diff --git a/src/main.zig b/src/main.zig
index 5a7883e..6ae442b 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -1,6 +1,7 @@
 const std = @import("std");
 
 const Uxn = @import("uxn.zig");
+const Varvara = @import("varvara.zig");
 // TODO combine with uxn.zig
 const UxnFmt = @import("uxn-instructions.zig");
 
@@ -20,13 +21,16 @@ pub fn main() !void {
         const rom = try file.readToEndAlloc(allocator, 0xFF00);
         defer allocator.free(rom);
 
-        var uxn = Uxn{ .pc = 0x100 };
-        @memcpy(uxn.mem.m[0x100 .. rom.len + 0x100], rom);
+        var varvara = Varvara.init(rom);
 
         var running = true;
         while (running) {
-            std.debug.print("pc={X} code={X} op={s}\n", .{ uxn.pc, uxn.mem.m[uxn.pc], UxnFmt.fmtInstrs(uxn.mem.m[uxn.pc .. uxn.pc +% 1]) });
-            if (uxn.eval()) running = false;
+            std.debug.print("pc={X} code={X} op={s}\n", .{
+                varvara.uxn.pc,
+                varvara.uxn.mem.m[varvara.uxn.pc],
+                UxnFmt.fmtInstrs(varvara.uxn.mem.m[varvara.uxn.pc .. varvara.uxn.pc +% 1]),
+            });
+            if (varvara.uxn.eval()) running = false;
         }
     } else return error.NoRom;
 }
diff --git a/src/uxn.zig b/src/uxn.zig
index 1da3114..d88cc3a 100644
--- a/src/uxn.zig
+++ b/src/uxn.zig
@@ -7,6 +7,16 @@ rs: Stack = .{ .s = undefined },
 dev: [0x100]u8 = undefined,
 pc: u16,
 
+deo8: *const fn (*Uxn, *Stack, u8, u8) void = deo8Stub,
+deo16: *const fn (*Uxn, *Stack, u8, u16) void = deo16Stub,
+dei8: *const fn (*Uxn, *Stack, u8) void = dei8Stub,
+dei16: *const fn (*Uxn, *Stack, u8) void = dei16Stub,
+
+fn deo8Stub(_: *Uxn, _: *Stack, _: u8, _: u8) void {}
+fn deo16Stub(_: *Uxn, _: *Stack, _: u8, _: u16) void {}
+fn dei8Stub(_: *Uxn, _: *Stack, _: u8) void {}
+fn dei16Stub(_: *Uxn, _: *Stack, _: u8) void {}
+
 const Memory = struct {
     m: [0x10000]u8,
 
@@ -503,21 +513,29 @@ fn sta(self: *Uxn, stack: *Stack, comptime T: type, comptime keep: bool) void {
 
 fn dei(self: *Uxn, stack: *Stack, comptime T: type, comptime keep: bool) void {
     const d = if (keep) stack.peek(u8) else stack.pop(u8);
+    switch (T) {
+        u8 => self.dei8(self, stack, d),
+        u16 => self.dei16(self, stack, d),
+        else => @compileError("expected u8 or u16, got " + @typeName(T)),
+    }
     stack.push(T, self.dev[d]);
 }
 
 fn deo(self: *Uxn, stack: *Stack, comptime T: type, comptime keep: bool) void {
-    std.debug.print("DEO: {any} ", .{stack.s});
     const d = if (keep) stack.peek(u8) else stack.pop(u8);
     const v = if (keep) stack.peek(T) else stack.pop(T);
-    std.debug.print("v{X} d{X}\n", .{ v, d });
+    std.debug.print("DEO: dev {X}, val {X}\n", .{ d, v });
     switch (T) {
-        u8 => self.dev[d] = v,
+        u8 => {
+            self.dev[d] = v;
+            self.deo8(self, stack, d, v);
+        },
         u16 => {
             self.dev[d] = @truncate(v >> 8);
             self.dev[d +% 1] = @truncate(v & 0xFF);
+            self.deo16(self, stack, d, v);
         },
-        else => unreachable,
+        else => @compileError("expected u8 or u16, got " + @typeName(T)),
     }
 }
 
diff --git a/src/varvara.zig b/src/varvara.zig
new file mode 100644
index 0000000..60110b9
--- /dev/null
+++ b/src/varvara.zig
@@ -0,0 +1,40 @@
+const std = @import("std");
+
+const Uxn = @import("uxn.zig");
+const Varvara = @This();
+
+uxn: Uxn,
+
+pub fn init(rom: []const u8) Varvara {
+    var uxn = Uxn{ .pc = 0x100 };
+    @memcpy(uxn.mem.m[0x100 .. rom.len + 0x100], rom);
+    return .{ .uxn = uxn };
+}
+
+pub fn deo8(uxn: *Uxn, stack: *Uxn.Stack, device: u8, value: u8) void {
+    const self: Varvara = @fieldParentPtr("uxn", uxn);
+    // _ = .{ self, stack, device, value };
+    _ = self;
+    _ = stack;
+    switch (device) {
+        0x18 => {
+            std.io.getStdOut().writer().writeByte(value) catch |e| @panic(e);
+        },
+        else => {},
+    }
+}
+
+pub fn deo16(uxn: *Uxn, stack: *Uxn.Stack, device: u8, value: u16) void {
+    const self: Varvara = @fieldParentPtr("uxn", uxn);
+    _ = .{ self, stack, device, value };
+}
+
+pub fn dei8(uxn: *Uxn, stack: *Uxn.Stack, device: u8, value: u8) void {
+    const self: Varvara = @fieldParentPtr("uxn", uxn);
+    _ = .{ self, stack, device, value };
+}
+
+pub fn dei16(uxn: *Uxn, stack: *Uxn.Stack, device: u8, value: u16) void {
+    const self: Varvara = @fieldParentPtr("uxn", uxn);
+    _ = .{ self, stack, device, value };
+}