diff --git a/zig/system.zig b/zig/system.zig
new file mode 100644
index 0000000..2067c26
--- /dev/null
+++ b/zig/system.zig
@@ -0,0 +1,162 @@
+const std = @import("std");
+
+pub fn add_defines(b: *std.Build, compile_step: *std.build.Step.Compile) {
+  const target = b.standardTargetOptions(.{});
+  const t = target.result;
+
+  // define size of pointer
+  var is64Bits = true;
+  var is32Bits = false;
+
+  switch (t.cpu.arch) {
+    .x86 => {
+      is32Bits = true;
+      is64Bits = false;
+    },
+
+    .x86_64 => {
+      is32Bits = false;
+      is64Bits = true;
+    }
+  }
+
+  if (is64Bits) {
+    compile_step.defineCMacro("WHOA_ARCH_64", "1");
+  }
+
+  if (is32Bits) {
+    compile_step.defineCMacro("WHOA_ARCH_32", "1");
+  }
+
+  // define operating system
+  var isDarwin = false;
+  var isLinux = false;
+  var isWindows = false;
+
+  switch (t.os.tag) {
+    .windows => {
+      isWindows = true;
+    },
+
+    .macos => {
+      isDarwin = true;
+    },
+
+    .linux => {
+      isLinux = true;
+    }
+  }
+
+  if (isWindows) {
+    compile_step.defineCMacro("WHOA_SYSTEM_WIN", "1");
+  }
+
+  if (isDarwin) {
+    compile_step.defineCMacro("WHOA_SYSTEM_MAC", "1");
+  }
+
+  if (isLinux) {
+    compile_step.defineCMacro("WHOA_SYSTEM_LINUX", "1");
+  }
+
+  // define operating system version
+
+  const WHOA_WIN_UNK = "9999";
+  const WHOA_WIN_XP = "510";
+  const WHOA_WIN_VISTA = "600";
+  const WHOA_WIN_7 = "610";
+  const WHOA_WIN_8 = "620";
+  const WHOA_WIN_8_1 = "630";
+  const WHOA_WIN_10 = "1000";
+  const WHOA_MAC_UNK = "9999";
+  const WHOA_MAC_10_8 = "1008";
+  const WHOA_MAC_10_9 = "1009";
+  const WHOA_MAC_10_10 = "1010";
+  const WHOA_MAC_10_11 = "1011";
+  const WHOA_MAC_10_12 = "1012";
+  const WHOA_MAC_10_13 = "1013";
+  const WHOA_MAC_10_14 = "1014";
+  const WHOA_MAC_10_15 = "1015";
+  const WHOA_MAC_11_0 = "1100";
+  const WHOA_LINUX_UNK = "9999";
+
+  var system_version = "9999";
+
+  if (isWindows) {
+    switch (t.os.semver.min.major) {
+      5 => {
+        system_version = WHOA_WIN_XP;
+      },
+
+      6 => {
+        system_version = WHOA_WIN_VISTA;
+      },
+
+      7 => {
+        system_version = WHOA_WIN_7;
+      },
+
+      8 => {
+        system_version = WHOA_WIN_8;
+
+        if (t.os.semver.min.minor == 1) {
+          system_version = WHOA_WIN_8_1;
+        }
+      },
+
+      10 => {
+        system_version = WHOA_WIN_10;
+      }
+    }
+  } else if (isDarwin) {
+    system_version = WHOA_MAC_UNK;
+
+    switch (t.os.semver.min.major) {
+      10 => {
+        system_version = WHOA_MAC_10_8;
+
+        switch (t.os.semver.min.minor) {
+          8 => {
+            system_version = WHOA_MAC_10_8;
+          },
+
+          9 => {
+            system_version = WHOA_MAC_10_9;
+          },
+
+          10 => {
+            system_version = WHOA_MAC_10_10;
+          },
+
+          11 => {
+            system_version = WHOA_MAC_10_11;
+          },
+
+          12 => {
+            system_version = WHOA_MAC_10_12;
+          },
+
+          13 => {
+            system_version = WHOA_MAC_10_13;
+          },
+
+          14 => {
+            system_version = WHOA_MAC_10_14;
+          },
+
+          15 => {
+            system_version = WHOA_MAC_10_15;
+          }
+        }
+      },
+
+      11 => {
+        system_version = WHOA_MAC_11_0;
+      }
+    }
+  } else if (isLinux) {
+    system_version = WHOA_LINUX_UNK;
+  }
+
+  compile_step.defineCMacro("WHOA_SYSTEM_VERSION", system_version);
+}