mingw gcc dos compile (thanks to http://nullprogram.com/blog/2014/12/09/)

hello.c

asm (".code16gcc\n"
        "call  dosmain\n"
        "mov   $0x4C,%ah\n"
        "int   $0x21\n");

static void print(char *string)
{
    asm volatile ("mov   $0x09, %%ah\n"
            "int   $0x21\n"
    : /* no output */
    : "d"(string)
    : "ah");
}

int dosmain(void)
{
    print("Hello, World!\n$");
    return 0;
}

Makefile

CFLAGS  = -std=gnu99 -Wall -Wextra -Os -nostdlib -m32 -march=i386 \
  -Wno-unused-function \
  -ffreestanding -fomit-frame-pointer -fwrapv -fno-strict-aliasing \
  -fno-leading-underscore \
  -Wl,--nmagic,-static,-Tmingw.com.ld
all:
	gcc $(CFLAGS) -o hello.o hello.c
	objcopy -O binary hello.o hello.com

mingw.com.ld

SECTIONS
{
    . = 0x0100;
    .text :
    {
        *(.text);
    }
    .data :
    {
        *(.data);
        *(.bss);
        *(.rodata);
    }
    _heap = ALIGN(4);
}

No problem!