#Debug exe for dosbox how to#
#Debug exe for dosbox drivers#
#Debug exe for dosbox code#
#Debug exe for dosbox free#

One of the reasons that the link table would show asĬorrupted is that there is a back link that has a zero in Help I don't now what to do, so it hangs it self up on the If the chain is broken, MSDOS will just say to it self: This is the paragraph holding the information dos needs It keeps track of allocated memory true a chain ofĪnd now the missing one paragraph, taa taa !!! MSDOS does do some memory handling and checking, not mutch The high level languages are really good at memory management.

#Debug exe for dosbox code#

This is one of the main reasons why I prefer to use assembly from within a high-level language such as C or Pascal, to pep-up particular bits of code that need to operate with hardware or at optimal speed, rather than use it for whole programs. Whether you use a COM file or an EXE file (where the memory required is specified in the header), you are merely dumped in a vacant space and left to get on with your own memory planning. It doesn't carry out any memory management on behalf of client programs (i.e., don't use it like malloc), and any DOS program is perfectly at liberty to set any value it wants in any segment register, and write anywhere up to 64K from the place pointed to. It manages memory only to the extent of making sure it doesn't put two things in the same place. DOS is merely in the business of loading a bit of code and transfering control to that code. In 16 bit addressing there's no mechanism for remembering how big a segment ought to be, and DOS doesn't even try.

I suspect you're misunderstanding DOS memory management and 16-bit addressing. 'when i succesfully allocate LESS than 64kb, function 48h returns the segment number. COM memory usage earthandfire (Programmer) 25 Feb 06 18:14 Maximum of 639k, WHY BOTHER with functions 48h, 49h, and 4Ah in. If, like you said, DOS reserves all memory from the loading point of the program up to the When i succesfully allocate LESS than 64kb, function 48h returns the segment number.īecause a segment is 64kb in size, i can STILL write to the whole segment! after that subsequent calls to function 48h were succesful. Those few bytes (7 * 16 on win2k) are negligible anyway.Īfter your previous post i tried something else.įirst i divided my program size with 16, then i fed the result to function 4Ah Various configurations can only be explained by someone who co-wrote DOS and/or Windows. I guess the question why the available paragraphs returned are not the same on my Your description of different operation systems also makes sense. COM memory usage denc4 (Programmer)Ħ5535 * 16 = 1mb (that's the 80x86 20 line address bus).

#Debug exe for dosbox drivers#

Load its device drivers and then the DOS command shell. no, there is a interrupt table first, then the DOS andĪnd then, if no upper or high memory is used, DOS will

#Debug exe for dosbox how to#

Under un other operation system you might get the 0 para-Ĭonfusing? Yes, but I don't now how to explain it inĪbout DOS below loaded at location 00000 the answer is:

#Debug exe for dosbox free#

So under realmode DOS you will get the 0 free paragraphs, Starting at address 00000 at all but can de starting atĪnd the end of the 640k region may be it bit longer orĮven shorter, depending on what to operating system is Since the memory in use by your DOS shell is in fact not If you are running DOS under an other operating system, Program up to the maximum of 640k, minus the extended biosĭata block that is located on the adress 639k in normal Of byte beginnig at 00000 downto FFFFF I made the mistageĭOS reserves all memory from the loding point of your Since most programmers and books speak of memory as a pile I ment a paragraph is 16 bytes long not 16 kilo bytes. COM memory usage lionelhill (TechnicalUser) 22 Feb 06 13:21 Or can i just ASSUME that all memory is available to me and ignore function 48hĪnd 49h all together? (i never use any TSRs so that won't be a problem). if this is true, then why do the last three configs still return >0 I also read somewhere that DOS assigns ALL available memory to a COM file when i ran it on various systemsĪnd configurations and found the following returned: The code returns DOS error code 08h (insufficient memory) ofcourse, but in thisĬase it also returns the maximum available paragraphs. Paragraphs (paragraph=16kb?) available to my program: I used the following code in a COM file to find out the maximum number of With INT21 function 48h and 49h, memory allocation and deallocation respectively. I want more than the standard 64k in a COM file so i started experimenting How does DOS manage the memory usage of a.