diff --git a/code/os/win/win_env.c b/code/os/win/win_env.c
index 6154ea7..f72b20e 100644
--- a/code/os/win/win_env.c
+++ b/code/os/win/win_env.c
@@ -3,7 +3,7 @@
 
 #include "win.h"
 
-char* getenv(const char *name) {
+char *getenv(const char *name) {
     // The string pointed to shall not be modified by the program, but may be
     // overwritten by a subsequent call to the getenv function
     static size_t env_string_cap;
diff --git a/code/os/win/win_io.c b/code/os/win/win_io.c
index 49d0834..c887e7c 100644
--- a/code/os/win/win_io.c
+++ b/code/os/win/win_io.c
@@ -3,6 +3,8 @@
 
 #include <stddef.h>
 #include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
 
 // It's just mapped directly to HANDLE
 struct FILE {
@@ -57,14 +59,14 @@ FILE *_os_fopen(char const *restrict name, _OS_ModeFlags flags) {
     }
 
     HANDLE fileHandle = CreateFileA(
-        name,
-        desaddr,
-        share,
-        NULL,
-        disp,
-        FILE_ATTRIBUTE_NORMAL,
-        NULL
-    );
+                                    name,
+                                    desaddr,
+                                    share,
+                                    NULL,
+                                    disp,
+                                    FILE_ATTRIBUTE_NORMAL,
+                                    NULL
+                                    );
     FILE *file = (FILE *)fileHandle;
     if(fileHandle == INVALID_HANDLE_VALUE) {
         file = NULL;
@@ -83,3 +85,45 @@ void _os_file_write(void* ctx, size_t n, const char str[]) {
     DWORD written = 0;
     WriteFile((HANDLE) ctx, str, n, &written, NULL);
 }
+
+int system(const char* string) {
+    int wchars_required = MultiByteToWideChar(65001 /* UTF8 */, 0, string, -1, NULL, 0);
+    wchar_t* cmd_line = malloc(sizeof(L"cmd.exe ") + (wchars_required * sizeof(wchar_t)));
+    if (cmd_line == NULL) {
+        goto error;
+    }
+
+    memcpy(cmd_line, L"cmd.exe ", sizeof(L"cmd.exe "));
+    MultiByteToWideChar(65001 /* UTF8 */, 0, string, -1, cmd_line + sizeof("cmd.exe ") - 1, wchars_required);
+
+    STARTUPINFOW si = {
+		.cb = sizeof(STARTUPINFOW),
+		.dwFlags = STARTF_USESTDHANDLES,
+		.hStdInput = GetStdHandle(STD_INPUT_HANDLE),
+		.hStdError = GetStdHandle(STD_ERROR_HANDLE),
+		.hStdOutput = GetStdHandle(STD_OUTPUT_HANDLE)
+	};
+	PROCESS_INFORMATION pi = {};
+
+    if (!CreateProcessW(NULL, cmd_line, NULL, NULL, TRUE, 0, NULL, NULL, &si, &pi)) {
+        goto error;
+    }
+
+	// Wait until child process exits.
+	WaitForSingleObject(pi.hProcess, INFINITE);
+
+    DWORD exit_code;
+    if (!GetExitCodeProcess(pi.hProcess, &exit_code)) {
+        goto error;
+    }
+
+	// Close process and thread handles.
+	CloseHandle(pi.hProcess);
+	CloseHandle(pi.hThread);
+    free(cmd_line);
+    return exit_code;
+
+    error:
+    free(cmd_line);
+    return -1;
+}
diff --git a/inc/math.h b/inc/math.h
index 244aee2..3326e0c 100644
--- a/inc/math.h
+++ b/inc/math.h
@@ -5,7 +5,7 @@ typedef float float_t;
 typedef double double_t;
 
 #ifndef _HUGE_ENUF
-    #define _HUGE_ENUF  1e+300  // _HUGE_ENUF*_HUGE_ENUF must overflow
+#define _HUGE_ENUF  1e+300  // _HUGE_ENUF*_HUGE_ENUF must overflow
 #endif
 
 #define INFINITY   ((float)(_HUGE_ENUF * _HUGE_ENUF))
@@ -27,10 +27,9 @@ typedef double double_t;
 #define FP_NORMAL    2
 #define FP_SUBNORMAL 3
 #define FP_ZERO      4
-#define fpclassify(x) ( \
-    _is_float(x)  ? _fpclassify_f(x) :
-    _is_double(x) ? _fpclassify_d(x) :
-    FP_NAN)
+
+#define fpclassify(x) 0
+#define isfinite(x) 0
 
 double acos(double x);
 float acosf(float x);
diff --git a/inc/stdlib.h b/inc/stdlib.h
index ae9c2fa..672cfbd 100644
--- a/inc/stdlib.h
+++ b/inc/stdlib.h
@@ -70,7 +70,7 @@ _Noreturn void exit(int status);
 _Noreturn void _Exit(int status);
 char *getenv(const char *name);
 // _Noreturn void quick_exit(int status);
-// int system(const char *string);
+int system(const char *string);
 const void *bsearch(const void *key, const void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *));
 // void qsort(void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *));
 // int abs(int j);
diff --git a/test/test4.c b/test/test4.c
index 29c4f09..da1cb51 100644
--- a/test/test4.c
+++ b/test/test4.c
@@ -22,6 +22,8 @@ int data_cmp(void const *lhs, void const *rhs)
 
 int main(void)
 {
+    system("clang -v");
+
     struct data key = { .nr = 3 };
     struct data const *res = bsearch(&key, dat, sizeof dat / sizeof dat[0], sizeof dat[0], data_cmp);
     if (res) {