diff --git a/include/stdio.h b/include/stdio.h
index 89deb0f..00621ea 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -2,5 +2,37 @@
 #ifndef __STDIO_H__
 #define __STDIO_H__
 
+#include <sys/types.h>
+
+typedef struct FILE {
+    int			in_use;
+    uint64_t		fd;		/* Kernel File Descriptor */
+    fpos_t		offset;
+} FILE;
+
+#define SEEK_SET	0
+#define SEEK_CUR	1
+#define SEEK_END	2
+
+#define EOF		(-1)
+
+extern FILE *stdin;
+extern FILE *stdout;
+extern FILE *stderr;
+
+#define FOPEN_MAX	16
+
+FILE *fopen(const char *path, const char *mode);
+int fclose(FILE *fh);
+int feof(FILE *fh);
+int fflush(FILE *fh);
+size_t fread(void *buf, size_t size, size_t nmemb, FILE *fh);
+size_t fwrite(const void *buf, size_t size, size_t nmemb, FILE *fh);
+
+int fputc(int ch, FILE *fh);
+int fputs(const char *str, FILE *fh);
+int fgetc(FILE *fh);
+char *fgets(char *str, int size, FILE *fh);
+
 #endif /* __STDIO_H__ */
 
diff --git a/include/syscall.h b/include/syscall.h
index 973d9ee..afbbd36 100644
--- a/include/syscall.h
+++ b/include/syscall.h
@@ -13,9 +13,10 @@ int SystemMemProtect(void *addr, uint64_t len, int flags);
 
 // IO
 int SystemRead(uint64_t fd, void *addr, uint64_t off, uint64_t length);
-int SystemWrite(uint64_t fd, void *addr, uint64_t off, uint64_t length);
+int SystemWrite(uint64_t fd, const void *addr, uint64_t off, uint64_t length);
 int SystemFlush(uint64_t fd);
 uint64_t SystemOpen(const char *path, uint64_t flags);
+int SystemClose(uint64_t fd);
 
 #endif /* __SYSCALL_H__ */
 
diff --git a/include/unistd.h b/include/unistd.h
index d608ad4..37c2a54 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -2,6 +2,10 @@
 #ifndef __UNISTD_H__
 #define __UNISTD_H__
 
+#define STDIN_FILENO		0
+#define STDOUT_FILENO		1
+#define STDERR_FILENO		2
+
 int syscall(int number, ...);
 
 #endif /* __UNISTD_H__ */
diff --git a/lib/libc/SConscript b/lib/libc/SConscript
index f934b53..809cd99 100644
--- a/lib/libc/SConscript
+++ b/lib/libc/SConscript
@@ -9,6 +9,7 @@ src = [ ]
 src_common = [
     "assert.c",
     "exit.c",
+    "file.c",
     "syscall.c",
     "posix/mman.c",
 ]
diff --git a/lib/libc/file.c b/lib/libc/file.c
new file mode 100644
index 0000000..a86cfd7
--- /dev/null
+++ b/lib/libc/file.c
@@ -0,0 +1,160 @@
+
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <unistd.h>
+
+#include <syscall.h>
+
+static FILE __stdin = { 1, STDIN_FILENO, 0 };
+static FILE __stdout = { 1, STDOUT_FILENO, 0 };
+static FILE __stderr = { 1, STDERR_FILENO, 0 };
+
+FILE *stdin = &__stdin;
+FILE *stdout = &__stdout;
+FILE *stderr = &__stderr;
+
+static FILE fds[FOPEN_MAX] = {
+    { 0, 0, 0 },
+    { 0, 0, 0 },
+    { 0, 0, 0 },
+    { 0, 0, 0 },
+    { 0, 0, 0 },
+    { 0, 0, 0 },
+    { 0, 0, 0 },
+    { 0, 0, 0 },
+    { 0, 0, 0 },
+    { 0, 0, 0 },
+    { 0, 0, 0 },
+    { 0, 0, 0 },
+    { 0, 0, 0 },
+    { 0, 0, 0 },
+    { 0, 0, 0 },
+    { 0, 0, 0 },
+};
+
+FILE *
+_alloc_file()
+{
+    for (int i = 0; i < FOPEN_MAX; i++) {
+	if (fds[i].in_use == 0) {
+	    fds[i].in_use = 1;
+	    return &fds[i];
+	}
+    }
+
+    // XXX: malloc
+}
+
+void
+_free_file(FILE *fh)
+{
+    fh->fd = 0;
+    fh->offset = 0;
+    fh->in_use = 0;
+
+    // XXX: free
+}
+
+FILE *
+fopen(const char *path, const char *mode)
+{
+    uint64_t fd;
+    FILE *fh;
+    // XXX: handle mode
+
+    fd = SystemOpen(path, 0);
+    if (fd == 0)
+	return NULL;
+
+    fh = _alloc_file();
+    fh->fd = fd;
+    fh->offset = 0;
+
+    // XXX: handle append
+
+    return fh;
+}
+
+int
+fclose(FILE *fh)
+{
+    int status = SystemClose(fh->fd);
+
+    _free_file(fh);
+
+    return status;
+}
+
+int
+feof(FILE *fh)
+{
+}
+
+int
+fflush(FILE *fh)
+{
+}
+
+size_t
+fread(void *buf, size_t size, size_t nmemb, FILE *fh)
+{
+    return SystemRead(fh->fd, buf, 0, size * nmemb);
+    // set errno
+}
+
+size_t
+fwrite(const void *buf, size_t size, size_t nmemb, FILE *fh)
+{
+    return SystemWrite(fh->fd, buf, 0, size * nmemb);
+    // set errno
+}
+
+int
+fputc(int ch, FILE *fh)
+{
+    if (fwrite(&ch, 1, 1, fh) == 1)
+	return ch;
+    return EOF;
+}
+
+int
+fputs(const char *str, FILE *fh)
+{
+    int status = fwrite(str, strlen(str), 1, fh);
+    if (status > 0)
+	return status;
+    // XXX: error handling
+    return EOF;
+}
+
+int
+fgetc(FILE *fh)
+{
+    char ch;
+    if (fread(&ch, 1, 1, fh) == 1)
+	return ch;
+    return EOF;
+}
+
+char *
+fgets(char *str, int size, FILE *fh)
+{
+    int i;
+
+    for (i = 0; i < (size - 1); i++) {
+	int ch = fgetc(fh);
+	if (ch == EOF)
+	    return NULL;
+	str[i] = (char)ch;
+	if (ch == '\n') {
+	    str[i + 1] = '\0';
+	    return str;
+	}
+    }
+
+    str[size - 1] = '\0';
+    return str;
+}
+
diff --git a/lib/libc/syscall.c b/lib/libc/syscall.c
index af4fa24..a39c097 100644
--- a/lib/libc/syscall.c
+++ b/lib/libc/syscall.c
@@ -50,7 +50,7 @@ SystemRead(uint64_t fd, void *addr, uint64_t off, uint64_t length)
 }
 
 int
-SystemWrite(uint64_t fd, void *addr, uint64_t off, uint64_t length)
+SystemWrite(uint64_t fd, const void *addr, uint64_t off, uint64_t length)
 {
     return syscall(SYSCALL_WRITE, fd, addr, off, length);
 }
@@ -67,3 +67,9 @@ SystemOpen(const char *path, uint64_t flags)
     return syscall(SYSCALL_OPEN, path, flags);
 }
 
+int
+SystemClose(uint64_t fd)
+{
+    return syscall(SYSCALL_CLOSE, fd);
+}
+
diff --git a/sys/include/types.h b/sys/include/types.h
index d7b226a..61b1703 100644
--- a/sys/include/types.h
+++ b/sys/include/types.h
@@ -18,6 +18,9 @@ typedef uint64_t size_t;
 typedef int64_t ssize_t;
 
 typedef int64_t off_t;
+typedef int64_t fpos_t;
+
+#define NULL ((void *)0)
 
 #endif /* __SYS_TYPES_H__ */