diff --git a/README.md b/README.md
index 5120fc0..05103ab 100644
--- a/README.md
+++ b/README.md
@@ -7,6 +7,7 @@ Stack based virtual machine and assembly code compiler
 - Assembly
   - Stack operations (push & pop)
   - Arithmetics operations
+  - I/O operations
 
 ## Assembly documentation
 
@@ -28,6 +29,10 @@ Stack based virtual machine and assembly code compiler
   Removes two top values in stack and pushes integer part of division
 - **MOD**
   Removes two top values in stack and pushes modulo
+- **IN**
+  Inputs string with C I/O operators
+- **OUT**
+  Outputs string with C I/O operators
 
 ## TODO
 
diff --git a/command.c b/command.c
index d97a84e..f364f6c 100644
--- a/command.c
+++ b/command.c
@@ -8,4 +8,8 @@ cmd_desc_t cmd_desc[] = {
     {MUL, 0, "MUL"},
     {DIV, 0, "DIV"},
     {MOD, 0, "MOD"},
+#ifdef IO_OPERATIONS
+    {IN, 0, "IN"},
+    {OUT, 0, "OUT"},
+#endif
     {NONE, 0, "NONE"}}
diff --git a/command.h b/command.h
index dd340d0..1b0738c 100644
--- a/command.h
+++ b/command.h
@@ -10,6 +10,10 @@ enum command_e
   MUL,
   DIV,
   MOD,
+#ifdef IO_OPERATIONS
+  IN,
+  OUT,
+#endif
   NONE
 };
 
diff --git a/run.c b/run.c
index 90d400a..e843d1d 100644
--- a/run.c
+++ b/run.c
@@ -123,8 +123,45 @@ int exec(command_t cmd, stack_t *stack)
       return *res;
   }
   break;
+#ifdef IO_OPERATIONS
+  /**
+   * Inputs string with C I/O operators
+   */
+  case IN:
+  {
+    char input[512];
+    scanf("%s", &input);
+    int size = str_len(input);
+
+    for (int pos = size; size >= 0; size--)
+    {
+      stack_push(stack, input[pos], res);
+      if (res != NULL)
+        return *res;
+    }
+  }
+  break;
+  /**
+   * Outputs string with C I/O operators
+   */
+  case OUT:
+  {
+    char ch = stack_pop(stack, res);
+    if (res != NULL)
+      return *res;
+
+    while (ch != NULL)
+    {
+      putchar(ch);
+      ch = stack_pop(stack, res);
+      if (res != NULL)
+        return *res;
+    }
+  }
+  break;
+#endif
   default:
-    return -1;
+    return 1;
   }
 
   return 0;
diff --git a/run.h b/run.h
index 7ee3f5f..6107be6 100644
--- a/run.h
+++ b/run.h
@@ -3,6 +3,11 @@
 
 #include "./stack.h"
 #include "./command.h"
+#include "./utils.h"
+
+#ifdef IO_OPERATIONS
+#include <stdio.h>
+#endif
 
 int run(command_t **buff, stack_t *stack);
 int exec(command_t cmd, stack_t *stack);
diff --git a/stack.c b/stack.c
index f67d285..3c72d6c 100644
--- a/stack.c
+++ b/stack.c
@@ -30,12 +30,12 @@ int stack_push(stack_t *stack, int value, int *result)
 
   if (stack->cursor > stack->size - 1)
   {
-    *result = 1;
+    *result = 2;
     return *result;
   }
 
   stack->mem[stack->cursor + 1] = value;
-  stack->cursor += 1;
+  stack->cursor++;
 
   return 0;
 }
@@ -51,7 +51,7 @@ int stack_pop(stack_t *stack, int *result)
   }
 
   int value = stack->mem[stack->cursor];
-  stack->cursor -= 1;
+  stack->cursor--;
 
   return value;
 }
diff --git a/utils.c b/utils.c
new file mode 100644
index 0000000..5e6c8ae
--- /dev/null
+++ b/utils.c
@@ -0,0 +1,11 @@
+#include "./utils.h"
+
+int str_len(char str[])
+{
+  int pos = 0;
+
+  while (str[pos] != NULL)
+    pos++;
+
+  return pos;
+}
\ No newline at end of file
diff --git a/utils.h b/utils.h
new file mode 100644
index 0000000..a733f8b
--- /dev/null
+++ b/utils.h
@@ -0,0 +1,7 @@
+#ifndef UTILS_H
+
+#include <stdlib.h>
+
+int str_len(char str[]);
+
+#endif
\ No newline at end of file