add directory study

study/sabre/os/files/Executables/EXE.txt

@@ -0,0 +1,52 @@
+offset  length  description                             comments
+----------------------------------------------------------------------
+0       word    exe file signature                      usually 4d5a
+2       word    length of last used sector in file      modulo 512
+4       word    size of file, incl. header              in 512-pages
+6       word    number of relocation table items
+8       word    size of header                          in 16-byte paragraphs
+a       word    min. paragraphs needed above program    in 16-byte paragraphs
+c       word    max. paragraphs needen above program    in 16-byte paragraphs
+e       word    displacement of stack segment in module rel. to start of prog.
+10      word    contents of SP reg. at entry
+12      word    checksum                                2's complement
+14      word    contents of IP reg. at entry
+16      word    displacement of code module             rel. to start of prog.
+18      word    offset to first relocation item in file rel. to start of prog.
+1a      word    overlay number                          0 for resident prog.
+1c      varies  variable RESERVED place
+varies  varies  relocation table
+varies  varies  variable RESERVED place
+varies  varies  program and data space
+varies  varies  stack segment
+
+The relocation table is a set of far pointers (eg: 1234:5678h) and it appears
+you just add the relocation factor to the value at that address. The relocation
+factor is the start segment of where the program is loaded.
+
+Example:
+------------------------------------------------
+code segment
+start:
+        mov     ax,seg _myseg
+code ends
+
+_myseg segment
+_myseg ends
+end start
+-------------------------------------------------
+
+ Start  Stop   Length Name               Class
+
+ 00000H 00002H 00003H CODE
+ 00010H 00010H 00000H _MYSEG
+
+-------------------------------------------------
+
+Note that _MYSEG is exactly one segment above CODE.
+
+Generated output is B8 01 00; which is "mov ax,0001"
+
+The fixup table for this file has a single entry, 0000:0001. Thus if the start
+of the program begins at segment 3562 then the "mov ax,0001" gets converted to
+"mov ax,3563".