diff --git a/writer.c b/writer.c
new file mode 100644
index 0000000..8a8a00f
--- /dev/null
+++ b/writer.c
@@ -0,0 +1,250 @@
+#define _CRT_SECURE_NO_WARNINGS
+#include "stdlib.h"
+#include "string.h"
+#include "stdarg.h"
+#include "writer.h"
+
+#ifdef __cplusplus 
+extern "C" {
+#endif
+
+int init_writer_object(writer_object * const wo_p, const char * const name) {
+	FILE *fp = fopen(name, "rb+");
+	if (fp == NULL) {
+		set_last_error(wo_p, OPEN_FILE_ERROR);
+		return 0;
+	}
+	wo_p->vhd_fp = fp;
+	wo_p->fixed = 0;
+	wo_p->vaild = 0;
+	wo_p->size = 0;
+	wo_p->last_error = NO_ERROR;
+	return 1;
+}
+
+void release_writer_object(writer_object * const wo_p) {
+	fclose(wo_p->vhd_fp);
+}
+
+int vaild_vhd(writer_object * const wo_p) {
+	char vhd_cookie[9] = { 0 };
+	/* the beginning of last sector means VHD cookie */
+	fseek(wo_p->vhd_fp, -512, SEEK_END);
+	fread(vhd_cookie, 1, 8, wo_p->vhd_fp);
+	return strcmp(vhd_cookie, VHD_COOKIE_STRING) == 0 && (wo_p->vaild = 1);
+}
+
+int fixed_vhd(writer_object * const wo_p) {
+	int vhd_type;
+	/* the last sector with offset 0x3C means VHD type */
+	fseek(wo_p->vhd_fp, -512 + 0x3C, SEEK_END);
+	fread(&vhd_type, sizeof(int), 1, wo_p->vhd_fp);
+	return vhd_type == 0x02000000 && (wo_p->fixed = 1);
+}
+
+int64_t size_vhd(writer_object * const wo_p) {
+	int64_t size;
+	/* the last sector with offset 0x28 means original size */
+	fseek(wo_p->vhd_fp, -512 + 0x28, SEEK_END);
+	fread(&size, sizeof(int64_t), 1, wo_p->vhd_fp);
+	/* reverse big-endian into little-endian */
+	char *p = (char *)&size, temp;
+	int i;
+	for (i = 0; i < sizeof(size) / 2; i++) {
+		temp = *p;
+		*(p + i) = *(p + 7 - i);
+		*(p + 7 - i) = temp;
+	}
+	return wo_p->size = size;
+}
+
+int write_a_vhd_sector(writer_object * const wo_p, const int64_t lba, const vhd_sector * const sector_p) {
+	fseek(wo_p->vhd_fp, lba * 512, SEEK_SET);
+	return fwrite(sector_p->raw, 1, sector_p->vaild_bytes, wo_p->vhd_fp);
+}
+
+int64_t write_hvd_sector_from_data_file(writer_object * const wo_p, const int64_t lba, const char * const name) {
+	int vaild_bytes, written_bytes;
+	int64_t total_written_bytes = 0, lba_index = lba, lba_max = wo_p->size / 512;
+	if (lba_index < 0 || lba_index >= lba_max) {
+		set_last_error(wo_p, LBA_OUT_OF_RANGE);
+		return 0;
+	}
+
+	FILE *fp = fopen(name, "rb");
+	vhd_sector sector;
+
+	if (fp == NULL) {
+		set_last_error(wo_p, OPEN_FILE_ERROR);
+		return 0;
+	}
+
+	do {
+		vaild_bytes = fread(sector.raw, 1, 512, fp);
+		sector.vaild_bytes = vaild_bytes;
+		written_bytes = write_a_vhd_sector(wo_p, lba_index++, &sector);
+		total_written_bytes += written_bytes;
+	} while (lba_index < lba_max && vaild_bytes == 512 && written_bytes);
+
+	fclose(fp);
+	return total_written_bytes;
+}
+
+writer_error get_last_error(const writer_object * const wo_p) {
+	return wo_p->last_error;
+}
+
+void set_last_error(writer_object * const wo_p, const writer_error last_error) {
+	wo_p->last_error = last_error;
+}
+
+
+void _err_msg(const char * const fmt, ...) {
+	va_list vl;
+	va_start(vl, fmt);
+	vfprintf(stderr, fmt, vl);
+	fprintf(stderr, "\n");
+	va_end(vl);
+}
+
+int64_t get_file_size_by_name(const char * const name) {
+	fpos_t fpos_begin, fpos_end;
+	int res = 0;
+	FILE *fp = fopen(name, "rb");
+	if (fp == NULL) {
+		return 0; /* error */
+	}
+	if (fgetpos(fp, &fpos_begin)) return 0; /* error */
+	fseek(fp, 0, SEEK_END);
+	if (fgetpos(fp, &fpos_end)) return 0; /* error */
+	return fpos_end - fpos_begin;
+}
+
+int main(int argc, char **argv) {
+#define __err(s, ...) _err_msg(s, ##__VA_ARGS__);
+	writer_object wo;
+	int i, j, states = 0;
+	char cc, nc;
+
+	char *vhd_file_name = NULL, *data_file_name = NULL;
+	int64_t lba;
+	option_flag last_option_flag = 0; /* 3 options must be set up */
+
+	if (argc <= 1) {
+		__err("Fixed VHD Writer\n[-h] usage help\n[-r] specify data file name (read)\n[-w] specify VHD file name (write)\n[-a] specify LBA to writing data\n");
+		return -1;
+	}
+
+	for (i = 1; i < argc; i++) {
+		for (j = 0; argv[i][j] != '\0'; j++) {
+			cc = argv[i][j];
+			nc = argv[i][j + 1];
+
+			switch (states) {
+			case 0:
+				if (cc == '-') states = 1;
+				break;
+
+			case 1: /* after accept '-' */
+				if (cc == 'w' && nc == '\0') states = 2; /* VHD file name (write) */
+				else if (cc == 'a' && nc == '\0') states = 3; /* LBA */
+				else if (cc == 'r' && nc == '\0') states = 4; /* data file name (read) */
+				else if (cc == 'h' && nc == '\0') states = 5; /* usage help */
+				else { __err("Invaild option \'%s\'", argv[i]); return -1; }
+				break;
+
+			case 2: /* after accept '-w' */
+				vhd_file_name = argv[i];
+				last_option_flag |= FLAG_SET_VHD;
+				states = 0;
+				break;
+
+			case 3: /* after accept '-a' */
+				sscanf(argv[i], "%lld", &lba);
+				last_option_flag |= FLAG_SET_LBA;
+				states = 0;
+				break;
+
+			case 4: /* after accept '-r' */
+				data_file_name = argv[i];
+				last_option_flag |= FLAG_SET_DATA_FILE;
+				states = 0;
+				break;
+
+			case 5:
+				__err("Fixed VHD Writer\n[-h] usage help\n[-r] specify data file name (read)\n[-w] specify VHD file name (write)\n[-a] specify LBA to writing data\n");
+				return -1;
+			}
+		}
+	}
+
+	if ((last_option_flag & FLAG_SET_VHD) == 0) {
+		__err("VHD image file is not specified");
+		return -1;
+	}
+	else if ((last_option_flag & FLAG_SET_LBA) == 0) {
+		__err("LBA offset is not specified");
+		return -1;
+	}
+	else if ((last_option_flag & FLAG_SET_DATA_FILE) == 0) {
+		__err("Data file is not specified");
+		return -1;
+	}
+
+	int64_t data_file_size;
+
+	init_writer_object(&wo, vhd_file_name);
+	if (get_last_error(&wo) == OPEN_FILE_ERROR) {
+		__err("Open VHD image file error");
+		return -1;
+	}
+
+	if (!vaild_vhd(&wo)) {
+		__err("Invaild or broken VHD image file");
+		release_writer_object(&wo);
+		return -1;
+	}
+
+	if (!fixed_vhd(&wo)) {
+		__err("The VHD image is not fixed which is still not support");
+		release_writer_object(&wo);
+		return -1;
+	}
+
+	size_vhd(&wo);
+
+	/* read data from the data file, then write it to VHD image file */
+	data_file_size = get_file_size_by_name(data_file_name);
+	if (data_file_size == 0) {
+		__err("Data file is invaild");
+		release_writer_object(&wo);
+		return -1;
+	}
+
+	int64_t total_written_bytes = write_hvd_sector_from_data_file(&wo, lba, data_file_name);
+	writer_error err = get_last_error(&wo);
+	if (err == LBA_OUT_OF_RANGE) {
+		__err("LBA is out of range (0 - %d)", wo.size / 512 - 1);
+		release_writer_object(&wo);
+		return -1;
+	}
+	else if (err == OPEN_FILE_ERROR) {
+		__err("Open data file error");
+		release_writer_object(&wo);
+		return -1;
+	}
+
+	fprintf(stdout, "Data: %s\nVHD: %s (offset LBA: %lld)\nTotal bytes to write: %lld\nTotal sectors to write: %lld\nTotal bytes written: %lld\nTotal sectors written: %lld\n",
+		data_file_name, vhd_file_name, lba, data_file_size, data_file_size / 512 + (data_file_size % 512 != 0), total_written_bytes, total_written_bytes / 512 + (total_written_bytes % 512 != 0));
+
+	if (total_written_bytes <= data_file_size) {
+		fprintf(stdout, "\n!!! Detected the tail of VHD image file, the writing data has been truncated!\n");
+	}
+
+	release_writer_object(&wo);
+	return 0;
+}
+
+#ifdef __cplusplus 
+}
+#endif
\ No newline at end of file
diff --git a/writer.h b/writer.h
new file mode 100644
index 0000000..4e6649b
--- /dev/null
+++ b/writer.h
@@ -0,0 +1,54 @@
+#ifndef _FIXED_VHD_WRITER_H_
+#define _FIXED_VHD_WRITER_H_
+
+#include "stdint.h"
+#include "stdio.h"
+
+#define VHD_COOKIE_STRING "conectix"
+
+
+#ifdef __cplusplus 
+extern "C" {
+#endif
+
+typedef int BOOL;
+
+typedef struct _vhd_sector {
+	int vaild_bytes; /* 0 ~ 512 */
+	uint8_t raw[512];
+}vhd_sector;
+
+typedef enum _writer_error {
+	NO_ERROR,
+	LBA_OUT_OF_RANGE,
+	OPEN_FILE_ERROR
+}writer_error;
+
+typedef struct _writer_object {
+	FILE *vhd_fp; /* file pointer */
+	BOOL vaild;
+	BOOL fixed; /* fixed VHD flag */
+	int64_t size;
+	writer_error last_error;
+}writer_object;
+
+typedef enum _option_flag {
+	FLAG_SET_VHD = 1,
+	FLAG_SET_DATA_FILE = 2,
+	FLAG_SET_LBA = 4
+}option_flag;
+
+int init_writer_object(writer_object * const wo_p, const char * const name);
+void release_writer_object(writer_object * const wo_p);
+int vaild_vhd(writer_object * const wo_p);
+int fixed_vhd(writer_object * const wo_p);
+int write_a_vhd_sector(writer_object * const wo_p, const int64_t lba, const vhd_sector * const sector_p);
+int64_t write_hvd_sector_from_data_file(writer_object * const wo_p, const int64_t lba, const char * const name);
+writer_error get_last_error(const writer_object * const wo_p);
+void set_last_error(writer_object * const wo_p, const writer_error last_error);
+
+#ifdef __cplusplus 
+}
+#endif
+
+#endif