diff --git a/byterun/include/interpreter.h b/byterun/include/interpreter.h
index aae9ad99e..2a87ac2fe 100644
--- a/byterun/include/interpreter.h
+++ b/byterun/include/interpreter.h
@@ -2,4 +2,4 @@
 
 #include "parser.h"
 
-void run(bytefile *bf, int argc, char **argv);
+void run(uint mod_id, int argc, char **argv);
diff --git a/byterun/include/module_manager.h b/byterun/include/module_manager.h
index f4dadd8d7..70d643bc4 100644
--- a/byterun/include/module_manager.h
+++ b/byterun/include/module_manager.h
@@ -5,9 +5,9 @@
 #include "utils.h"
 
 struct ModSearchResult {
-  ssize_t symbol_offset; // < 0 => not found
+  size_t symbol_offset;
   uint32_t mod_id;
-  bytefile *mod_file;
+  bytefile *mod_file; // = NULL => not found
 };
 
 void mod_add_search_path(const char *path);
@@ -16,4 +16,6 @@ bytefile *mod_get(uint32_t id);
 
 int32_t mod_load(const char *name); // < 0 => not found
 
+uint32_t mod_add(bytefile *module);
+
 struct ModSearchResult mod_search_pub_symbol(const char *name);
diff --git a/byterun/include/stack.h b/byterun/include/stack.h
index b58de8ac5..8aa99b7fe 100644
--- a/byterun/include/stack.h
+++ b/byterun/include/stack.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include "../../runtime/gc.h"
+#include "module_manager.h"
 #include "runtime_externs.h"
 #include "types.h"
 #include "utils.h"
@@ -134,14 +135,14 @@ static inline void s_rotate_n(size_t n) {
 
 // ------ functions ------
 
-// |> param_0 ... param_n | frame[ ret rp prev_fp &params &locals &end
+// |> param_0 ... param_n | frame[ ret rp prev_fp ... &params &locals &end
 // ]
 // |> local_0 ... local_m |> | ...
 //
 // where |> defines corresponding frame pointer, | is stack pointer
 // location before / after new frame added
-static inline void s_enter_f(char *rp, bool is_closure_call, auint args_sz,
-                             auint locals_sz) {
+static inline void s_enter_f(char *rp, aint ret_module_id, bool is_closure_call,
+                             auint args_sz, auint locals_sz) {
 #ifdef DEBUG_VERSION
   printf("-> %i args sz\n", args_sz);
   printf("-> %i locals sz\n", locals_sz);
@@ -169,6 +170,7 @@ static inline void s_enter_f(char *rp, bool is_closure_call, auint args_sz,
       .ret = NULL, // field in frame itself
       .rp = rp,
       .prev_fp = (void **)s.fp,
+      .ret_module_box = BOX(ret_module_id),
       .args_sz_box = BOX(args_sz),
       .locals_sz_box = BOX(locals_sz),
   };
@@ -207,6 +209,10 @@ static inline void s_exit_f() {
   }
 
   s.ip = frame.rp;
+
+  s.current_module_id = UNBOX(frame.ret_module_box);
+  s.bf = mod_get(s.current_module_id);
+  // TODO: return to ret_module
 }
 
 static inline void print_stack() {
diff --git a/byterun/include/types.h b/byterun/include/types.h
index a3cba0592..c9067c048 100644
--- a/byterun/include/types.h
+++ b/byterun/include/types.h
@@ -22,13 +22,14 @@ static const size_t MAX_ARRAY_SIZE = 0x11111110;
 // ------ Frame ------
 
 struct Frame {
-  void *closure;      // where closure value stored if needed
-  void *ret;          // store returned value [gc pointer]
-  char *rp;           // ret instruction pointer [not gc pointer]
-  void **prev_fp;     // ret function frame pointer [boxed value, not gc
-                      // pointer]
-  aint args_sz_box;   // store arguments [boxed value, not gc pointer]
-  aint locals_sz_box; // store locals [boxed value, not gc pointer]
+  void *closure;       // where closure value stored if needed
+  void *ret;           // store returned value [gc pointer]
+  char *rp;            // ret instruction pointer [not gc pointer]
+  void **prev_fp;      // ret function frame pointer [boxed value, not gc
+                       // pointer]
+  aint ret_module_box; // module to return [boxed value, not gc pointer]
+  aint args_sz_box;    // store arguments [boxed value, not gc pointer]
+  aint locals_sz_box;  // store locals [boxed value, not gc pointer]
 };
 
 // NOTE: stack is [top -> bottom]
@@ -60,14 +61,18 @@ struct State {
 
   bool is_closure_call;
 
+  uint current_module_id;
+  uint call_module_id;
+
   char *ip;       // instruction pointer
   char *instr_ip; // poiter to current instruction
   char *call_ip;  // prev instruction pointer (to remember jmp locations)
 };
 
-void construct_state(bytefile *bf, struct State *s, void **stack);
+void construct_state(uint mod_id, struct State *s, void **stack);
 void cleanup_state(struct State *state);
 
+// TODO: print current mod id
 static inline void s_failure(struct State *s, const char *msg) {
   exec_failure(read_cmd(s->instr_ip), s->current_line,
                s->instr_ip - s->bf->code_ptr, msg);
diff --git a/byterun/src/cli.c b/byterun/src/cli.c
index 3b22af2da..5ed2a26c5 100644
--- a/byterun/src/cli.c
+++ b/byterun/src/cli.c
@@ -1,4 +1,5 @@
 #include "interpreter.h"
+#include "module_manager.h"
 #include "parser.h"
 #include "utils.h"
 #include "../../runtime/runtime.h"
@@ -9,15 +10,15 @@ int main(int argc, char** argv) {
   }
 
   bytefile *f = read_file(argv[2]);
+  uint main_mod_id = mod_add(f);
   if (strcmp(argv[1], "-i") == 0) {
-    run(f, argc - 1, argv + 1);
+    run(main_mod_id, argc - 1, argv + 1); // TODO: init all modules, execute all prev. modules
   } else if (strcmp(argv[1], "-p") == 0) {
     dump_file (stdout, f);
   } else {
     failure("undefined execution mode. Execution mode should be -i (interpret) or -p (print)\n");
   }
 
-  free(f->global_ptr);
   free(f);
 
   return 0;
diff --git a/byterun/src/interpreter.c b/byterun/src/interpreter.c
index 4cde7f572..039695837 100644
--- a/byterun/src/interpreter.c
+++ b/byterun/src/interpreter.c
@@ -3,6 +3,7 @@
 #include "../../runtime/gc.h"
 #include "../../runtime/runtime.h"
 
+#include "module_manager.h"
 #include "runtime_externs.h"
 #include "stack.h"
 #include "types.h"
@@ -37,10 +38,17 @@ static inline const char *ip_read_string(char **ip) {
 
 const size_t BUFFER_SIZE = 1000;
 
-void run(bytefile *bf, int argc, char **argv) {
+void init_stack(int argc, char **argv) {} // TODO
+
+void init_mod_rec(uint mod_id) {} // TODO
+
+void run(uint mod_id, int argc, char **argv) { // TODO: remove mod init and stack init
   size_t stack[STACK_SIZE];
   void *buffer[BUFFER_SIZE];
-  construct_state(bf, &s, (void **)stack);
+  construct_state(
+      mod_id, &s,
+      (void **)
+          stack); // TODO: separate on each module part and part for all run
 
 #ifdef DEBUG_VERSION
   printf("--- interpreter run ---\n");
@@ -65,11 +73,11 @@ void run(bytefile *bf, int argc, char **argv) {
   do {
     bool call_happened = false;
 
-    if (s.ip >= bf->code_ptr + bf->code_size) {
+    if (s.ip >= s.bf->code_ptr + s.bf->code_size) {
       s_failure(&s, "instruction pointer is out of range (>= size)");
     }
 
-    if (s.ip < bf->code_ptr) {
+    if (s.ip < s.bf->code_ptr) {
       s_failure(&s, "instruction pointer is out of range (< 0)");
     }
 
@@ -171,10 +179,10 @@ void run(bytefile *bf, int argc, char **argv) {
       case CMD_BASIC_JMP: { // JMP 0x%.8x
         uint jmp_p = ip_read_int(&s.ip);
 
-        if (jmp_p >= bf->code_size) {
+        if (jmp_p >= s.bf->code_size) {
           s_failure(&s, "jump out of file");
         }
-        s.ip = bf->code_ptr + jmp_p;
+        s.ip = s.bf->code_ptr + jmp_p;
         break;
       }
 
@@ -246,11 +254,11 @@ void run(bytefile *bf, int argc, char **argv) {
       case CMD_CTRL_CJMPz: { // CJMPz 0x%.8x
         uint jmp_p = ip_read_int(&s.ip);
 
-        if (jmp_p >= bf->code_size) {
+        if (jmp_p >= s.bf->code_size) {
           s_failure(&s, "jump out of file");
         }
         if (UNBOX(s_pop_i()) == 0) {
-          s.ip = bf->code_ptr + jmp_p;
+          s.ip = s.bf->code_ptr + jmp_p;
         }
         break;
       }
@@ -258,11 +266,11 @@ void run(bytefile *bf, int argc, char **argv) {
       case CMD_CTRL_CJMPnz: { // CJMPnz  0x%.8x
         uint jmp_p = ip_read_int(&s.ip);
 
-        if (jmp_p >= bf->code_size) {
+        if (jmp_p >= s.bf->code_size) {
           s_failure(&s, "jump out of file");
         }
         if (UNBOX(s_pop_i()) != 0) {
-          s.ip = bf->code_ptr + jmp_p;
+          s.ip = s.bf->code_ptr + jmp_p;
         }
         break;
       }
@@ -273,8 +281,8 @@ void run(bytefile *bf, int argc, char **argv) {
         if (s.fp != NULL && s.call_ip == NULL) {
           s_failure(&s, "begin should only be called after call");
         }
-        s_enter_f(s.call_ip /*ip from call*/, s.is_closure_call, args_sz,
-                  locals_sz);
+        s_enter_f(s.call_ip /*ip from call*/, s.call_module_id,
+                  s.is_closure_call, args_sz, locals_sz);
         break;
       }
 
@@ -285,8 +293,8 @@ void run(bytefile *bf, int argc, char **argv) {
         if (s.fp != NULL && s.call_ip == NULL) {
           s_failure(&s, "begin should only be called after call");
         }
-        s_enter_f(s.call_ip /*ip from call*/, s.is_closure_call, args_sz,
-                  locals_sz);
+        s_enter_f(s.call_ip /*ip from call*/, s.call_module_id,
+                  s.is_closure_call, args_sz, locals_sz);
         break;
       }
 
@@ -302,10 +310,10 @@ void run(bytefile *bf, int argc, char **argv) {
               var_by_category(to_var_category(l), ip_read_int(&s.ip));
           s_push(*var_ptr);
         }
-        if (call_offset >= bf->code_size) {
+        if (call_offset >= s.bf->code_size) {
           s_failure(&s, "jump out of file");
         }
-        s_push(bf->code_ptr + call_offset);
+        s_push(s.bf->code_ptr + call_offset);
 
         void *closure = Bclosure((aint *)__gc_stack_top, args_count);
 
@@ -320,6 +328,7 @@ void run(bytefile *bf, int argc, char **argv) {
         call_happened = true;
         s.is_closure_call = true;
         s.call_ip = s.ip;
+        s.call_module_id = s.current_module_id;
 
         s.ip = Belem(*s_nth(args_count), BOX(0)); // use offset instead ??
         break;
@@ -332,11 +341,12 @@ void run(bytefile *bf, int argc, char **argv) {
         call_happened = true;
         s.is_closure_call = false;
         s.call_ip = s.ip;
+        s.call_module_id = s.current_module_id;
 
-        if (call_p >= bf->code_size) {
+        if (call_p >= s.bf->code_size) {
           s_failure(&s, "jump out of file");
         }
-        s.ip = bf->code_ptr + call_p;
+        s.ip = s.bf->code_ptr + call_p;
         break;
       }
 
@@ -370,19 +380,27 @@ void run(bytefile *bf, int argc, char **argv) {
         break;
 
       case CMD_CTRL_CALLF: { // CALLF %s %d // call external function
-        const char* call_func = ip_read_string(&s.ip);
+        const char *call_func_name = ip_read_string(&s.ip);
         ip_read_int(&s.ip); // args count
 
         // TODO: jump to other module, save ret module
+        struct ModSearchResult func = mod_search_pub_symbol(call_func_name);
+        if (func.mod_file == NULL) {
+          s_failure(&s, "external function not found");
+        }
 
-        // call_happened = true;
-        // s.is_closure_call = false;
-        // s.call_ip = s.ip;
+        call_happened = true;
+        s.is_closure_call = false;
+        s.call_ip = s.ip;
+        s.call_module_id = s.current_module_id;
 
-        // if (call_p >= bf->code_size) {
-        //   s_failure(&s, "jump out of file");
-        // }
-        // s.ip = bf->code_ptr + call_p;
+        s.current_module_id = func.mod_id;
+        s.bf = func.mod_file;
+
+        if (func.symbol_offset >= s.bf->code_size) {
+          s_failure(&s, "jump out of file");
+        }
+        s.ip = s.bf->code_ptr + func.symbol_offset;
         break;
       }
 
@@ -452,10 +470,9 @@ void run(bytefile *bf, int argc, char **argv) {
         }
 
         // s_rotate_n(elem_count);
-        void *array =
-            Barray((aint *)opr_buffer,
-                   BOX(elem_count)); // NOTE: not shure if elems should be
-                                     // added
+        void *array = Barray((aint *)opr_buffer,
+                             BOX(elem_count)); // NOTE: not shure if elems
+                                               // should be added
 
         // void *array = Barray((aint *)s_peek(), BOX(elem_count));
         s_push(array);
@@ -474,6 +491,7 @@ void run(bytefile *bf, int argc, char **argv) {
     if (!call_happened) {
       s.is_closure_call = false;
       s.call_ip = NULL;
+      s.call_module_id = 0;
     }
 
     if (s.fp == NULL) {
diff --git a/byterun/src/module_manager.cpp b/byterun/src/module_manager.cpp
index fba0b624e..2044a2dc6 100644
--- a/byterun/src/module_manager.cpp
+++ b/byterun/src/module_manager.cpp
@@ -1,3 +1,4 @@
+#include <optional>
 extern "C" {
 #include "module_manager.h"
 #include "parser.h"
@@ -23,8 +24,8 @@ struct ModuleManager {
 
 static ModuleManager manager;
 
-uint32_t path_mod_load(const char *name, std::filesystem::path &&path) {
-  bytefile *module = read_file(path.c_str());
+uint32_t mod_add_impl(bytefile *module,
+                      std::optional<const char *> name = std::nullopt) {
   uint32_t id = manager.modules.size();
   manager.modules.push_back(module);
   for (size_t i = 0; i < module->public_symbols_number; ++i) {
@@ -37,9 +38,16 @@ uint32_t path_mod_load(const char *name, std::filesystem::path &&path) {
       failure("public symbol loaded more then once\n");
     }
   }
-  manager.loaded_modules.insert({name, id});
+  if (name) {
+    manager.loaded_modules.insert({*name, id});
+  }
   return id;
 }
+
+uint32_t path_mod_load(const char *name, std::filesystem::path &&path) {
+  bytefile *module = read_file(path.c_str());
+  return mod_add_impl(module, name);
+}
 extern "C" {
 
 void mod_add_search_path(const char *path) {
@@ -85,14 +93,16 @@ int32_t mod_load(const char *name) {
   return -1;
 }
 
+uint32_t mod_add(bytefile *module) { return mod_add_impl(module); }
+
 ModSearchResult mod_search_pub_symbol(const char *name) {
   auto it = manager.public_symbols_mods.find(name);
   if (it == manager.public_symbols_mods.end()) {
-    return {.symbol_offset = -1, .mod_id = 0, .mod_file = nullptr};
+    return {.symbol_offset = 0, .mod_id = 0, .mod_file = NULL};
   }
 
   return {
-      .symbol_offset = (int32_t)it->second.offset,
+      .symbol_offset = it->second.offset,
       .mod_id = it->second.mod_id,
       .mod_file = mod_get(it->second.mod_id),
   };
diff --git a/byterun/src/parser.c b/byterun/src/parser.c
index 02c9ad4dc..658090f06 100644
--- a/byterun/src/parser.c
+++ b/byterun/src/parser.c
@@ -65,7 +65,10 @@ bytefile* read_file (const char *fname) {
   file->imports_ptr  = (int*) file->buffer;
   file->public_ptr  = (int*) (file->buffer + imports_size);
   file->code_ptr    = &file->string_ptr [file->stringtab_size];
-  file->global_ptr  = (int*) calloc (file->global_area_size, sizeof (int));
+
+  // is allocated on module run on stack
+  file->global_ptr = NULL;
+  // file->global_ptr  = (int*) calloc (file->global_area_size, sizeof (int));
 
   file->code_size = size - strings_buffer_offset - file->stringtab_size;
 
diff --git a/byterun/src/types.c b/byterun/src/types.c
index b6772142c..b1c211ba4 100644
--- a/byterun/src/types.c
+++ b/byterun/src/types.c
@@ -1,5 +1,6 @@
 #include "types.h"
 
+#include "module_manager.h"
 #include "stack.h"
 #include "utils.h"
 #include "parser.h"
@@ -11,12 +12,14 @@ extern size_t __gc_stack_top, __gc_stack_bottom;
 
 // --- State ---
 
-static void init_state(bytefile *bf, struct State* s, void** stack) {
+static void init_state(uint mod_id, struct State* s, void** stack) {
   s->stack = stack;
-  s->bf = bf;
+  s->bf = mod_get(mod_id);
   s->is_closure_call = false;
-  s->ip = bf->code_ptr;
-  s->instr_ip = bf->code_ptr;
+  s->current_module_id = mod_id;
+  s->call_module_id = 0; // TODO: ??
+  s->ip = s->bf->code_ptr;
+  s->instr_ip = s->bf->code_ptr;
   s->call_ip = NULL;
   s->current_line = 0;
 
@@ -30,13 +33,14 @@ static void init_state(bytefile *bf, struct State* s, void** stack) {
   s->fp = NULL;
 }
 
-void construct_state(bytefile *bf, struct State* s, void** stack) {
+void construct_state(uint mod_id, struct State* s, void** stack) {
   __init();
-  init_state(bf, s, stack);
+  init_state(mod_id, s, stack);
   __gc_stack_bottom = (size_t)(s->stack + STACK_SIZE);
   __gc_stack_top = __gc_stack_bottom;
 
-  s_pushn_nil(bf->global_area_size);
+  s_pushn_nil(s->bf->global_area_size); // TODO: move to run, do for each module
+  s->bf->global_ptr = (void*)__gc_stack_top;
 
 #ifdef DEBUG_VERSION
   print_stack(s);