diff --git a/cstack.c b/cstack.c
index 72e36b4..5309197 100644
--- a/cstack.c
+++ b/cstack.c
@@ -1,42 +1,203 @@
 #include "cstack.h"
 #include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include <limits.h>
+#include <assert.h>
 
-#define UNUSED(VAR) (void)(VAR)
+#define RESULT_OK 0
+#define RESULT_NOT_OK 1
+#define INVALID_HANDLER -1
+#define INITIAL_SIZE 10
+
+typedef struct node
+{
+    struct node *prev;
+    unsigned int size;
+    char data[0];
+} node;
+
+typedef struct stack
+{
+    node *top;
+    unsigned int size;
+} stack;
+
+typedef struct stack_entry
+{
+    int valid;
+    stack stack;
+} stack_entry;
+
+typedef struct stack_entries_table
+{
+    hstack_t size;
+    stack_entry *entries;
+} stack_entries_table;
+
+stack_entries_table stacks = {0u, NULL};
+
+int allocate_table(void)
+{
+    assert(!stacks.entries);
+    stacks.entries = calloc(INITIAL_SIZE, sizeof(stack_entry));
+    if (stacks.entries)
+        stacks.size = INITIAL_SIZE;
+    else
+    {
+        stacks.entries = calloc(1, sizeof(stack_entry));
+        if (stacks.entries)
+            stacks.size = 1;
+        else
+            return RESULT_NOT_OK;
+    }
+    return RESULT_OK;
+}
+
+void reallocate_table(void)
+{
+    assert(stacks.entries);
+    hstack_t new_size = stacks.size * 2;
+    stack_entry *new_array = calloc(new_size, sizeof(stack_entry));
+
+    if (!new_array)
+    {
+        new_size = stacks.size + 1;
+        new_array = calloc(new_size, sizeof(stack_entry));
+    }
+
+    if (new_array)
+    {
+        memcpy(new_array, stacks.entries, stacks.size * sizeof(stack_entry));
+        free(stacks.entries);
+        stacks.entries = new_array;
+        stacks.size = new_size;
+    }
+}
+
+void deallocate_table(void)
+{
+    free(stacks.entries);
+    stacks.entries = NULL;
+    stacks.size = 0;
+}
+
+int is_table_empty(void)
+{
+    for (hstack_t index = 0; index < stacks.size; ++index)
+    {
+        if (stacks.entries[index].valid)
+            return RESULT_NOT_OK;
+    }
+    return RESULT_OK;
+}
+
+hstack_t get_free_index(void)
+{
+    hstack_t index = 0;
+    for (; index < stacks.size && stacks.entries[index].valid; ++index)
+        ;
+    return index;
+}
 
 hstack_t stack_new(void)
 {
-    return -1;
+    if (!stacks.entries)
+        if (allocate_table() != RESULT_OK)
+            return INVALID_HANDLER;
+
+    hstack_t index = get_free_index();
+
+    if (index >= stacks.size)
+        reallocate_table();
+
+    if (index < stacks.size)
+    {
+        stacks.entries[index].valid = 1;
+        return index;
+    }
+    return INVALID_HANDLER;
 }
 
 void stack_free(const hstack_t hstack)
 {
-    UNUSED(hstack);
+    if (stack_valid_handler(hstack) != RESULT_OK)
+        return;
+
+    stack *stack = &stacks.entries[hstack].stack;
+    node *cur_node = stack->top;
+
+    stacks.entries[hstack].valid = 0;
+    stack->top = NULL;
+    stack->size = 0;
+
+    node *prev_node;
+    while (cur_node)
+    {
+        prev_node = cur_node->prev;
+        free(cur_node);
+        cur_node = prev_node;
+    }
+
+    if (is_table_empty() == RESULT_OK)
+        deallocate_table();
 }
 
 int stack_valid_handler(const hstack_t hstack)
 {
-    UNUSED(hstack);
-    return 1;
+    if (hstack >= 0 && hstack < stacks.size && stacks.entries[hstack].valid)
+        return RESULT_OK;
+    return RESULT_NOT_OK;
 }
 
 unsigned int stack_size(const hstack_t hstack)
 {
-    UNUSED(hstack);
+    if (stack_valid_handler(hstack) == RESULT_OK)
+        return stacks.entries[hstack].stack.size;
     return 0;
 }
 
-void stack_push(const hstack_t hstack, const void* data_in, const unsigned int size)
+void stack_push(const hstack_t hstack, const void *data_in, const unsigned int size)
 {
-    UNUSED(hstack);
-    UNUSED(data_in);
-    UNUSED(size);
+    if (!data_in || !size || stack_valid_handler(hstack) != RESULT_OK)
+        return;
+
+    stack *stack = &stacks.entries[hstack].stack;
+    if (stack->size == UINT_MAX)
+        return;
+
+    node *new_node = malloc(sizeof(node) + size);
+    if (!new_node)
+        return;
+
+    new_node->prev = stack->top;
+    new_node->size = size;
+    memcpy(new_node->data, data_in, size);
+
+    stack->top = new_node;
+    stack->size += 1;
 }
 
-unsigned int stack_pop(const hstack_t hstack, void* data_out, const unsigned int size)
+unsigned int stack_pop(const hstack_t hstack, void *data_out, const unsigned int size)
 {
-    UNUSED(hstack);
-    UNUSED(data_out);
-    UNUSED(size);
-    return 0;
-}
+    if (!data_out || !size || stack_valid_handler(hstack) != RESULT_OK)
+        return 0;
 
+    stack *stack = &stacks.entries[hstack].stack;
+    node *cur_node = stack->top;
+
+    if (!cur_node)
+        return 0;
+    assert(stack->size > 0);
+
+    unsigned int data_size = cur_node->size;
+    if (data_size > size)
+        return 0;
+
+    stack->top = cur_node->prev;
+    stack->size -= 1;
+
+    memcpy(data_out, cur_node->data, data_size);
+    free(cur_node);
+    return data_size;
+}
diff --git a/test.cpp b/test.cpp
index 657219b..5881483 100644
--- a/test.cpp
+++ b/test.cpp
@@ -124,3 +124,100 @@ TEST_F(ModifyTests, SeveralPushPop)
     EXPECT_THAT(data_out, ::testing::ElementsAre(2, 1, 0));
 }
 
+TEST(CustomTests, NewPushFreePop)
+{
+    const size_t count = 10;
+    hstack_t stacks[count] = {-1};
+    for (size_t i = 0; i < count; ++i)
+    {
+        stacks[i] = stack_new();
+        EXPECT_EQ(stack_valid_handler(stacks[i]), 0);
+        EXPECT_EQ(stack_size(stacks[i]), 0u);
+        int data_out = 1;
+        EXPECT_EQ(stack_pop(stacks[i], &data_out, sizeof(data_out)), 0u);
+        EXPECT_EQ(data_out, 1);
+        EXPECT_EQ(stack_valid_handler(stacks[i]), 0);
+        EXPECT_EQ(stack_size(stacks[i]), 0u);
+    }
+    for (size_t i = 0; i < count; ++i)
+    {
+        EXPECT_EQ(stack_valid_handler(stacks[i]), 0);
+        EXPECT_EQ(stack_size(stacks[i]), 0u);
+        const int data_in = 1;
+        stack_push(stacks[i], &data_in, sizeof(data_in));
+        EXPECT_EQ(stack_valid_handler(stacks[i]), 0);
+        EXPECT_EQ(stack_size(stacks[i]), 1u);
+    }
+    for (size_t i = 1; i < count; ++i)
+    {
+        stack_free(stacks[i]);
+        EXPECT_EQ(stack_valid_handler(stacks[i]), 1);
+    }
+    for (size_t i = 1; i < count; ++i)
+    {
+        stacks[i] = stack_new();
+        EXPECT_EQ(stack_valid_handler(stacks[i]), 0);
+        EXPECT_EQ(stack_size(stacks[i]), 0u);
+        int data_out = 0;
+        EXPECT_EQ(stack_pop(stacks[i], &data_out, sizeof(data_out)), 0u);
+        EXPECT_EQ(data_out, 0);
+        EXPECT_EQ(stack_valid_handler(stacks[i]), 0);
+        EXPECT_EQ(stack_size(stacks[i]), 0u);
+    }
+    for (size_t i = 0; i < count; ++i)
+    {
+        stack_free(stacks[i]);
+        EXPECT_EQ(stack_valid_handler(stacks[i]), 1);
+    }
+}
+
+TEST(CustomTests, FreeAfterFree)
+{
+    const size_t count = 10;
+    hstack_t stacks[count] = {-1};
+    for (size_t i = 0; i < count; ++i)
+    {
+        stacks[i] = stack_new();
+        EXPECT_EQ(stack_valid_handler(stacks[i]), 0);
+        EXPECT_EQ(stack_size(stacks[i]), 0u);
+    }
+    for (size_t i = 1; i < count; ++i)
+    {
+        stack_free(stacks[i]);
+        EXPECT_EQ(stack_valid_handler(stacks[i]), 1);
+    }
+    for (size_t i = 0; i < count; ++i)
+    {
+        stack_free(stacks[i]);
+        EXPECT_EQ(stack_valid_handler(stacks[i]), 1);
+    }
+    for (size_t i = 0; i < count; ++i)
+    {
+        stack_free(stacks[i]);
+        EXPECT_EQ(stack_valid_handler(stacks[i]), 1);
+    }
+}
+
+TEST(CustomTests, BigSizeStack)
+{
+    const char example = 'a';
+    const size_t limit = 100000;
+    hstack_t stack = stack_new();
+    EXPECT_EQ(stack_valid_handler(stack), 0);
+    for (unsigned int i = 0; i < limit; ++i)
+    {
+        char c = example;
+        stack_push(stack, &c, sizeof(c));
+        EXPECT_EQ(stack_size(stack), i + 1);
+    }
+    for (unsigned int i = 0; i < limit; ++i)
+    {
+        char c = 0;
+        unsigned int size = stack_pop(stack, &c, sizeof(c));
+        EXPECT_EQ(size, sizeof(c));
+        EXPECT_EQ(c, example);
+        EXPECT_EQ(stack_size(stack), limit - (i + 1));
+    }
+    stack_free(stack);
+    EXPECT_EQ(stack_valid_handler(stack), 1);
+}
\ No newline at end of file