diff --git a/Makefile b/Makefile
index c54650f..5909eba 100644
--- a/Makefile
+++ b/Makefile
@@ -10,11 +10,18 @@ CXXFLAGS += $(shell pkgconf sdl2 --libs)
 build_dir = build
 obj_dir = $(build_dir)/obj
 
-sources := $(shell find src/ -name *.cpp)
+sources := $(shell find src/ -name *.cpp -and -not -name *main.cpp)
 
-all: $(build_dir)/vc5
+vc5_sources := $(sources) src/main.cpp
+asm_sources := $(sources) src/asm_main.cpp
 
-$(build_dir)/vc5: $(sources:%.cpp=$(obj_dir)/%.o)
+all: $(build_dir)/vc5 $(build_dir)/asm
+
+$(build_dir)/vc5: $(vc5_sources:%.cpp=$(obj_dir)/%.o)
+	@mkdir -p $(dir $@)
+	g++ $^ -o $@ $(CXXFLAGS) $(LDFLAGS)
+
+$(build_dir)/asm: $(asm_sources:%.cpp=$(obj_dir)/%.o)
 	@mkdir -p $(dir $@)
 	g++ $^ -o $@ $(CXXFLAGS) $(LDFLAGS)
 
diff --git a/programs/boot.vc5asm b/programs/boot.vc5asm
new file mode 100644
index 0000000..0d4f51b
--- /dev/null
+++ b/programs/boot.vc5asm
@@ -0,0 +1,87 @@
+
+
+const KBD_STATUS 0x1ffc
+const KBD_CODE 0x1ffe
+const VCD 0x2000
+
+const FL_EQ 0x2
+const FL_EQ 0x4
+
+const KBD_FLAG_IS_RELEASE 0x1
+
+    mov rsp, 0x1000
+    mov rbp, rsp
+
+    mov r0, 512
+    mov r1, 1
+    dskr r0, r1
+
+    ; setup video character display (VCD)
+    ; descriptor table structure:
+    ;   [addr + 0] memory map base
+    mov r0, VCD
+    mov [0x700], r0
+    lvcd 0x700
+
+    ; setup keyboard (KBD)
+    ; descriptor table structure:
+    ;   [addr + 0] status address
+    ;   [addr + 2] keycode address
+    ;   [addr + 4] keyboard interrupt handler
+    mov r0, KBD_STATUS
+    mov [0x702], r0
+    mov r0, KBD_CODE
+    mov [0x704], r0
+    mov r0, key_press_int
+    mov [0x706], r0
+    lkbd 0x702
+
+    ; character counter
+    mov r0, 0
+    mov [0x600], r0
+
+main_loop:
+    hlt
+    jmp main_loop
+    
+key_press_int:
+    mov r0, [KBD_STATUS]
+    and r0, r0, KBD_FLAG_IS_RELEASE
+    jnz r0, .leave
+
+    mov r0, [0x600]
+    add r0, r0, VCD
+    mov r1, [KBC_CODE]
+    cmp r1, 44 ; spacebar
+    mov r2, rfl
+    and r2, r2, FL_EQ
+    jnz r2, .incr
+    add r1, r1, 61
+    mov byte [r0], r1
+.incr:
+    mov r0, [0x600]
+    add r0, r0, 1
+    mov [0x600], r0
+.leave:
+    reti
+
+;scancode_to_char:
+;    cmp r1, 61
+;
+;    mov r2, rfl
+;    and r2, r2, FL_LT
+;    jnz .not_letter
+;
+;    ; if r1 > 86 { goto .not_letter }
+;    cmp r1, 86
+;    mov r2, rfl
+;    xor r2, 0xffff
+;    and r2, r2, FL_EQ | FL_LT
+;
+;
+;    mov r4, rfl
+;    and r4, r4, FL_EQ
+;    shr r4, r4, 2
+
+
+
diff --git a/src/asm_main.cpp b/src/asm_main.cpp
new file mode 100644
index 0000000..09eb4f6
--- /dev/null
+++ b/src/asm_main.cpp
@@ -0,0 +1,58 @@
+#include "assembler.hpp"
+#include <cstdio>
+#include <cstdlib>
+#include <filesystem>
+#include <print>
+#include <string_view>
+
+using namespace std::literals;
+namespace fs = std::filesystem;
+
+int main(int argc, char** argv)
+{
+    auto input_filename = std::string_view();
+    auto output_filename = std::string_view();
+
+    int i = 0;
+    while (i < argc) {
+        auto arg = std::string_view(argv[i]);
+        if (arg == "--help") {
+            std::println("asm <input file> -o <output file>");
+            return EXIT_SUCCESS;
+        } else if (arg == "-o") {
+            i += 1;
+            if (i >= argc) {
+                std::println(stderr, "error: expected filename after -o");
+                return EXIT_FAILURE;
+            }
+            output_filename = argv[i];
+            i += 1;
+        } else if (arg.starts_with("-")) {
+            std::println(stderr, "error: unknown flag \"{}\"", arg);
+            return EXIT_FAILURE;
+        } else {
+            input_filename = argv[i];
+            i += 1;
+        }
+    }
+
+    if (input_filename.empty()) {
+        std::println(stderr, "error: no input file specified");
+        return EXIT_FAILURE;
+    }
+
+    auto input_path = fs::path(input_filename);
+    auto output_path = fs::path(output_filename);
+
+    if (output_path.empty()) {
+        output_path = input_path;
+        output_path.replace_extension("o");
+    }
+
+    auto result = vc5::tools::assemble_file(input_path, output_path);
+
+    if (not result) {
+        std::println(stderr, "error: {}", result.error());
+        return EXIT_FAILURE;
+    }
+}
diff --git a/src/assembler.cpp b/src/assembler.cpp
index 4d0c91e..9691be3 100644
--- a/src/assembler.cpp
+++ b/src/assembler.cpp
@@ -11,6 +11,7 @@
 #include <fstream>
 #include <ios>
 #include <memory>
+#include <print>
 #include <string_view>
 #include <unordered_map>
 #include <utility>
@@ -48,9 +49,14 @@ auto vc5::tools::assemble_file(fs::path input_path, fs::path output_path)
         input_file.read(&text[0], size);
     }
 
-    auto assembler = Assembler(text);
+    auto input_filename = std::string(input_path);
+
+    auto assembler = Assembler(input_filename, text);
     auto result = assembler.assemble_file();
 
+    if (not result)
+        return std::unexpected(result.error());
+
     auto& program = *result;
 
     {
@@ -72,15 +78,20 @@ auto vc5::tools::assemble_file(fs::path input_path, fs::path output_path)
 auto Assembler::assemble_file()
     -> std::expected<std::vector<uint8_t>, std::string>
 {
-    auto parser = Parser(m_text);
+    auto parser = Parser(m_filename, m_text);
     auto lines = std::vector<std::unique_ptr<Line>>();
 
     while (true) {
+        parser.eat_whitespace();
+        if (parser.is_done()) {
+            break;
+        }
 
         if (parser.next_is_const()) {
             auto stmt = parser.parse_const();
             if (not stmt) {
-                return std::unexpected("parsing failed");
+                parser.try_recover();
+                continue;
             }
 
             auto value = eval_operand_to_imm(*stmt->expr);
@@ -94,7 +105,8 @@ auto Assembler::assemble_file()
         } else if (parser.next_is_align()) {
             auto stmt = parser.parse_align();
             if (not stmt) {
-                return std::unexpected("parsing failed");
+                parser.try_recover();
+                continue;
             }
 
             auto value = eval_operand_to_imm(*stmt->expr);
@@ -132,10 +144,14 @@ auto Assembler::assemble_file()
                 stmt->loc, nullptr, "db", std::move(ops)));
 
         } else {
-
             auto line = parser.parse_line();
             if (not line) {
-                break;
+                if (parser.is_done()) {
+                    break;
+                }
+
+                parser.try_recover();
+                continue;
             }
             lines.push_back(std::move(line));
         }
@@ -148,6 +164,19 @@ auto Assembler::assemble_file()
     m_builder.set_ip(0);
     m_second_pass = true;
 
+    for (const auto& line : lines) {
+        std::println("[{}] = {}", m_builder.ip(), line->ident);
+        assemble_line(*line);
+    }
+
+    for (size_t i = 0; i < 64; i += 4) {
+        std::println("{:02x} {:02x} {:02x} {:02x}",
+            m_program[i],
+            m_program[i + 1],
+            m_program[i + 2],
+            m_program[i + 3]);
+    }
+
     return std::move(m_program);
 }
 
@@ -187,8 +216,8 @@ static const auto mnemonic_map
           { "nop", M::nop },      { "hlt", M::hlt },
           { "jmp", M::jmp },      { "jnz", M::jnz },
           { "mov", M::mov },      { "cmp", M::cmp },
-          { "or_", M::or_ },      { "and_", M::and_ },
-          { "xor_", M::xor_ },    { "shl", M::shl },
+          { "or", M::or_ },      { "and", M::and_ },
+          { "xor", M::xor_ },    { "shl", M::shl },
           { "rshl", M::rshl },    { "shr", M::shr },
           { "rshr", M::rshr },    { "add", M::add },
           { "sub", M::sub },      { "rsub", M::rsub },
@@ -204,13 +233,13 @@ void Assembler::assemble_line(const Line& line)
 {
     auto loc = line.loc;
 
-    constexpr auto Reg = EOT::Reg;
-    constexpr auto Imm = EOT::Imm;
-    constexpr auto Str = EOT::Str;
-    constexpr auto MemByteImm = EOT::MemByteImm;
-    constexpr auto MemByteReg = EOT::MemByteReg;
-    constexpr auto MemWordImm = EOT::MemWordImm;
-    constexpr auto MemWordReg = EOT::MemWordReg;
+    [[maybe_unused]] constexpr auto Reg = EOT::Reg;
+    [[maybe_unused]] constexpr auto Imm = EOT::Imm;
+    [[maybe_unused]] constexpr auto Str = EOT::Str;
+    [[maybe_unused]] constexpr auto MemByteImm = EOT::MemByteImm;
+    [[maybe_unused]] constexpr auto MemByteReg = EOT::MemByteReg;
+    [[maybe_unused]] constexpr auto MemWordImm = EOT::MemWordImm;
+    [[maybe_unused]] constexpr auto MemWordReg = EOT::MemWordReg;
 
     auto& l = m_builder;
 
@@ -269,6 +298,9 @@ void Assembler::assemble_line(const Line& line)
             if (arg_count_wrong(line, 1))
                 return;
             auto op = eval_operand(*line.args[0]);
+            if (not op)
+                return;
+
             if (op->is_reg()) {
                 l.jmp_reg(op->as_reg());
             } else if (op->is_imm()) {
@@ -279,10 +311,14 @@ void Assembler::assemble_line(const Line& line)
             break;
         }
         case M::jnz: {
-            if (arg_count_wrong(line, 1))
+            if (arg_count_wrong(line, 2))
                 return;
             auto op1 = eval_operand(*line.args[0]);
             auto op2 = eval_operand(*line.args[1]);
+
+            if (not op1 or op2)
+                return;
+
             if (not op1->is_reg())
                 operation_not_supported();
             if (op2->is_reg()) {
@@ -300,6 +336,9 @@ void Assembler::assemble_line(const Line& line)
             auto dst = eval_operand(*line.args[0]);
             auto src = eval_operand(*line.args[1]);
 
+            if (not dst or src)
+                return;
+
             auto dst_ty = dst->ty;
             auto src_ty = src->ty;
 
@@ -338,14 +377,19 @@ void Assembler::assemble_line(const Line& line)
             auto op1 = eval_operand(*line.args[0]);
             auto op2 = eval_operand(*line.args[1]);
 
+            if (not op1 or not op2)
+                return;
+
+            if (not op1->is_reg())
+                operation_not_supported();
+
             if (op2->is_reg()) {
-
+                l.cmp_reg(op1->as_reg(), op2->as_reg());
             } else if (op2->is_imm()) {
-
+                l.cmp_imm(op1->as_reg(), op2->as_imm());
             } else {
                 operation_not_supported();
             }
-
             break;
         }
         case M::or_:
@@ -357,13 +401,168 @@ void Assembler::assemble_line(const Line& line)
         case M::rshr:
         case M::add:
         case M::sub:
-        case M::rsub:
-        case M::reti:
-        case M::lvcd:
-        case M::lkbd:
-        case M::dskr:
-        case M::dskw:
+        case M::rsub: {
+            if (arg_count_wrong(line, 3))
+                return;
+            auto dst = eval_operand(*line.args[0]);
+            auto op1 = eval_operand(*line.args[1]);
+            auto op2 = eval_operand(*line.args[2]);
+
+            if (not dst or not op1 or not op2)
+                return;
+
+            if (not dst->is_reg())
+                operation_not_supported();
+            if (not op1->is_reg())
+                operation_not_supported();
+
+            if (op2->is_reg()) {
+                switch (m) {
+                    case Mnemonic::or_:
+                        l.or_reg(dst->as_reg(), op1->as_reg(), op2->as_reg());
+                        break;
+                    case Mnemonic::and_:
+                        l.and_reg(dst->as_reg(), op1->as_reg(), op2->as_reg());
+                        break;
+                    case Mnemonic::xor_:
+                        l.xor_reg(dst->as_reg(), op1->as_reg(), op2->as_reg());
+                        break;
+                    case Mnemonic::shl:
+                        l.shl_reg(dst->as_reg(), op1->as_reg(), op2->as_reg());
+                        break;
+                    case Mnemonic::rshl:
+                        l.rshl_reg(dst->as_reg(), op1->as_reg(), op2->as_reg());
+                        break;
+                    case Mnemonic::shr:
+                        l.shr_reg(dst->as_reg(), op1->as_reg(), op2->as_reg());
+                        break;
+                    case Mnemonic::rshr:
+                        l.rshr_reg(dst->as_reg(), op1->as_reg(), op2->as_reg());
+                        break;
+                    case Mnemonic::add:
+                        l.add_reg(dst->as_reg(), op1->as_reg(), op2->as_reg());
+                        break;
+                    case Mnemonic::sub:
+                        l.sub_reg(dst->as_reg(), op1->as_reg(), op2->as_reg());
+                        break;
+                    case Mnemonic::rsub:
+                        l.rsub_reg(dst->as_reg(), op1->as_reg(), op2->as_reg());
+                        break;
+                    default:
+                        assert(false && "unhandled");
+                }
+            } else if (op2->is_imm()) {
+                switch (m) {
+                    case Mnemonic::or_:
+                        l.or_imm(dst->as_reg(), op1->as_reg(), op2->as_imm());
+                        break;
+                    case Mnemonic::and_:
+                        l.and_imm(dst->as_reg(), op1->as_reg(), op2->as_imm());
+                        break;
+                    case Mnemonic::xor_:
+                        l.xor_imm(dst->as_reg(), op1->as_reg(), op2->as_imm());
+                        break;
+                    case Mnemonic::shl:
+                        l.shl_imm(dst->as_reg(), op1->as_reg(), op2->as_imm());
+                        break;
+                    case Mnemonic::rshl:
+                        l.rshl_imm(dst->as_reg(), op1->as_reg(), op2->as_imm());
+                        break;
+                    case Mnemonic::shr:
+                        l.shr_imm(dst->as_reg(), op1->as_reg(), op2->as_imm());
+                        break;
+                    case Mnemonic::rshr:
+                        l.rshr_imm(dst->as_reg(), op1->as_reg(), op2->as_imm());
+                        break;
+                    case Mnemonic::add:
+                        l.add_imm(dst->as_reg(), op1->as_reg(), op2->as_imm());
+                        break;
+                    case Mnemonic::sub:
+                        l.sub_imm(dst->as_reg(), op1->as_reg(), op2->as_imm());
+                        break;
+                    case Mnemonic::rsub:
+                        l.rsub_imm(dst->as_reg(), op1->as_reg(), op2->as_imm());
+                        break;
+                    default:
+                        assert(false && "unhandled");
+                }
+            } else {
+                operation_not_supported();
+            }
             break;
+        }
+        case M::reti: {
+            if (arg_count_wrong(line, 0))
+                return;
+            l.reti();
+            break;
+        }
+        case M::lvcd: {
+            if (arg_count_wrong(line, 1))
+                return;
+
+            auto op1 = eval_operand(*line.args[0]);
+            if (not op1)
+                return;
+
+            if (op1->is_reg()) {
+                l.lvcd_reg(op1->as_reg());
+            } else if (op1->is_imm()) {
+                l.lvcd_imm(op1->as_imm());
+            } else {
+                operation_not_supported();
+            }
+            break;
+        }
+        case M::lkbd: {
+            if (arg_count_wrong(line, 1))
+                return;
+
+            auto op1 = eval_operand(*line.args[0]);
+            if (not op1)
+                return;
+
+            if (op1->is_reg()) {
+                l.lkbd_reg(op1->as_reg());
+            } else if (op1->is_imm()) {
+                l.lkbd_imm(op1->as_imm());
+            } else {
+                operation_not_supported();
+            }
+            break;
+        }
+        case M::dskr: {
+            if (arg_count_wrong(line, 2))
+                return;
+
+            auto dst = eval_operand(*line.args[0]);
+            auto op1 = eval_operand(*line.args[1]);
+
+            if (not dst or not op1)
+                return;
+
+            if (not dst->is_reg() or not op1->is_reg())
+                operation_not_supported();
+
+            l.dskr(dst->as_reg(), op1->as_reg());
+            break;
+        }
+        case M::dskw: {
+            if (arg_count_wrong(line, 2))
+                return;
+
+            auto dst = eval_operand(*line.args[0]);
+            auto op1 = eval_operand(*line.args[1]);
+
+            if (not dst or not op1)
+                return;
+
+            if (not dst->is_reg() or not op1->is_reg())
+                operation_not_supported();
+
+            l.dskw(dst->as_reg(), op1->as_reg());
+            break;
+        }
     }
 }
 
@@ -403,8 +602,9 @@ auto Assembler::eval_operand(const Expr& expr) -> std::unique_ptr<EvaledOperand>
         case Expr::Ty::Shl:
         case Expr::Ty::Shr:
         case Expr::Ty::Add:
-        case Expr::Ty::Sub:
-            break;
+        case Expr::Ty::Sub: {
+            return eval_operand_to_imm(expr);
+        }
     }
     assert(false && "unexhaustive");
 }
@@ -535,6 +735,7 @@ auto Assembler::eval_operand_to_imm(const Expr& expr)
         }
         case Expr::Ty::Reg:
             error(loc, "registers cannot be part of an expression");
+            return nullptr;
         case Expr::Ty::Int:
             return std::make_unique<EO>(
                 expr.loc, EOT::Imm, static_cast<uint16_t>(expr.as_int()));
@@ -574,10 +775,9 @@ auto Assembler::eval_operand_to_imm(const Expr& expr)
             return std::make_unique<EO>(loc,
                 EOT::Imm,
                 binary_op(expr.ty, left->as_imm(), right->as_imm()));
-            break;
         }
     }
-    assert(false && "unexhaustive");
+    assert(false);
 }
 
 auto Assembler::binary_op(Expr::Ty exprTy, uint16_t left, uint16_t right)
@@ -608,7 +808,7 @@ auto Assembler::binary_op(Expr::Ty exprTy, uint16_t left, uint16_t right)
             //     return (uint16_t)((int16_t)left % (int16_t)right);
 
         default:
-            assert(false && "unexhaustive");
+            assert(false && "unhandled");
     }
 }
 
@@ -616,15 +816,32 @@ bool Assembler::arg_count_wrong(const Line& ins, size_t count)
 {
     if (ins.args.size() != count) {
         error(ins.loc, std::format("expected {} operands", count));
-        return false;
+        return true;
     }
-    return true;
+    return false;
 }
 
 void Assembler::error(Loc loc, std::string_view message)
 {
     m_failed = true;
-    loc.print_error(m_text, message);
+    loc.print_error(m_text, message, m_filename);
+}
+
+void Parser::eat_whitespace()
+{
+    while (eat('\n')) { }
+}
+
+void Parser::try_recover()
+{
+    while (not test(TT::Eof) and not test('\n')) {
+        step();
+    }
+}
+
+auto Parser::is_done() const -> bool
+{
+    return test(TT::Eof);
 }
 
 auto Parser::next_is_const() const -> bool
@@ -636,6 +853,7 @@ auto Parser::parse_const() -> std::unique_ptr<Const>
 {
     assert(test(TT::KwConst));
     auto loc = m_tok.loc;
+    step();
     if (!test(TT::Ident)) {
         error(current_loc(), "expected identifier");
         return nullptr;
@@ -643,6 +861,8 @@ auto Parser::parse_const() -> std::unique_ptr<Const>
     auto ident = m_tok.text;
     step();
     auto expr = parse_expr();
+    if (not expr)
+        return nullptr;
     return std::make_unique<Const>(loc, ident, std::move(expr));
 }
 
@@ -655,6 +875,7 @@ auto Parser::parse_align() -> std::unique_ptr<Align>
 {
     assert(test(TT::KwAlign));
     auto loc = m_tok.loc;
+    step();
     if (!test(TT::Ident)) {
         error(current_loc(), "expected identifier");
         return nullptr;
@@ -662,6 +883,8 @@ auto Parser::parse_align() -> std::unique_ptr<Align>
     auto ident = m_tok.text;
     step();
     auto expr = parse_expr();
+    if (not expr)
+        return nullptr;
     return std::make_unique<Align>(loc, ident, std::move(expr));
 }
 
@@ -674,15 +897,15 @@ auto Parser::parse_line() -> std::unique_ptr<Line>
     auto ident = std::string_view();
 
     while (true) {
-        while (eat('\n')) { }
+        eat_whitespace();
 
-        if (test(TT::Ident) or eat('.')) {
+        if (test(TT::Ident) or test('.')) {
             bool is_local = false;
             if (eat('.')) {
                 is_local = true;
             }
             if (not test(TT::Ident)) {
-                error(current_loc(), "expected ident");
+                error(current_loc(), "expected identifier");
                 return nullptr;
             }
             ident = m_tok.text;
@@ -702,29 +925,39 @@ auto Parser::parse_line() -> std::unique_ptr<Line>
             labels->push_back(Label { loc, ident, is_local });
             continue;
         } else {
+            error(current_loc(), "expected identifier");
             return nullptr;
         }
     }
 
     auto args = Line::Args();
 
-    auto first = true;
-    while (not test(TT::Eof) and not eat('\n')) {
-        if (not first and not eat(',')) {
-            error(current_loc(), "expected ','");
-            return nullptr;
-        }
-        first = false;
+    if (not test(TT::Eof) and not test('\n')) {
 
         auto arg = parse_expr();
         if (not arg) {
             return nullptr;
         }
+
         args.push_back(std::move(arg));
+        while (not test(TT::Eof) and not test('\n')) {
+
+            if (not eat(',')) {
+                error(current_loc(), "expected ','");
+                return nullptr;
+            }
+
+            auto arg = parse_expr();
+            if (not arg) {
+                return nullptr;
+            }
+            args.push_back(std::move(arg));
+        }
     }
 
     if (not test(TT::Eof) and not eat('\n')) {
         error(current_loc(), "expected line ending");
+        return nullptr;
     }
 
     return std::make_unique<Line>(
@@ -790,17 +1023,17 @@ auto Parser::parse_prefix() -> std::unique_ptr<Expr>
 
 namespace {
 
-const auto reg_idents = std::unordered_map<std::string_view, vc5::Reg> {
-    { "R0", vc5::Reg::R0 },
-    { "R1", vc5::Reg::R1 },
-    { "R2", vc5::Reg::R2 },
-    { "R3", vc5::Reg::R3 },
-    { "R4", vc5::Reg::R4 },
-    { "R5", vc5::Reg::R5 },
-    { "Rbp", vc5::Reg::Rbp },
-    { "Rsp", vc5::Reg::Rsp },
-    { "Rfl", vc5::Reg::Rfl },
-    { "Rip", vc5::Reg::Rip },
+const auto reg_idents = std::unordered_map<TT, vc5::Reg> {
+    { TT::KwR0, vc5::Reg::R0 },
+    { TT::KwR1, vc5::Reg::R1 },
+    { TT::KwR2, vc5::Reg::R2 },
+    { TT::KwR3, vc5::Reg::R3 },
+    { TT::KwR4, vc5::Reg::R4 },
+    { TT::KwR5, vc5::Reg::R5 },
+    { TT::KwRbp, vc5::Reg::Rbp },
+    { TT::KwRsp, vc5::Reg::Rsp },
+    { TT::KwRfl, vc5::Reg::Rfl },
+    { TT::KwRip, vc5::Reg::Rip },
 };
 
 }
@@ -811,12 +1044,11 @@ auto Parser::parse_operand() -> std::unique_ptr<Expr>
     if (test(TT::Ident)) {
         auto ident = m_tok.text;
         step();
-        if (reg_idents.contains(ident)) {
-            return std::make_unique<Expr>(
-                loc, Expr::Ty::Reg, reg_idents.at(ident));
-        } else {
-            return std::make_unique<Expr>(loc, Expr::Ty::Ident, ident);
-        }
+        return std::make_unique<Expr>(loc, Expr::Ty::Ident, ident);
+    } else if (reg_idents.contains(m_tok.ty)) {
+        auto ty = m_tok.ty;
+        step();
+        return std::make_unique<Expr>(loc, Expr::Ty::Reg, reg_idents.at(ty));
     } else if (eat('.')) {
         if (!test(TT::Ident)) {
             error(current_loc(), "expected identifier");
@@ -824,6 +1056,7 @@ auto Parser::parse_operand() -> std::unique_ptr<Expr>
         }
         auto value
             = std::string_view(m_tok.text.data() - 1, m_tok.text.size() + 1);
+        step();
 
         return std::make_unique<Expr>(loc, Expr::Ty::SubLabel, value);
     } else if (test(TT::Int)) {
@@ -862,6 +1095,8 @@ auto Parser::parse_operand() -> std::unique_ptr<Expr>
         return std::make_unique<Expr>(loc, Expr::Ty::Str, std::move(value));
     } else if (eat('(')) {
         auto expr = parse_expr();
+        if (not expr)
+            return nullptr;
         if (not eat(')')) {
             error(current_loc(), "expected ')'");
             return nullptr;
@@ -869,30 +1104,34 @@ auto Parser::parse_operand() -> std::unique_ptr<Expr>
         return expr;
     } else if (eat('[')) {
         auto expr = parse_expr();
+        if (not expr)
+            return nullptr;
         if (not eat(']')) {
             error(current_loc(), "expected ']'");
             return nullptr;
         }
         return std::make_unique<Expr>(loc, Expr::Ty::Mem, std::move(expr));
-    } else if (test(TT::Ident) and m_tok.text == "byte") {
-        step();
+    } else if (eat(TT::KwByte)) {
         if (not eat('[')) {
             error(current_loc(), "expected '['");
             return nullptr;
         }
         auto expr = parse_expr();
+        if (not expr)
+            return nullptr;
         if (not eat(']')) {
             error(current_loc(), "expected ']'");
             return nullptr;
         }
         return std::make_unique<Expr>(loc, Expr::Ty::MemByte, std::move(expr));
-    } else if (test(TT::Ident) and m_tok.text == "word") {
-        step();
+    } else if (eat(TT::KwWord)) {
         if (not eat('[')) {
             error(current_loc(), "expected '['");
             return nullptr;
         }
         auto expr = parse_expr();
+        if (not expr)
+            return nullptr;
         if (not eat(']')) {
             error(current_loc(), "expected ']'");
             return nullptr;
@@ -941,5 +1180,5 @@ auto Parser::current_loc() const -> Loc
 void Parser::error(Loc loc, std::string_view message)
 {
     m_error_occured = true;
-    loc.print_error(m_text, message);
+    loc.print_error(m_text, message, m_filename);
 }
diff --git a/src/assembler.hpp b/src/assembler.hpp
index 855b327..359ff7a 100644
--- a/src/assembler.hpp
+++ b/src/assembler.hpp
@@ -105,13 +105,18 @@ namespace asmer {
 
     class Parser {
     public:
-        explicit Parser(std::string_view text)
-            : m_text(text)
-            , m_lexer(text, Scanner::Kind::Assembler)
+        explicit Parser(std::string_view filename, std::string_view text)
+            : m_filename(filename)
+            , m_text(text)
+            , m_lexer(m_filename, text, Scanner::Kind::Assembler)
             , m_tok(m_lexer.next())
         {
         }
 
+        void eat_whitespace();
+        void try_recover();
+        auto is_done() const -> bool;
+
         auto next_is_const() const -> bool;
         auto parse_const() -> std::unique_ptr<Const>;
 
@@ -141,6 +146,7 @@ namespace asmer {
 
         void error(Loc loc, std::string_view message);
 
+        std::string_view m_filename;
         std::string_view m_text;
         Scanner m_lexer;
         Tok m_tok;
@@ -193,8 +199,9 @@ namespace asmer {
 
     class Assembler {
     public:
-        explicit Assembler(std::string_view text)
-            : m_text(text)
+        explicit Assembler(std::string_view filename, std::string_view text)
+            : m_filename(filename)
+            , m_text(text)
             , m_program(65536)
             , m_builder(m_program.data())
         {
@@ -226,6 +233,7 @@ namespace asmer {
 
         void error(Loc loc, std::string_view message);
 
+        std::string_view m_filename;
         std::string_view m_text;
         std::vector<uint8_t> m_program;
         Builder m_builder;
diff --git a/src/main.cpp b/src/main.cpp
index 13abd9a..4e3ec46 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -3,6 +3,7 @@
 #include "io_device.hpp"
 #include "vm.hpp"
 #include <SDL2/SDL_main.h>
+#include <cstdint>
 #include <print>
 #include <string>
 
@@ -11,14 +12,31 @@ using namespace std::chrono_literals;
 using namespace vc5;
 using namespace vc5::regs;
 
-int main()
+static void make_program(uint8_t* data);
+
+int main(int argc, char** argv)
 {
     auto device = IoDevice::create().value();
     device->set_title("vc5");
 
-    auto disk = MemoryDisk(128);
+    if (argc < 2) {
+        auto disk = MemoryDisk(128);
 
-    auto l = tools::Builder(disk.data());
+        make_program(disk.data());
+
+        auto vm = VM(*device, disk);
+        vm.run();
+    } else {
+        auto disk = FileDisk(argv[1]);
+
+        auto vm = VM(*device, disk);
+        vm.run();
+    }
+}
+
+void make_program(uint8_t* data)
+{
+    auto l = tools::Builder(data);
 
     l.mov_imm(rsp, 0x1000);
     l.mov_reg(rbp, rsp);
@@ -77,9 +95,6 @@ int main()
     l.push(key_press_incr);
     l.set_ip(to_set_key_press_int_leave + 2);
     l.push(key_press_int_leave);
-
-    auto vm = VM(*device, disk);
-    vm.run();
 }
 
 extern "C" const char* __asan_default_options(void)
diff --git a/src/scanner.cpp b/src/scanner.cpp
index 4284f37..660512a 100644
--- a/src/scanner.cpp
+++ b/src/scanner.cpp
@@ -4,6 +4,7 @@
 #include <string>
 #include <string_view>
 #include <unordered_map>
+#include <utility>
 
 using namespace vc5::tools;
 using namespace std::literals;
@@ -130,7 +131,7 @@ auto Scanner::next() -> Tok
         }
         return tok(TT::Gt, loc);
     }
-    if (test_in("\n()[],:|^+-!")) {
+    if (test_in("\n()[].,:|^+-!")) {
         auto ty = static_cast<TT>(current());
         step();
         return tok(ty, loc);
@@ -140,9 +141,21 @@ auto Scanner::next() -> Tok
     return next();
 }
 
-const auto Scanner::keywords_kind_assembler = KeywordMap {
+const Scanner::KeywordMap Scanner::keywords_kind_assembler = {
     { "const", TT::KwConst },
     { "align", TT::KwAlign },
+    { "word", TT::KwWord },
+    { "byte", TT::KwByte },
+    { "r0", TT::KwR0 },
+    { "r1", TT::KwR1 },
+    { "r2", TT::KwR2 },
+    { "r3", TT::KwR3 },
+    { "r4", TT::KwR4 },
+    { "r5", TT::KwR5 },
+    { "rbp", TT::KwRbp },
+    { "rsp", TT::KwRsp },
+    { "rfl", TT::KwRfl },
+    { "rip", TT::KwRip },
 };
 
 void Scanner::step()
@@ -209,19 +222,22 @@ auto Scanner::is_assembler() const -> bool
 void Scanner::error(Loc loc, std::string_view message)
 {
     m_error_occured = true;
-    loc.print_error(m_text, message);
+    loc.print_error(m_text, message, m_filename);
 }
 
-void Loc::print_error(std::string_view text, std::string_view message) const
+void Loc::print_error(std::string_view text,
+    std::string_view message,
+    std::string_view file) const
 {
     constexpr auto type = "error"sv;
 
     constexpr auto clear = "\x1b[0m"sv;
-    constexpr auto bold_red = "\x1b[1;31m"sv;
-    constexpr auto bold_white = "\x1b[1;37m"sv;
+    constexpr auto bold_red = "\x1b[1;91m"sv;
+    constexpr auto bold_white = "\x1b[1;97m"sv;
     constexpr auto cyan = "\x1b[0;36m"sv;
-    constexpr auto gray = "\x1b[0;37m"sv;
-    constexpr auto light_gray = "\x1b[1;30m"sv;
+    constexpr auto gray = "\x1b[0;90m"sv;
+    constexpr auto light_gray = "\x1b[0;37m"sv;
+    constexpr auto green = "\x1b[0;32m"sv;
 
     auto start = text.find_last_of('\n', idx) + 1;
     auto end = text.find_first_of('\n', idx);
@@ -240,13 +256,13 @@ void Loc::print_error(std::string_view text, std::string_view message) const
                  " {8: <{9}}{10}|\n"
                  " {11}{12}{13}|{14}{15}\n"
                  " {16: <{17}}"
-                 "{18}|${19: <{20}}{21}^ {22}{23}{24}",
+                 "{18}|{19: <{20}}{21}^ {22}{23}{24}\n",
         bold_red,
         type,
         bold_white,
         message,
         cyan,
-        "<file>",
+        file,
         line,
         col,
         "",
@@ -255,7 +271,7 @@ void Loc::print_error(std::string_view text, std::string_view message) const
         light_gray,
         linenr_str,
         gray,
-        light_gray,
+        green,
         line_text,
         "",
         linenr_str.size(),
diff --git a/src/scanner.hpp b/src/scanner.hpp
index 36d9255..01b7ea9 100644
--- a/src/scanner.hpp
+++ b/src/scanner.hpp
@@ -11,7 +11,9 @@ struct Loc {
     int line;
     int col;
 
-    void print_error(std::string_view text, std::string_view message) const;
+    void print_error(std::string_view text,
+        std::string_view message,
+        std::string_view file = std::string_view("<file>")) const;
 };
 
 struct Tok {
@@ -25,12 +27,27 @@ struct Tok {
         Str,
         KwConst,
         KwAlign,
+        KwWord,
         Newline = '\n',
+        KwByte,
+        KwR0,
+        KwR1,
+        KwR2,
+        KwR3,
+        KwR4,
+        KwR5,
+        KwRbp,
+        KwRsp,
+        KwRfl,
+        KwRip,
+        LtLt,
+        GtGt,
         LParen = '(',
         RParen = ')',
         LBracket = '[',
         RBracket = ']',
         Comma = ',',
+        Dot = '.',
         Colon = ':',
         Pipe = '|',
         Hat = '^',
@@ -40,8 +57,6 @@ struct Tok {
         Exclam = '!',
         Lt = '<',
         Gt = '>',
-        LtLt,
-        GtGt,
     };
 
     std::string_view text;
@@ -53,8 +68,10 @@ class Scanner {
 public:
     enum class Kind { Assembler };
 
-    explicit Scanner(std::string_view text, Kind kind)
-        : m_text(text)
+    explicit Scanner(
+        std::string_view filename, std::string_view text, Kind kind)
+        : m_filename(filename)
+        , m_text(text)
         , m_keywords(&keywords_kind_assembler)
         , m_kind(kind)
     {
@@ -85,6 +102,7 @@ private:
     using KeywordMap = std::unordered_map<std::string_view, Tok::Ty>;
     static const KeywordMap keywords_kind_assembler;
 
+    std::string_view m_filename;
     std::string_view m_text;
     const KeywordMap* m_keywords;
     size_t m_idx = 0;
diff --git a/vim/ftdetect/vc5asm.vim b/vim/ftdetect/vc5asm.vim
new file mode 100644
index 0000000..0995d06
--- /dev/null
+++ b/vim/ftdetect/vc5asm.vim
@@ -0,0 +1,2 @@
+autocmd BufNewFile,BufRead *.vc5asm setfiletype vc5asm
+
diff --git a/vim/ftplugin/vc5asm.vim b/vim/ftplugin/vc5asm.vim
new file mode 100644
index 0000000..a5299dd
--- /dev/null
+++ b/vim/ftplugin/vc5asm.vim
@@ -0,0 +1,2 @@
+setlocal commentstring=;%s
+
diff --git a/vim/syntax/vc5asm.vim b/vim/syntax/vc5asm.vim
new file mode 100644
index 0000000..9cbde2b
--- /dev/null
+++ b/vim/syntax/vc5asm.vim
@@ -0,0 +1,37 @@
+" Vim syntax file
+" Language: vc5asm
+" Maintainer: SFJ
+" Latest Revision: 1 January 1984
+
+if exists("b:current_syntax")
+  finish
+endif
+
+syn keyword Keyword const align db dw
+syn keyword Keyword nop hlt jmp jnz mov cmp or and xor shl rshl shr rshr add sub rsub
+syn keyword Keyword reti lkbd lvcd dskr dskw
+syn keyword Operator r0 r1 r2 r3 r4 r5 rbp rsp rfl rip
+
+syn match Operator '+'
+syn match Operator '-'
+syn match Operator '='
+syn match Operator '<'
+syn match Operator '>'
+syn match Operator '|'
+syn match Operator '^'
+syn match Operator '&'
+
+
+syn match Number '0'
+syn match Number '[1-9][0-9]*'
+syn match Number '0b[01]*'
+syn match Number '0x[0-9a-fA-F]*'
+
+syn region String start=+"+  skip=+\\\\\|\\"+  end=+"+
+
+syn match Comment ";.*$"
+
+syn match Identifier '[a-zA-Z_]\w*'
+
+let b:current_syntax = "vc5asm"
+