it prefixes the allocated memory with |
| * a 16-bytes structure called a "Memory Control Block" (MCB). This control |
| * block has the following structure: |
| * |
| * Offset Size Description |
| * 00h byte 'M' = non-last member of the MCB chain |
| * 'Z' = indicates last entry in MCB chain |
| * other values cause "Memory Allocation Failure" on exit |
| * 01h word PSP segment address of the owner (Process Id) |
| * possible values: |
| * 0 = free |
| * 8 = Allocated by DOS before first user pgm loaded |
| * other = Process Id/PSP segment address of owner |
| * 03h word number of paragraphs related to this MCB (excluding MCB) |
| * 05h 11 bytes reserved |
| * 10h ... start of actual allocated memory block |
| */ |
| |
| #include <i86.h> |
| #include <dos.h> |
| #include <stdio.h> |