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Cx Compiler: Compiler for modified C language to i386 DOS executables
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Cx Compiler

Compiler for modified C language to i386 DOS executables
Brought to you by @deathkiller


Compiler that supports modified version of C language and creates original DOS executables for i386 architecture. The executables run on MS-DOS, FreeDOS, 32-bit MS Windows using NTVDM, DosBox and other similar platforms. Currently supports several types of variables, pointers, dynamic memory allocation, branching and looping, includes and much more.

Code Quality License Lines of Code

Requires Microsoft Visual Studio 2015 or newer (or equivalent C++11 compiler) to build the solution.


  • Run Compiler.exe "Path to source code" "Path to output executable" /target:dos to compile specified source code file to executable.
  • Run Compiler.exe "Path to output executable" /target:dos to use the compiler in interactive mode and write source code directly to command line/terminal.


// Pointer types are allowed everywhere
bool BinarySearch(uint32* array, uint32 size, uint32 key, uint32* index) {
    uint32 low, high, mid;
    low = 0;
    high = (size - 1);
    while (low <= high) {
        mid = (low + high) / 2;
        if (key == array[mid]) {
            index[0] = mid;
            return true;

        if (key < array[mid]) {
            high = mid - 1;
        } else {
            low = mid + 1;
    return false;

uint8 Main() {
    // Print to console
    PrintString("Example application - Binary search\r\n");
    PrintString("Enter size of array: ");
    // Read user input
    uint32 size = ReadUint32();

    // Allocate memory on heap
    uint32* array = alloc<uint32>(size);
    if (array == null) {
        PrintString("Cannot allocate required memory block!\r\n");
        return 1;

    uint32 i;
    uint32 last = 0;
    for (i = 0; i < size; ++i) {
        PrintString("Enter #");
        PrintUint32(i + 1);
        PrintString(" number: ");
        array[i] = ReadUint32();
        if (array[i] < last) {
            PrintString("The number must be bigger than the previous one. Try it again!\r\n");
        } else {
            last = array[i];

    PrintString("Enter number to find in the array: ");
    uint32 key = ReadUint32();
    uint32 index = 0;
    // Call method with one parameter passed by reference
    bool found = BinarySearch(array, size, key, &index);
    if (found == true) {
        PrintString("The number found on position: ");
        PrintUint32(index + 1);
    } else {
        PrintString("The number was not found!\r\n");

    // Release allocated memory
    return 0;


This project is licensed under the terms of the GNU General Public License v3.0.

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