diff --git a/src/collections/List.h b/src/collections/List.h
index b5adcad..633f04b 100644
--- a/src/collections/List.h
+++ b/src/collections/List.h
@@ -13,7 +13,7 @@
     }\
     \
     static inline List_##T List_##T##_alloc(u32 len){\
-        return List_##T##_construct(len > 0 ? malloc(len * sizeof(T)) : NULL, 0, 0);\
+        return List_##T##_construct((T*)(len > 0 ? malloc(len * sizeof(T)) : NULL), 0, 0);\
     }\
     \
     void List_##T##_push(List_##T* ptr, T value);
@@ -27,7 +27,7 @@
             max_len += __List_padding_in_sizeof_T(T);\
             /* branchless version of max(max_len, __List_min_size) */\
             max_len += (max_len < __List_min_size) * (__List_min_size - max_len);\
-            ptr->data = realloc(ptr->data, max_len * sizeof(T));\
+            ptr->data = (T*)realloc(ptr->data, max_len * sizeof(T));\
             ptr->max_len = max_len;\
         }\
         ptr->data[ptr->len++] = value;\
diff --git a/src/compiler/AST.h b/src/compiler/AST.h
new file mode 100644
index 0000000..ad37846
--- /dev/null
+++ b/src/compiler/AST.h
@@ -0,0 +1,39 @@
+#pragma once
+#include "../std.h"
+#include "../instructions/instructions.h"
+#include "../collections/List.h"
+
+typedef enum ArgumentType {
+    ArgumentType_NoArgument,
+    ArgumentType_Register,
+    ArgumentType_ConstValue,
+    ArgumentType_Name,
+    ArgumentType_NamedDataPointer,
+    ArgumentType_NamedDataSize,
+};
+
+typedef struct Argument {
+    ArgumentType type;
+    u32 value;
+} Argument;
+
+typedef struct DataDefinition {
+    u8 element_size;
+    u16 size;
+    void* data;
+    cstr name;
+};
+
+List_declare(DataDefinition);
+
+typedef struct AST {
+    DataDefinition
+} AST;
+
+/*
+d8 name ''
+
+goto label
+.label:
+code...
+*/
\ No newline at end of file
diff --git a/src/compiler/compiler.c b/src/compiler/compiler.c
index c4130f9..79bb79a 100644
--- a/src/compiler/compiler.c
+++ b/src/compiler/compiler.c
@@ -1,8 +1,8 @@
-#include "compiler.h"
+#include "Lexer.h"
 
 List_define(Token);
 
-CodePos Compiler_getLineAndColumn(Compiler* cmp, u32 pos){
+CodePos Lexer_getLineAndColumn(Lexer* cmp, u32 pos){
     u32 prev_lines_len = 0;
     if(pos >= cmp->code_len)
         return CodePos_create(0, 0);
@@ -17,18 +17,18 @@ CodePos Compiler_getLineAndColumn(Compiler* cmp, u32 pos){
     return CodePos_create(0, 0);
 }
 
-static void completeLine(Compiler* cmp){
+static void completeLine(Lexer* cmp){
     List_u32_push(&cmp->line_lengths, cmp->column);
     cmp->column = 0;
 }
 
-void _Compiler_setError(Compiler* cmp, cstr context, cstr format, ...){
+void _Lexer_setError(Lexer* cmp, cstr context, cstr format, ...){
     completeLine(cmp);
     // happens at the end of file
     if(cmp->pos >= cmp->code_len)
         cmp->pos = cmp->code_len - 1;
     char position_str[32];
-    CodePos code_pos = Compiler_getLineAndColumn(cmp, cmp->pos);
+    CodePos code_pos = Lexer_getLineAndColumn(cmp, cmp->pos);
     sprintf(position_str, "[at %u:%u][", code_pos.line, code_pos.column);
     char* real_format = strcat_malloc(position_str, context, "] ", format);
     va_list argv;
@@ -40,12 +40,12 @@ void _Compiler_setError(Compiler* cmp, cstr context, cstr format, ...){
         buf = malloc(16);
         strcpy(buf, "SPRINTF FAILED");
     }
-    cmp->state = CompilerState_Error;
+    cmp->state = LexerState_Error;
     cmp->error_message = buf;
 }
 
 
-#define setError(FORMAT, ...) Compiler_setError(cmp, FORMAT, ##__VA_ARGS__)
+#define setError(FORMAT, ...) Lexer_setError(cmp, FORMAT, ##__VA_ARGS__)
 
 #define returnError(FORMAT, ...) {\
     setError(FORMAT, ##__VA_ARGS__);\
@@ -59,20 +59,20 @@ void _Compiler_setError(Compiler* cmp, cstr context, cstr format, ...){
 #define Error_unexpectedCharacter(C) "unexpected character '%c'", C
 #define Error_endOfFile "unexpected end of file"
 
-void Compiler_init(Compiler* cmp){
-    memset(cmp, 0, sizeof(Compiler));
-    cmp->state = CompilerState_Initial;
+void Lexer_init(Lexer* cmp){
+    memset(cmp, 0, sizeof(Lexer));
+    cmp->state = LexerState_Initial;
     cmp->tokens = List_Token_alloc(4096);
     cmp->line_lengths = List_u32_alloc(1024);
 }
 
-void Compiler_free(Compiler* cmp){
+void Lexer_free(Lexer* cmp){
     free(cmp->code);
     free(cmp->tokens.data);
     free(cmp->line_lengths.data);
 }
 
-static void readCommentSingleLine(Compiler* cmp){
+static void readCommentSingleLine(Lexer* cmp){
     char c; // '/'
     Token tok = Token_construct(TokenType_SingleLineComment, cmp->pos - 1, 0);
     cmp->column++;
@@ -97,7 +97,7 @@ static void readCommentSingleLine(Compiler* cmp){
     List_Token_push(&cmp->tokens, tok);
 }
 
-static void readCommentMultiLine(Compiler* cmp){
+static void readCommentMultiLine(Lexer* cmp){
     char c; // '*'
     Token tok = Token_construct(TokenType_MultiLineComment, cmp->pos - 1, 0);
     cmp->column++;
@@ -122,7 +122,7 @@ static void readCommentMultiLine(Compiler* cmp){
     setError(Error_endOfFile);
 }
 
-static void readComment(Compiler* cmp){
+static void readComment(Lexer* cmp){
     char c; // '/'
     if(cmp->pos + 1 == cmp->code_len){
         setError(Error_endOfFile);
@@ -144,7 +144,7 @@ static void readComment(Compiler* cmp){
     else setError(Error_unexpectedCharacter(c));
 }
 
-static void readLabel(Compiler* cmp){
+static void readLabel(Lexer* cmp){
     char c; // '.'
     cmp->pos++;
     cmp->column++;
@@ -179,7 +179,7 @@ static void readLabel(Compiler* cmp){
     else setError(Error_endOfFile);
 }
 
-static void readArguments(Compiler* cmp){
+static void readArguments(Lexer* cmp){
     char c; // space
     cmp->pos++;
     cmp->column++;
@@ -215,7 +215,7 @@ static void readArguments(Compiler* cmp){
         List_Token_push(&cmp->tokens, tok);
 }
 
-static void readInstruction(Compiler* cmp){
+static void readInstruction(Lexer* cmp){
     Token tok = Token_construct(TokenType_Instruction, cmp->pos, 0);
     cmp->pos++;
     cmp->column++;
@@ -252,7 +252,7 @@ static void readInstruction(Compiler* cmp){
     List_Token_push(&cmp->tokens, tok);
 }
 
-static void readChar(Compiler* cmp){
+static void readChar(Lexer* cmp){
     Token tok = Token_construct(TokenType_Char, cmp->pos, 0);
     cmp->pos++;
     cmp->column++;
@@ -279,7 +279,7 @@ static void readChar(Compiler* cmp){
     setError(Error_endOfFile);
 }
 
-static void readString(Compiler* cmp){
+static void readString(Lexer* cmp){
     Token tok = Token_construct(TokenType_String, cmp->pos, 0);
     cmp->pos++;
     cmp->column++;
@@ -306,7 +306,7 @@ static void readString(Compiler* cmp){
     setError(Error_endOfFile);
 }
 
-static void readNumber(Compiler* cmp){
+static void readNumber(Lexer* cmp){
     Token tok = Token_construct(TokenType_Number, cmp->pos, 0);
     cmp->pos++;
     cmp->column++;
@@ -329,9 +329,9 @@ static void readNumber(Compiler* cmp){
     List_Token_push(&cmp->tokens, tok);
 }
 
-static bool lex(Compiler* cmp){
-    returnErrorIf_auto(cmp->state != CompilerState_Initial);
-    cmp->state = CompilerState_Lexing;
+static bool lex(Lexer* cmp){
+    returnErrorIf_auto(cmp->state != LexerState_Initial);
+    cmp->state = LexerState_Lexing;
     cmp->column = 1;
 
     while(cmp->pos < cmp->code_len){
@@ -364,7 +364,7 @@ static bool lex(Compiler* cmp){
                 break;
         }
 
-        if(cmp->state == CompilerState_Error)
+        if(cmp->state == LexerState_Error)
             return false;
         
         c = cmp->code[cmp->pos];
@@ -378,20 +378,20 @@ static bool lex(Compiler* cmp){
     return true;
 }
 
-static bool parse(Compiler* cmp){
-    returnErrorIf_auto(cmp->state != CompilerState_Lexing);
-    cmp->state = CompilerState_Parsing;
+static bool parse(Lexer* cmp){
+    returnErrorIf_auto(cmp->state != LexerState_Lexing);
+    cmp->state = LexerState_Parsing;
 
     return true;
 }
-static bool compile(Compiler* cmp, FILE* f){
-    returnErrorIf_auto(cmp->state != CompilerState_Parsing);
-    cmp->state = CompilerState_Compiling;
+static bool compile(Lexer* cmp, FILE* f){
+    returnErrorIf_auto(cmp->state != LexerState_Parsing);
+    cmp->state = LexerState_Compiling;
 
     return true;
 }
 
-bool Compiler_compileTasm(Compiler* cmp, cstr source_file_name, cstr out_file_name, bool debug){
+bool Lexer_compileTasm(Lexer* cmp, cstr source_file_name, cstr out_file_name, bool debug){
     FILE* f = fopen(source_file_name, "rb");
     if(f == NULL)
         returnError("ERROR: can't open file '%s'", source_file_name);
@@ -439,7 +439,7 @@ bool Compiler_compileTasm(Compiler* cmp, cstr source_file_name, cstr out_file_na
         printf("------------------------------------[tokens]-----------------------------------\n");
         for(u32 i = 0; i < cmp->tokens.len; i++){
             Token t = cmp->tokens.data[i];
-            CodePos pos = Compiler_getLineAndColumn(cmp, t.begin);
+            CodePos pos = Lexer_getLineAndColumn(cmp, t.begin);
             char* tokstr = malloc(4096);
             strncpy(tokstr, cmp->code + t.begin, t.length);
             tokstr[t.length] = 0;
@@ -463,7 +463,7 @@ bool Compiler_compileTasm(Compiler* cmp, cstr source_file_name, cstr out_file_na
     success = compile(cmp, f);
     fclose(f);
     if(success){
-        cmp->state = CompilerState_Success;
+        cmp->state = LexerState_Success;
     }
     
     return success;
diff --git a/src/compiler/compiler.h b/src/compiler/compiler.h
index 3de4227..5390407 100644
--- a/src/compiler/compiler.h
+++ b/src/compiler/compiler.h
@@ -2,38 +2,39 @@
 #include "../std.h"
 #include "../collections/List.h"
 #include "token.h"
+#include "AST.h"
 
 List_declare(Token);
 
-typedef enum CompilerState {
-    CompilerState_Initial,
-    CompilerState_Lexing,
-    CompilerState_Parsing,
-    CompilerState_Compiling,
-    CompilerState_Error,
-    CompilerState_Success
-} CompilerState;
+typedef enum LexerState {
+    LexerState_Initial,
+    LexerState_Lexing,
+    LexerState_Parsing,
+    LexerState_Compiling,
+    LexerState_Error,
+    LexerState_Success
+} LexerState;
 
-typedef struct Compiler {
+typedef struct Lexer {
     char* code;
     u32 code_len;
     u32 column;     // > 0 if code parsing started
     u32 pos;
-    CompilerState state;
+    LexerState state;
     NULLABLE(char* error_message);
     List_Token tokens;
     List_u32 line_lengths;
-} Compiler;
+} Lexer;
 
-void Compiler_init(Compiler* cmp);
-void Compiler_free(Compiler* cmp);
+void Lexer_init(Lexer* cmp);
+void Lexer_free(Lexer* cmp);
 
 /// @brief compile assembly language code to machine code
 /// @return true if no errors, false if any error occured (check cmp->error_message)
-bool Compiler_compileTasm(Compiler* cmp, cstr source_file_name, cstr out_file_name, bool debug);
+bool Lexer_compileTasm(Lexer* cmp, cstr source_file_name, cstr out_file_name, bool debug);
 
-#define Compiler_setError(cmp, format, ...) _Compiler_setError(cmp, __func__, format ,##__VA_ARGS__)
-void _Compiler_setError(Compiler* cmp, cstr context, cstr format, ...) __attribute__((__format__(__printf__, 3, 4)));
+#define Lexer_setError(cmp, format, ...) _Lexer_setError(cmp, __func__, format ,##__VA_ARGS__)
+void _Lexer_setError(Lexer* cmp, cstr context, cstr format, ...) __attribute__((__format__(__printf__, 3, 4)));
 
 typedef struct CodePos {
     u32 line; // 0 on error
@@ -43,5 +44,5 @@ typedef struct CodePos {
 #define CodePos_create(L, C) ((CodePos){ .line = L, .column = C })
 
 /// @param pos index in code buffer
-CodePos Compiler_getLineAndColumn(Compiler* cmp, u32 pos);
+CodePos Lexer_getLineAndColumn(Lexer* cmp, u32 pos);
 
diff --git a/src/compiler/compiler_internal.h b/src/compiler/compiler_internal.h
new file mode 100644
index 0000000..e69de29
diff --git a/src/compiler/parser.c b/src/compiler/parser.c
new file mode 100644
index 0000000..5de8c9d
--- /dev/null
+++ b/src/compiler/parser.c
@@ -0,0 +1,3 @@
+#include "compiler.h"
+
+List_define(DataDefinition);
diff --git a/src/compiler/token.c b/src/compiler/token.c
index 29ffecd..e5f7961 100644
--- a/src/compiler/token.c
+++ b/src/compiler/token.c
@@ -5,15 +5,19 @@ static cstr _TokenType_str[] = {
     "SingleLineComment",
     "MultiLineComment",
     "Label",
-    "Instruction",
-    "Argument",
+    "DataDefinition",
     "Number",
     "Char",
     "String",
+    "Instruction",
+    "Register",
+    "DataType",
+    "DataPointer",
+    "DataSize"
 };
 
 cstr TokenType_toString(TokenType t){
-    if(t >= sizeof(_TokenType_str) / sizeof(cstr))
+    if(t >= ARRAY_SIZE(_TokenType_str))
         return "!!INDEX_ERROR!!";
     return _TokenType_str[t];
 }
diff --git a/src/compiler/token.h b/src/compiler/token.h
index 8e3d744..a5fee2c 100644
--- a/src/compiler/token.h
+++ b/src/compiler/token.h
@@ -6,11 +6,15 @@ typedef enum TokenType {
     TokenType_SingleLineComment,
     TokenType_MultiLineComment,
     TokenType_Label,
-    TokenType_Instruction,
-    TokenType_Argument,
+    TOkenType_DataDefinition,
     TokenType_Number,
     TokenType_Char,
     TokenType_String,
+    TokenType_Instruction,
+    TokenType_Register,
+    TokenType_DataType,
+    TokenType_DataPointer,
+    TokenType_DataSize
 } TokenType;
 
 cstr TokenType_toString(TokenType t);
diff --git a/src/instructions/instructions.c b/src/instructions/instructions.c
index 9b96dbc..1431253 100644
--- a/src/instructions/instructions.c
+++ b/src/instructions/instructions.c
@@ -1,5 +1,19 @@
 #include "instructions.h"
 
+i32 NOP_impl(VM* vm);
+i32 PUSH_impl(VM* vm);
+i32 MOV_impl(VM* vm);
+i32 ADD_impl(VM* vm);
+i32 SUB_impl(VM* vm);
+i32 MUL_impl(VM* vm);
+i32 DIV_impl(VM* vm);
+i32 MOD_impl(VM* vm);
+i32 SYS_impl(VM* vm);
+i32 EXIT_impl(VM* vm);
+i32 JMP_impl(VM* vm);
+i32 CALL_impl(VM* vm);
+
+
 const Instruction instructions[] = {
     Instruction_construct(NOP),
     Instruction_construct(PUSH),
@@ -14,10 +28,9 @@ const Instruction instructions[] = {
     // Instruction_construct(JMP),
     // Instruction_construct(CALL),
 };
-const size_t instructions_count = sizeof(instructions)/sizeof(instructions[0]);
 
-const Instruction* NULLABLE(Instruction_getFromOpcode)(u8 opcode){
-    if(opcode >= instructions_count)
+const Instruction* Instruction_getFromOpcode(Opcode opcode){
+    if(opcode >= ARRAY_SIZE(instructions))
         return NULL;
     
     return instructions + opcode;
diff --git a/src/instructions/instructions.h b/src/instructions/instructions.h
index ba670b2..7f06caa 100644
--- a/src/instructions/instructions.h
+++ b/src/instructions/instructions.h
@@ -5,30 +5,32 @@
 ///@returns number of bytes read
 typedef i32 (*InstructionImplFunc_t)(VM* vm);
 
+typedef enum __attribute__((__packed__)) Opcode {
+    Opcode_NOP,
+    Opcode_PUSH,
+    Opcode_MOV,
+    Opcode_ADD,
+    Opcode_SUB,
+    Opcode_MUL,
+    Opcode_DIV,
+    Opcode_MOD,
+    Opcode_SYS,
+    Opcode_EXIT,
+} Opcode;
+
 typedef struct Instruction {
     cstr name;
     InstructionImplFunc_t implementation;
+    Opcode opcode;
 } Instruction;
 
 #define Instruction_construct(NAME) {\
     .name = #NAME, \
-    .implementation = NAME##_impl \
+    .implementation = NAME##_impl, \
+    .opcode = Opcode_##NAME\
 }
 
 /// @brief get instruction info from table
 /// @param opcode any byte
 /// @return ptr to struct or NULL
-const Instruction* NULLABLE(Instruction_getFromOpcode)(u8 opcode);
-
-i32 NOP_impl(VM* vm);
-i32 PUSH_impl(VM* vm);
-i32 MOV_impl(VM* vm);
-i32 ADD_impl(VM* vm);
-i32 SUB_impl(VM* vm);
-i32 MUL_impl(VM* vm);
-i32 DIV_impl(VM* vm);
-i32 MOD_impl(VM* vm);
-i32 SYS_impl(VM* vm);
-i32 EXIT_impl(VM* vm);
-i32 JMP_impl(VM* vm);
-i32 CALL_impl(VM* vm);
+const Instruction* NULLABLE(Instruction_getFromOpcode)(Opcode opcode);
diff --git a/src/std.h b/src/std.h
index dbdb070..bb63bfa 100644
--- a/src/std.h
+++ b/src/std.h
@@ -26,6 +26,8 @@ typedef u8 bool;
 
 typedef const char* cstr;
 
+#define ARRAY_SIZE(A) sizeof(A)/sizeof(A[0])
+
 #define __count_args( \
     a0, a1, a2, a3, a4, a5, a6, a7 , a8, a9, a10,a11,a12,a13,a14,a15, \
     a16,a17,a18,a19,a20,a21,a22,a23, a24,a25,a26,a27,a28,a29,a30,a31, \