diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..43ae64a
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,5 @@
+unhdcpy: decompress.c
+	gcc decompress.c -o unhdcpy -O3
+
+clean:
+	rm -f unhdcpy
diff --git a/decompress.c b/decompress.c
new file mode 100644
index 0000000..f07d8ca
--- /dev/null
+++ b/decompress.c
@@ -0,0 +1,125 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+
+int main(int argc, char *argv[])
+{
+	FILE *fp;
+	uint8_t *hdcopy;
+	uint8_t *plain;
+	uint32_t length;
+
+	int i, j, k, r;
+
+	if(argc != 3)
+	{
+		fprintf(stderr, "Usage: %s <HD-COPY Image> <IMA plain floppy image>\n\n", argv[0]);
+		fprintf(stderr, "This small tool can decompress HD-COPY image to plain floppy image.\n");
+		fprintf(stderr, "It can help you to use old HD-COPY image on modern PC,\nespecially on Virtual Machine to test out old-school softwares.\n\n");
+		fprintf(stderr, "Zhiyuan Wan <h@iloli.bid> 2018, License WTFPL.\nAlgorithm analyze from <https://github.com/ciel-yu/devnotes>. Thanks him!\n");
+		exit(-1);
+	}
+	fp = fopen(argv[1], "rb");
+	if(!fp)
+	{
+		fprintf(stderr, "Can't open source HD-COPY image!\n");
+		exit(-1);
+	}
+	fseek(fp, 0, SEEK_END);
+	length = ftell(fp);
+
+	hdcopy = malloc(length);
+	plain = malloc(0x168000);
+
+	fseek(fp, 0, SEEK_SET);
+
+	fread(hdcopy, length, 1, fp);
+
+	printf("Decoding HD-COPY Image\nInput size = %d, fitting to 1.44MB\n", length);
+	fclose(fp);
+
+	uint8_t *actualimage;
+
+	if(hdcopy[0] == 0xff && hdcopy[1] == 0x18)
+	{
+		printf("That is a HD-COPY 2.0 Image\n");
+		actualimage = hdcopy + 0x0e; /* 跳过标有卷标的文件头 */
+	}
+	else
+	{
+		printf("That is a HD-COPY 1.7 Image\n");
+		actualimage = hdcopy;
+	}
+	/* 开始解码 */
+	int maxTrackCount = actualimage[0];
+	int secPerTrack = actualimage[1];
+
+	printf("maxTrackCount = %d, secPerTrack = %d\n", maxTrackCount, secPerTrack);
+	uint8_t *dataTrack = actualimage + 2; /* 有数据的磁道表 */
+
+	uint8_t *payload = dataTrack + 168; /* 载荷段 */
+
+	uint8_t *decode_p = plain;
+
+	memset(plain, 0x00, 0x168000);
+
+	for(i = 0; i < maxTrackCount; i++)
+	{
+		for(j = 0; j < 2; j++)
+		{
+			if(dataTrack[(i * 2) + j] != 0x01)
+			{
+				decode_p += 512 * secPerTrack;
+				continue;
+			}
+			int dataLen = payload[0] + (payload[1] << 8);
+			payload += 2;
+			uint8_t escByte; /* RLE 压缩 */
+			for(k = 0; k < dataLen; k++)
+			{
+				if(k == 0)
+				{
+					escByte = payload[0];
+				}
+				else
+				{
+					if(payload[k] == escByte)
+					{
+						k++;
+						uint8_t repeatByte = payload[k++];
+						int repeat = payload[k];
+
+						for(r = 0; r < repeat; r++)
+						{
+							decode_p[0] = repeatByte;
+							decode_p ++;
+						}
+					}
+					else
+					{
+						decode_p[0] = payload[k];
+						decode_p ++;
+					}
+				}
+			}
+			payload += dataLen;
+		}
+	}
+	printf("Decode successfully, write it to file\n");
+	fp = fopen(argv[2], "wb+");
+	if(!fp)
+	{
+		fprintf(stderr, "Can't save plain floppy image!\n");
+		goto deal;
+	}
+	fseek(fp, 0, SEEK_SET);
+	fwrite(plain, 0x168000, 1, fp);
+
+deal:
+	fclose(fp);
+	free(hdcopy);
+	free(plain);
+	return 0;
+}
+