diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..81558dd
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+obj
+main
+tail
+test*
+chatgpt.c
diff --git a/.vscode/launch.json b/.vscode/launch.json
new file mode 100644
index 0000000..be950bf
--- /dev/null
+++ b/.vscode/launch.json
@@ -0,0 +1,17 @@
+{
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "type": "lldb",
+            "request": "launch",
+            "name": "Debug",
+            "program": "${workspaceFolder}/main",
+            "args": ["./src/tail.c", "-n", "20"],
+            "cwd": "${workspaceFolder}",
+            "preLaunchTask": "Makefile",
+            "env": {
+                "ASAN_OPTIONS": "detect_leaks=0"
+            }
+        }
+    ]
+}
diff --git a/.vscode/settings.json b/.vscode/settings.json
new file mode 100644
index 0000000..9cf8272
--- /dev/null
+++ b/.vscode/settings.json
@@ -0,0 +1,9 @@
+{
+    "makefile.launchConfigurations": [
+        {
+            "cwd": "/home/user/coding/ijc/2hw",
+            "binaryPath": "/home/user/coding/ijc/2hw/tail",
+            "binaryArgs": []
+        }
+    ]
+}
diff --git a/.vscode/tasks.json b/.vscode/tasks.json
new file mode 100644
index 0000000..2385146
--- /dev/null
+++ b/.vscode/tasks.json
@@ -0,0 +1,10 @@
+{
+    "version": "2.0.0",
+    "tasks": [
+        {
+            "label": "Makefile",
+            "type": "shell",
+            "command": "make",
+        }
+    ]
+}
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..59591be
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,28 @@
+CC := clang
+CFLAGS := -g -Wall -std=c11 -pedantic -Wextra -O3 -fsanitize=address
+CREATEDIR := $(shell mkdir -p obj)
+
+.PHONY: all
+all: tail #wordcount wordcount-dynamic
+# a knihovny "libhtab.a", "libhtab.so
+
+tail: obj/tail.o
+	$(CC) $(CFLAGS) -lm $^ -o $@
+
+#												\
+wordcount: obj/wordcount.o obj/htab.o			\
+	$(CC) $(CFLAGS) -lm $^ -o $@				\
+												\
+wordcount-dynamic: obj/wordcount.o obj/htab.o	\
+	$(CC) $(CFLAGS) -lm $^ -o $@
+
+
+obj/tail.o: src/tail.c
+
+obj/%.o: src/%.c
+	$(CC) $(CFLAGS) $< -c -o $@
+
+
+.PHONY: clean
+clean:
+	-rm -r ./obj/ primes primes-i steg-decode
diff --git a/src/htab.c b/src/htab.c
new file mode 100644
index 0000000..605c095
--- /dev/null
+++ b/src/htab.c
@@ -0,0 +1,107 @@
+#include <stdio.h>
+#include "htab.h"
+
+struct htab_item {
+    struct htab_pair data;
+    struct htab_item* next;
+};
+
+struct htab {
+    size_t size;
+    size_t arr_size;
+    struct htab_item** arr_ptr;
+};
+
+size_t htab_hash_function(htab_key_t str) {
+    unsigned h = 0;     // musí mít 32 bitů
+    const unsigned char *p;
+    for(p = (const unsigned char*)str; *p != '\0'; p++)
+        h = 65599 * h + *p;
+    return h;
+}
+
+htab_t *htab_init(const size_t n) {
+    htab_t *t = malloc(sizeof(htab_t));
+    if (!t) {
+        fputs("couldn't allocate memory for hash tab", stderr);
+        return NULL;
+    }
+
+    t->arr_ptr = malloc(n * sizeof(struct htab_item*));
+    if (!t->arr_ptr) {
+        fputs("couldn't allocate memory for array of pointers", stderr);
+        free(t);
+        return NULL;
+    }
+
+    t->size = 0;
+    t->arr_size = n;
+
+    return t;
+}
+
+size_t htab_size(const htab_t *t) {
+    return t->size;
+}
+
+size_t htab_bucket_count(const htab_t *t) {
+    return t->arr_size;
+}
+
+htab_pair_t *htab_find(const htab_t *t, htab_key_t key) {
+    size_t index = (htab_hash_function(key) % t->arr_size);
+    struct htab_item* curr_item = t->arr_ptr[index];
+    while (curr_item->next != NULL) {
+        if (strcmp(curr_item->data.key, key) == 0) {
+            return &(curr_item->data);
+        }
+
+        curr_item = curr_item->next;
+    }
+    return NULL;
+}
+
+htab_pair_t *htab_lookup_add(htab_t *t, htab_key_t key) {
+    htab_pair_t *return_pair;
+    if (return_pair = htab_find(t, key)) {
+        return_pair->value++;
+        return return_pair;
+    }
+
+    struct htab_item *item_to_add = malloc(sizeof(struct htab_item));
+    if (!item_to_add) {
+        fputs("couldn't allocate memory for item to add", stderr);
+        return NULL;
+    }
+    struct htab_pair data_to_add = {.key = malloc(sizeof(key)), .value = 1};
+    if (!data_to_add.key) {
+        fputs("couldn't allocate memory for key in item to add", stderr);
+        free(item_to_add);
+        return NULL;
+    }
+    data_to_add.key = key;
+    item_to_add->data = data_to_add;
+
+    size_t index = (htab_hash_function(key) % t->arr_size);
+    struct htab_item* curr_item = t->arr_ptr[index];
+    while (curr_item->next != NULL) {
+        curr_item = curr_item->next;
+    }
+
+    curr_item->next = item_to_add;
+}
+
+bool htab_erase(htab_t *t, htab_key_t key) {
+}
+
+void htab_for_each(const htab_t *t, void (*f)(htab_pair_t *data)) {
+}
+
+void htab_clear(htab_t *t) {
+}
+
+void htab_free(htab_t *t) {
+}
+
+void htab_statistics(const htab_t *t) {
+}
diff --git a/src/htab.h b/src/htab.h
new file mode 100644
index 0000000..f4846bb
--- /dev/null
+++ b/src/htab.h
@@ -0,0 +1,49 @@
+// htab.h -- rozhraní knihovny htab (řešení IJC-DU2)
+// Licence: žádná (Public domain)
+
+// následující řádky zabrání násobnému vložení:
+#ifndef HTAB_H__
+#define HTAB_H__
+
+#include <string.h>     // size_t
+#include <stdbool.h>    // bool
+
+// Tabulka:
+struct htab;    // neúplná deklarace struktury - uživatel nevidí obsah
+typedef struct htab htab_t;     // typedef podle zadání
+
+// Typy:
+typedef const char * htab_key_t;        // typ klíče
+typedef int htab_value_t;               // typ hodnoty
+
+// Dvojice dat v tabulce:
+typedef struct htab_pair {
+    htab_key_t    key;          // klíč
+    htab_value_t  value;        // asociovaná hodnota
+} htab_pair_t;                  // typedef podle zadání
+
+// Rozptylovací (hash) funkce (stejná pro všechny tabulky v programu)
+// Pokud si v programu definujete stejnou funkci, použije se ta vaše.
+size_t htab_hash_function(htab_key_t str);
+
+// Funkce pro práci s tabulkou:
+htab_t *htab_init(const size_t n);              // konstruktor tabulky
+size_t htab_size(const htab_t * t);             // počet záznamů v tabulce
+size_t htab_bucket_count(const htab_t * t);     // velikost pole
+
+htab_pair_t * htab_find(const htab_t * t, htab_key_t key);  // hledání
+htab_pair_t * htab_lookup_add(htab_t * t, htab_key_t key);
+
+bool htab_erase(htab_t * t, htab_key_t key);    // ruší zadaný záznam
+
+// for_each: projde všechny záznamy a zavolá na ně funkci f
+// Pozor: f nesmí měnit klíč .key ani přidávat/rušit položky
+void htab_for_each(const htab_t * t, void (*f)(htab_pair_t *data));
+
+void htab_clear(htab_t * t);    // ruší všechny záznamy
+void htab_free(htab_t * t);     // destruktor tabulky
+
+// výpočet a tisk statistik délky seznamů (min,max,avg) do stderr:
+void htab_statistics(const htab_t * t);
+
+#endif // HTAB_H__
diff --git a/src/tail.c b/src/tail.c
new file mode 100644
index 0000000..0d83119
--- /dev/null
+++ b/src/tail.c
@@ -0,0 +1,217 @@
+// main.c
+// Řešení IJC-DU2, příklad 1), 18.4.2023
+// Autor: Matyáš Oujezdský, FIT
+// Přeloženo: clang version 10.0.0-4ubuntu1
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+#include <limits.h>
+
+#define MAX_LINE_SIZE 4095
+
+typedef struct cb {
+    char **data;  // array of lines
+    size_t size;  // size of the buffer
+    size_t count; // current number of lines in buffer
+    size_t start; // index of first line
+    size_t end;   // index of last line
+} cb_t;
+
+// allocate neccesary memory and return pointer to circular buffer
+cb_t *cb_create(size_t n) {
+    cb_t *buffer = malloc(sizeof(cb_t));
+    if (!buffer) {
+        fputs("couldn't allocate memory for buffer\n", stderr);
+        return NULL;
+    }
+
+    buffer->data = calloc(n, sizeof(char *));
+    if (!buffer->data) {
+        fputs("couldn't allocate memory for lines in buffer\n", stderr);
+        free(buffer);
+        return NULL;
+    }
+
+    buffer->size = n;
+    buffer->count = 0;
+    buffer->start = 0;
+    buffer->end = 0;
+
+    return buffer;
+}
+
+/*
+input line to circular buffer at write pointer
+and increase write pointer
+*/
+char *cb_put(cb_t *cb, char *line) {
+    char *old_string = cb->data[cb->end];
+
+    cb->data[cb->end++] = line;
+    cb->end %= cb->size;
+    if (cb->count < cb->size) {
+        cb->count++;
+    }
+    if (old_string) {
+        cb->start++;
+        cb->start %= cb->size;
+    }
+    return old_string;
+}
+
+/*
+return string at the read pointer of circural buffer
+and increase read pointer
+*/
+char *cb_get(cb_t *cb) {
+    if (cb->count == 0) {
+        fputs("buffer is empty\n", stderr);
+        return NULL;
+    }
+    char *curr_line = cb->data[cb->start++];
+    cb->start %= cb->size;
+    cb->count--;
+    return curr_line;
+}
+
+// free every allocated part of circular buffer
+void cb_free(cb_t *cb) {
+    for (size_t i = 0; i < cb->size; ++i) {
+        if (cb->data[i]) {
+            free(cb->data[i]);
+        }
+    }
+    free(cb->data);
+    free(cb);
+}
+
+// reads file by character and at each \n sends the line to cb_put
+void read_file(cb_t *cb, FILE *stream) {
+    char tmp_char;
+    char *tmp_string = malloc(MAX_LINE_SIZE);
+    if (!tmp_string) {
+        fputs("couldn't allocate memory for tmp_string", stderr);
+        return;
+    }
+
+    bool exceeded = false;
+    bool discard_rest = false;
+
+    int i = 0;
+    while ((tmp_char = fgetc(stream)) != EOF) {
+        if (i + 1 >= MAX_LINE_SIZE) {
+            if (!exceeded) {
+                fputs("exceeded max line length\n", stderr);
+                exceeded = true;
+            }
+
+            discard_rest = true;
+        }
+
+        if (!discard_rest) {
+            tmp_string[i] = tmp_char;
+        }
+
+        // at \n end the string by '\0' and send the string to cb_put
+        if (tmp_char == '\n') {
+            tmp_string[i] = 0;
+            tmp_string = cb_put(cb, tmp_string);
+            if (!tmp_string) {
+                tmp_string = malloc(MAX_LINE_SIZE);
+            }
+            i = 0;
+        }
+
+        else if (!discard_rest) {
+            ++i;
+        }
+    }
+
+    if (tmp_string) {
+        free(tmp_string);
+    }
+}
+
+// print help (kind of self-explainatory)
+void print_help(char *file_name) {
+    printf("Usage: %s [OPTION] [FILE]\n", file_name);
+    printf("Print the last 10 lines of each FILE to standard output.\n\n\
+With no FILE, read standard input.\n\n\
+Mandatory arguments to long options are mandatory for short options too.\n\n\
+OPTION%30sFUNCTION\n",
+           "");
+    printf("-n, --number NUM%20soutput the last NUM lines (NUM must be > 1),\n\
+%38sinstead of the last 10\n\n",
+           "", "");
+    printf("-h, --help%26soutput the last NUM lines (NUM must be > 1),\n\
+%38sinstead of the last 10\n",
+           "", "");
+}
+
+int main(int argc, char **argv) {
+
+    size_t size = 10;
+    FILE *stream = stdin;
+
+
+    // make sure to read only first instance of -n or file names
+    bool file_read = false;
+    bool num_read = false;
+
+    for (int i = 1; i < argc; i++) {
+        // a argument -h or --help was passed, so print help
+        if (strcmp(argv[i], "-h") == 0 || strcmp(argv[i], "--help") == 0) {
+            print_help(argv[0]);
+            return 0;
+        }
+
+        // a argument -n or --number was passed,
+        // so chech next argument for number
+        if ((strcmp(argv[i], "-n") == 0 ||
+             strcmp(argv[i], "--number") == 0) && !num_read) {
+
+            num_read = true;
+
+            // check if there is a next argument and read it
+            if (argc > i + 1) {
+                size = atoi(argv[i + 1]);
+
+                // this happens with numbers too big or negative
+                if (size > LONG_MAX) {
+                    print_help(argv[0]);
+                    return 1;
+                }
+            }
+
+            // if the number is zero or not inputed
+            if (size == 0 || argc <= i + 1) {
+                print_help(argv[0]);
+                return 1;
+            }
+
+            // skip the number in the next loop cycle
+            i++;
+        }
+
+        // open the file and set it to be read from
+        else if (!file_read) {
+            file_read = true;
+            stream = fopen(argv[i], "r");
+            if (!stream) {
+                fprintf(stderr, "Counldn't open a file with name %s\n", argv[i]);
+                return 1;
+            }
+        }
+    }
+
+    cb_t *cb = cb_create(size);
+    if (!cb || !cb->data) {
+        return 1;
+    }
+    read_file(cb, stream);
+    while (cb->count) {
+        printf("%s\n", cb_get(cb));
+    }
+    cb_free(cb);
+}
diff --git a/src/wordcount.c b/src/wordcount.c
new file mode 100644
index 0000000..e69de29