loading of an exe or com

[suhmaamiar]

how is the loading of an exe or com file is done in,
lets say, dos ?

thanks

[Mr_Spam]

DOS loads the executable file from disk into memory, then performrms the execution of the app code via a jmp instruction.

[suhmaamiar]

this is exactly what i want to know, but how ?????

[Pype.Clicker]

i would suggest you to read the "loader and linkers" online book (check the recommended reading sticky thread
But *very* basically,

Code: Select all

int (run*)(void);
void* com=alloc(file_size("program.com"));
file_map(com,"program.com");
run=com;
return run();

[Mr_Spam]

well, DOS calls the BIOS to load sectors from the disk into memory, (bios int 13). then transfering processes execution with a jmp instruction to the location in memory where DOS told the bios to put the program. it dose't get any more simple than that.

[ghostbustor]

Hi !

First u must Load the File into Memory and then Jump to its Start, the rest makes the File

[slacker]

i look at a file as a chunk of memory that isnt accessible until put into memory. it can be code or data.