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I know that executables contain instructions, but what exactly are these instructions? If I want to call the MessageBox API function for example, what does the instruction look like?
Thanks.
Executables are binary files that are understood by the operating system. The executable will contain sections which have data in them. Windows uses the PE format. The PE Format has a section which has machine instructions. These instructions are just numbers which are ordered in a sequence and is understood by the CPU.
A function call to MessageBox(), would be a sequence of instructions which will
1) have the address of the function which is in a DLL. This address is put in by the compiler
2) instructions to “push” the parameters onto a stack
3) The actual function call
4) some sort of cleanup (depends on the calling convention).
Its important to remember that EXE files are just specially formatted files. I dont have a disassembly for you, but you can try compiling your code, then open your EXE in visual studio to see the disassembly.