diff --git a/programs/boot.vc5asm b/programs/boot.vc5asm
index ed74de5..338e7b8 100644
--- a/programs/boot.vc5asm
+++ b/programs/boot.vc5asm
@@ -1,13 +1,20 @@
 
 
-const KBD_STATUS 0x1ffc
-const KBD_CODE 0x1ffe
-const VCD 0x2000
+const fl_zero 0x1
+const fl_eq 0x2
+const fl_be 0x4
+const fl_lt 0x8
+const fl_err 0xa
 
-const FL_EQ 0x2
+const vcd_base 0x2000
 
-const KBD_FLAG_IS_RELEASE 0x1
+const kbd_status 0x1ffc
+const kbd_code 0x1ffe
+const kbd_flag_is_release 0x1
 
+const counter 0x600
+
+_start:
     mov rsp, 0x1000
     mov rbp, rsp
 
@@ -18,7 +25,7 @@ const KBD_FLAG_IS_RELEASE 0x1
     ; setup video character display (VCD)
     ; descriptor table structure:
     ;   [addr + 0] memory map base
-    mov r0, VCD
+    mov r0, vcd_base
     mov [0x700], r0
     lvcd 0x700
 
@@ -27,9 +34,9 @@ const KBD_FLAG_IS_RELEASE 0x1
     ;   [addr + 0] status address
     ;   [addr + 2] keycode address
     ;   [addr + 4] keyboard interrupt handler
-    mov r0, KBD_STATUS
+    mov r0, kbd_status
     mov [0x702], r0
-    mov r0, KBD_CODE
+    mov r0, kbd_code
     mov [0x704], r0
     mov r0, key_press_int
     mov [0x706], r0
@@ -37,33 +44,91 @@ const KBD_FLAG_IS_RELEASE 0x1
 
     ; character counter
     mov r0, 0
-    mov [0x600], r0
+    mov [counter], r0
 
 main_loop:
     hlt
     jmp main_loop
     
 key_press_int:
-    mov r0, [KBD_STATUS]
-    and r0, r0, KBD_FLAG_IS_RELEASE
+    mov r0, [kbd_status]
+    and r0, kbd_flag_is_release
     jnz r0, .leave
 
-    mov r0, [0x600]
-    add r0, r0, VCD
-    mov r1, [KBD_CODE]
+    mov r0, [counter]
+    add r0, vcd_base
+    mov r1, [kbd_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
+    and r2, fl_eq
+;    jnz r2, .incr
+;    add r1, 61
+;    mov byte [r0], r1
+;.incr:
+;    mov r0, [counter]
+;    add r0, 1
+;    mov [counter], r0
+
+    jnz r2, .print_space
+    add r1, 61 ; scancode letter -> ascii
+    mov [rsp], r0
+    add rsp, 2
+    call print_char
+    jmp .leave
+.print_space:
+    mov r0, ' '
+    mov [rsp], r0
+    add rsp, 2
+    call print_char
 .leave:
     reti
 
+print_char:
+    mov [rsp], rbp
+    mov rbp, rsp
+    add rsp, 2
+
+    mov r1, [rbp-6]
+
+    add r0, vcd_base
+    mov r1, [kbd_code]
+    cmp r1, ' '
+    mov r2, rfl
+    and r2, fl_eq
+    jnz r2, .incr
+    add r1, 61
+    mov byte [r0], r1
+.incr:
+    mov r0, [counter]
+    add r0, 1
+    mov [counter], r0
+.leave:
+    sub rsp, 2
+    mov rbp, [rsp]
+    ret
+
+;print_int:
+;    mov [rsp], rbp
+;    add rsp, 2
+;    mov rbp, rsp
+;    add rsp, rsp, 2
+;
+;    mov r1, [rbp-2]
+;
+;    mov r2, 10000
+;    mov r3, 0
+;    jmp .c_10000
+;.b_10000:
+;    add r3, 1
+;    sub r1, r2
+;.c_10000:
+;    cmp r2, r1
+;    mov r0, rfl
+;    and r0, fl_eq | fl_lt
+;    jnz r0, .b_10000
+;    add r3, 48
+
+
 ;scancode_to_char:
 ;    cmp r1, 61
 ;
diff --git a/src/assembler.cpp b/src/assembler.cpp
index 36c2341..7a61e5a 100644
--- a/src/assembler.cpp
+++ b/src/assembler.cpp
@@ -101,7 +101,11 @@ auto Assembler::assemble_file()
             }
 
             assert(value->ty == EOT::Imm);
-            m_syms[std::string(stmt->ident)] = value->as_imm();
+            if (auto result
+                = define_sym(std::string(stmt->ident), value->as_imm());
+                not result) {
+                error(stmt->loc, result.error());
+            }
 
         } else if (parser.next_is_align()) {
             auto stmt = parser.parse_align();
@@ -172,9 +176,20 @@ auto Assembler::assemble_file()
     m_second_pass = true;
 
     for (const auto& line : lines) {
+        if (line->labels) {
+            for (const auto& label : *line->labels) {
+                if (not label.is_local) {
+                    m_superlabel = label.ident;
+                }
+            }
+        }
+
         assemble_line(*line);
     }
 
+    if (m_failed)
+        return std::unexpected("assembling failed");
+
     return std::move(m_program);
 }
 
@@ -182,10 +197,17 @@ void Assembler::define_labels(const std::vector<Label>& labels)
 {
     for (const auto& label : labels) {
         if (label.is_local) {
-            m_syms[label_ident(label)] = m_builder.ip();
+            if (auto result = define_sym(label_ident(label), m_builder.ip());
+                not result) {
+                error(label.loc, result.error());
+            }
         } else {
             m_superlabel = label.ident;
-            m_syms[std::string(label.ident)] = m_builder.ip();
+            if (auto result
+                = define_sym(std::string(label.ident), m_builder.ip());
+                not result) {
+                error(label.loc, result.error());
+            }
         }
     }
 }
@@ -205,36 +227,62 @@ auto Assembler::sublabel_ident(std::string_view ident) const -> std::string
 namespace {
 
 enum class Mnemonic {
-    // clang-format off
-    db,    dw,    nop,
-    hlt,   jmp,   jnz,
-    mov,   cmp,
-    or_,   and_,  xor_,
-    shl,   rshl,  shr,
-    rshr,  add,   sub,
-    rsub,  reti,  lvcd,
-    lkbd,  dskr,  dskw,
-    // clang-format on
+    db,
+    dw,
+    nop,
+    hlt,
+    jmp,
+    jnz,
+    mov,
+    cmp,
+    or_,
+    and_,
+    xor_,
+    shl,
+    rshl,
+    shr,
+    rshr,
+    add,
+    sub,
+    rsub,
+    call,
+    ret,
+    reti,
+    lvcd,
+    lkbd,
+    dskr,
+    dskw,
 };
 
 using M = Mnemonic;
 
 static const auto mnemonic_map
     = std::unordered_map<std::string_view, Mnemonic> {
-          // clang-format off
-          { "db", M::db },        { "dw", M::dw },
-          { "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 },
-          { "rshl", M::rshl },    { "shr", M::shr },
-          { "rshr", M::rshr },    { "add", M::add },
-          { "sub", M::sub },      { "rsub", M::rsub },
-          { "reti", M::reti },    { "lvcd", M::lvcd },
-          { "lkbd", M::lkbd },    { "dskr", M::dskr },
+          { "db", M::db },
+          { "dw", M::dw },
+          { "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 },
+          { "rshl", M::rshl },
+          { "shr", M::shr },
+          { "rshr", M::rshr },
+          { "add", M::add },
+          { "sub", M::sub },
+          { "rsub", M::rsub },
+          { "call", M::call },
+          { "ret", M::ret },
+          { "reti", M::reti },
+          { "lvcd", M::lvcd },
+          { "lkbd", M::lkbd },
+          { "dskr", M::dskr },
           { "dskw", M::dskw },
-          // clang-format on
       };
 
 }
@@ -412,11 +460,24 @@ void Assembler::assemble_line(const Line& line)
         case M::add:
         case M::sub:
         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]);
+            auto dst = std::unique_ptr<EvaledOperand> {};
+            auto op1_store = std::unique_ptr<EvaledOperand> {};
+            auto op2 = std::unique_ptr<EvaledOperand> {};
+
+            EvaledOperand* op1;
+
+            if (line.args.size() == 3) {
+                dst = eval_operand(*line.args[0]);
+                op1_store = eval_operand(*line.args[1]);
+                op1 = &*op1_store;
+                op2 = eval_operand(*line.args[2]);
+            } else if (line.args.size() == 2) {
+                dst = eval_operand(*line.args[0]);
+                op1 = &*dst;
+                op2 = eval_operand(*line.args[1]);
+            } else {
+                operation_not_supported();
+            }
 
             if (not dst or not op1 or not op2)
                 return;
@@ -501,6 +562,28 @@ void Assembler::assemble_line(const Line& line)
             }
             break;
         }
+        case Mnemonic::call: {
+            if (arg_count_wrong(line, 1))
+                return;
+            auto op = eval_operand(*line.args[0]);
+            if (not op)
+                return;
+
+            if (op->is_reg()) {
+                l.call_reg(op->as_reg());
+            } else if (op->is_imm()) {
+                l.call_imm(op->as_imm());
+            } else {
+                operation_not_supported();
+            }
+            break;
+        }
+        case Mnemonic::ret: {
+            if (arg_count_wrong(line, 0))
+                return;
+            l.ret();
+            break;
+        }
         case M::reti: {
             if (arg_count_wrong(line, 0))
                 return;
@@ -715,32 +798,28 @@ auto Assembler::eval_operand_to_imm(const Expr& expr)
     auto loc = expr.loc;
     switch (expr.ty) {
         case Expr::Ty::Ident: {
-            auto ident = std::string(expr.as_ident());
-            if (!m_syms.contains(ident)) {
+            auto result = get_sym(std::string(expr.as_ident()));
+            if (not result) {
                 if (not m_second_pass)
                     return std::make_unique<EO>(loc, EOT::Imm, uint16_t { 0 });
 
-                error(expr.loc,
-                    std::format("symbol \"{}\" not defined", expr.as_ident()));
+                error(expr.loc, result.error());
                 return nullptr;
             }
 
-            auto value = m_syms[ident];
-            return std::make_unique<EO>(loc, EOT::Imm, value);
+            return std::make_unique<EO>(loc, EOT::Imm, *result);
         }
         case Expr::Ty::SubLabel: {
-            auto ident = sublabel_ident(expr.as_ident());
-            if (!m_syms.contains(ident)) {
+            auto result = get_sym(sublabel_ident(expr.as_ident()));
+            if (not result) {
                 if (not m_second_pass)
                     return std::make_unique<EO>(loc, EOT::Imm, uint16_t { 0 });
 
-                error(expr.loc,
-                    std::format("symbol \"{}\" not defined", expr.as_ident()));
+                error(expr.loc, result.error());
                 return nullptr;
             }
 
-            auto value = m_syms[ident];
-            return std::make_unique<EO>(loc, EOT::Imm, value);
+            return std::make_unique<EO>(loc, EOT::Imm, *result);
         }
         case Expr::Ty::Reg:
             error(loc, "registers cannot be part of an expression");
@@ -830,6 +909,32 @@ bool Assembler::arg_count_wrong(const Line& ins, size_t count)
     return false;
 }
 
+auto Assembler::define_sym(std::string ident, uint16_t value)
+    -> std::expected<void, std::string>
+{
+    std::println("define_sym(\"{}\", {})", ident, value);
+
+    if (m_syms.contains(ident)) {
+        return std::unexpected(
+            std::format("symbol \"{}\" already defined", ident));
+    }
+
+    m_syms[std::move(ident)] = value;
+    return {};
+}
+
+auto Assembler::get_sym(const std::string& ident)
+    -> std::expected<uint16_t, std::string>
+{
+    std::println("  get_sym(\"{}\")", ident);
+
+    if (not m_syms.contains(ident)) {
+        return std::unexpected(std::format("symbol \"{}\" not defined", ident));
+    }
+
+    return m_syms[ident];
+}
+
 void Assembler::error(Loc loc, std::string_view message)
 {
     m_failed = true;
@@ -1003,15 +1108,19 @@ auto Parser::parse_binary(int prec) -> std::unique_ptr<Expr>
 
     auto left = parse_binary(prec - 1);
 
-    auto should_continue = false;
+    auto should_continue = true;
     while (should_continue) {
         should_continue = false;
         for (auto [op, ty, p] : ops) {
             if (prec >= p and eat(op)) {
                 auto right = parse_binary(prec - 1);
+
                 left = std::make_unique<Expr>(loc,
                     ty,
                     Expr::Binary { std::move(left), std::move(right) });
+
+                should_continue = true;
+                break;
             }
         }
     }
@@ -1022,13 +1131,14 @@ auto Parser::parse_binary(int prec) -> std::unique_ptr<Expr>
 auto Parser::parse_prefix() -> std::unique_ptr<Expr>
 {
     auto loc = current_loc();
-    auto expr = parse_operand();
+
+    auto next = [&]() { return parse_operand(); };
     if (eat('-')) {
-        return std::make_unique<Expr>(loc, Expr::Ty::Negate, std::move(expr));
+        return std::make_unique<Expr>(loc, Expr::Ty::Negate, next());
     } else if (eat('!')) {
-        return std::make_unique<Expr>(loc, Expr::Ty::Not, std::move(expr));
+        return std::make_unique<Expr>(loc, Expr::Ty::Not, next());
     } else {
-        return expr;
+        return next();
     }
 }
 
diff --git a/src/assembler.hpp b/src/assembler.hpp
index 31d95f1..c4176b6 100644
--- a/src/assembler.hpp
+++ b/src/assembler.hpp
@@ -234,6 +234,11 @@ namespace asmer {
         /// true means fail
         bool arg_count_wrong(const Line& ins, size_t count);
 
+        auto define_sym(std::string ident, uint16_t value)
+            -> std::expected<void, std::string>;
+        auto get_sym(const std::string& ident)
+            -> std::expected<uint16_t, std::string>;
+
         void error(Loc loc, std::string_view message);
 
         std::string_view m_filename;
diff --git a/src/builder.cpp b/src/builder.cpp
index bf7ba69..872591d 100644
--- a/src/builder.cpp
+++ b/src/builder.cpp
@@ -373,6 +373,29 @@ void Builder::binary_imm(Reg dst, Reg op1, uint16_t op2, Op op)
     i.build(*this);
 }
 
+void Builder::call_reg(Reg op1)
+{
+    LOG;
+    auto i = InsBuilder(Op::Call);
+    i.op1_reg(op1);
+    i.build(*this);
+}
+
+void Builder::call_imm(uint16_t op1)
+{
+    LOG;
+    auto i = InsBuilder(Op::Call);
+    i.imm(op1);
+    i.build(*this);
+}
+
+void Builder::ret()
+{
+    LOG;
+    auto i = InsBuilder(Op::Ret);
+    i.build(*this);
+}
+
 void Builder::reti()
 {
     LOG;
diff --git a/src/builder.hpp b/src/builder.hpp
index 4af5f28..92c7c5c 100644
--- a/src/builder.hpp
+++ b/src/builder.hpp
@@ -53,6 +53,9 @@ public:
     void add_imm(Reg dst, Reg op1, uint16_t op2);
     void sub_imm(Reg dst, Reg op1, uint16_t op2);
     void rsub_imm(Reg dst, Reg op1, uint16_t op2);
+    void call_reg(Reg op1);
+    void call_imm(uint16_t op1);
+    void ret();
     void reti();
     void lvcd_reg(Reg op1);
     void lvcd_imm(uint16_t op1);
diff --git a/src/io_device.cpp b/src/io_device.cpp
index c9b83f8..63dbbe3 100644
--- a/src/io_device.cpp
+++ b/src/io_device.cpp
@@ -70,6 +70,8 @@ auto IoDevice::create() -> std::expected<std::unique_ptr<IoDevice>, std::string>
         if (SDL_Init(SDL_INIT_VIDEO) != 0) {
             return std::unexpected(SDL_GetError());
         }
+
+        SDL_StopTextInput();
     }
 
     SDL_Window* window;
@@ -204,8 +206,8 @@ auto IoDevice::poll_event() -> std::unique_ptr<IoEvent>
                         = (event.key.keysym.mod & KMOD_RALT) != 0,
                     });
                 // default:
-                // std::println(stderr, "warning: unhandled event '{}'",
-                // event.type);
+                //     std::println(
+                //         stderr, "warning: unhandled event '{}'", event.type);
         }
     }
 
diff --git a/src/vm.cpp b/src/vm.cpp
index edc3404..e6fd4cb 100644
--- a/src/vm.cpp
+++ b/src/vm.cpp
@@ -6,7 +6,9 @@
 #include <print>
 #include <stdexcept>
 #include <string_view>
+#include <thread>
 #include <utility>
+#include <vector>
 
 using namespace vc5;
 using namespace std::literals;
@@ -16,6 +18,93 @@ void VM::load(uint16_t offset, const uint8_t* data, size_t data_size)
     std::memcpy(&m_mem[offset], data, data_size);
 }
 
+namespace {
+
+class Debugger {
+public:
+    explicit Debugger(VM& vm)
+        : vm(&vm)
+    {
+    }
+
+    void run_on_line(bool halted)
+    {
+        if (halted) {
+            m_halted_last_call = true;
+            return;
+        }
+
+        if (m_continue) {
+            if (m_halted_last_call and m_break_on_halt) {
+                m_continue = false;
+            } else {
+                auto ip = vm->reg(Reg::Rip);
+                for (const auto& addr : m_break_on_address) {
+                    if (addr == ip) {
+                        m_continue = false;
+                        break;
+                    }
+                }
+            }
+
+            if (m_continue)
+                return;
+        }
+
+        m_halted_last_call = false;
+
+        auto line = std::string();
+        do {
+            std::print("> ");
+            std::cout.flush();
+            std::getline(std::cin, line);
+
+            if (line == "r") {
+                for (uint16_t reg = 0; reg < 10; ++reg) {
+                    constexpr auto reg_strs = std::array {
+                        "r0"sv,
+                        "r1"sv,
+                        "r2"sv,
+                        "r3"sv,
+                        "r4"sv,
+                        "r5"sv,
+                        "rbp"sv,
+                        "rsp"sv,
+                        "rfl"sv,
+                        "rip"sv,
+                    };
+                    std::println("    {: <3} | {:04x} {: 5}",
+                        reg_strs[reg],
+                        vm->reg(static_cast<Reg>(reg)),
+                        vm->reg(static_cast<Reg>(reg)));
+                }
+            } else if (line == "c") {
+                m_continue = true;
+                break;
+            } else if (line == "brhlt") {
+                m_break_on_halt = true;
+            } else if (line.starts_with("p")) {
+                uint16_t v
+                    = std::strtoul(line.c_str() + 2, nullptr, 16) & 0xfffe;
+                std::println("[{: 4x}] {: 4x}", v, vm->word(v));
+            } else if (line.starts_with("br")) {
+                uint16_t v
+                    = std::strtoul(line.c_str() + 3, nullptr, 16) & 0xfffe;
+                m_break_on_address.push_back(v);
+            }
+        } while (!line.empty());
+    }
+
+private:
+    VM* vm;
+    std::vector<uint16_t> m_break_on_address {};
+    bool m_halted_last_call = false;
+    bool m_break_on_halt = false;
+    bool m_continue = false;
+};
+
+}
+
 int VM::run()
 {
     constexpr uint16_t bootloader_size = 512;
@@ -23,6 +112,8 @@ int VM::run()
         m_disk->read(&m_mem[i * m_disk->block_size], i);
     }
 
+    auto debugger = Debugger(*this);
+
     m_on = true;
     while (m_on) {
         if (not m_halted) {
@@ -31,42 +122,12 @@ int VM::run()
                 return result;
         }
 
-        // if (not m_halted) {
-        //     auto line = std::string();
-        //     do {
-        //         std::print("> ");
-        //         std::cout.flush();
-        //         std::getline(std::cin, line);
-        //
-        //         if (line == "r") {
-        //             for (uint16_t reg = 0; reg < 10; ++reg) {
-        //                 constexpr auto reg_strs = std::array {
-        //                     "R0"sv,
-        //                     "R1"sv,
-        //                     "R2"sv,
-        //                     "R3"sv,
-        //                     "R4"sv,
-        //                     "R5"sv,
-        //                     "Rbp"sv,
-        //                     "Rsp"sv,
-        //                     "Rfl"sv,
-        //                     "Rip"sv,
-        //                 };
-        //                 std::println("    {: <3} | {:04x} {: 5}",
-        //                     reg_strs[reg],
-        //                     m_regs[reg],
-        //                     m_regs[reg]);
-        //             }
-        //         } else if (line.starts_with("p")) {
-        //             uint16_t v
-        //                 = std::strtoul(line.c_str() + 2, nullptr, 16) &
-        //                 0xfffe;
-        //             std::println("[{: 4x}] {: 4x}", v, word(v));
-        //         }
-        //     } while (!line.empty());
-        // }
+        // debugger.run_on_line(m_halted);
 
         poll_events();
+        if (m_halted) {
+            std::this_thread::sleep_for(15ms);
+        }
     }
     return 0;
 }
@@ -255,7 +316,7 @@ int VM::run_instruction()
             break;
         }
         case Op::LoadWord: {
-            auto addr = ins.mem_addr(ins.op2(), eat_word());
+            auto addr = ins.mem_addr(ins.op1(), eat_word());
 
             if ((addr & 0b1) != 0) {
                 std::println(stderr,
@@ -293,7 +354,7 @@ int VM::run_instruction()
             break;
         }
         case Op::LoadByte: {
-            auto addr = ins.mem_addr(ins.op2(), eat_word());
+            auto addr = ins.mem_addr(ins.op1(), eat_word());
             auto reg = ins.dst_reg();
 
             set_reg(reg, byte(addr));
@@ -384,6 +445,22 @@ int VM::run_instruction()
 
             break;
         }
+        case Op::Call: {
+            auto op1 = ins.op1_or_imm();
+
+            auto return_addr = word(*m_rip);
+            set_word(*m_rsp, return_addr);
+            *m_rsp -= 2;
+
+            *m_rip = op1;
+            break;
+        }
+        case Op::Ret: {
+            *m_rsp -= 2;
+            auto return_addr = word(*m_rsp);
+            *m_rip = return_addr;
+            break;
+        }
         case Op::RetI: {
             *m_rsp -= 2;
             auto return_addr = word(*m_rsp);
@@ -469,6 +546,7 @@ void VM::poll_events()
                 set_word(d.keycode_addr, event->as_key_event().key);
                 interrupt(d.int_handler);
             }
+            continue;
         }
     }
 }
@@ -544,6 +622,10 @@ const char* vc5::op_str(Op op)
             return "Sub";
         case Op::RSub:
             return "RSub";
+        case Op::Call:
+            return "Call";
+        case Op::Ret:
+            return "Ret";
         case Op::RetI:
             return "RetI";
         case Op::LVCD:
diff --git a/src/vm.hpp b/src/vm.hpp
index c1f5900..ebc68fb 100644
--- a/src/vm.hpp
+++ b/src/vm.hpp
@@ -33,6 +33,9 @@ enum class Op : uint16_t {
     Sub,
     RSub,
 
+    Call,
+    Ret,
+
     // return from interrupt
     RetI,
     // load video character display
diff --git a/vim/syntax/vc5asm.vim b/vim/syntax/vc5asm.vim
index 9cbde2b..386914e 100644
--- a/vim/syntax/vc5asm.vim
+++ b/vim/syntax/vc5asm.vim
@@ -9,7 +9,7 @@ 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 Keyword call ret reti lkbd lvcd dskr dskw
 syn keyword Operator r0 r1 r2 r3 r4 r5 rbp rsp rfl rip
 
 syn match Operator '+'
@@ -27,6 +27,8 @@ syn match Number '[1-9][0-9]*'
 syn match Number '0b[01]*'
 syn match Number '0x[0-9a-fA-F]*'
 
+syn match Character "'\\\?.'"
+
 syn region String start=+"+  skip=+\\\\\|\\"+  end=+"+
 
 syn match Comment ";.*$"