diff --git a/exercism/acronym/acronym.c b/exercism/acronym/acronym.c
new file mode 100644
index 00000000..828b925c
--- /dev/null
+++ b/exercism/acronym/acronym.c
@@ -0,0 +1,87 @@
+#include <string.h>
+#include <stdio.h>
+#include <ctype.h>
+
+char *abbreviate(const char *phrase)
+{
+    char str[80];
+    strcpy(str, phrase);
+    char *p_str = str;
+    static char acr[80];
+    strcpy(acr, "");
+
+    /* for counting the words */
+    int counter = 0;
+
+    /* for position the words */
+    int index = 0;
+
+    /* for -loop variable */
+    int i = 0;
+
+    /* 
+        counts the empty-characters. 
+        for determine the number of words
+    */
+    while (p_str && (i < 80))
+    {
+        if (*p_str == ' ')
+        {
+            counter++;
+        }
+        if (i < 80)
+        {
+            p_str++;
+            i++;
+        }
+    }
+
+    i = 0;
+    counter++;
+    char words[counter][80];
+
+    /* initalizes words-array with empty strings */
+    for (i = 0; i < counter; i++)
+    {
+        strcpy(words[i],"");
+    }
+
+    /* rewind string */
+    p_str = str;
+
+    char *p_start = p_str;
+
+    /* collects each word in array 'words' */
+    while (p_str && (i <= 80))
+    {
+        if (*p_str == ' ')
+        {
+            *p_str = '\0';
+            strncat(words[index], p_start, 80);
+            index++;
+            p_start = p_str + 1;
+        }
+
+        if (i <= 80)
+        {
+            p_str++;
+            i++;
+        }
+    }
+
+    /* adds the last word */
+    *p_str = '\0';
+    strncat(words[index], p_start, 80);
+    index++;
+
+    /* builds the actual acronym */
+    for (i = 0; i < index; i++)
+    {
+        /* capitalize the first character */
+        words[i][0] = toupper(words[i][0]);
+        words[i][1] = '\0';
+        strcat(acr, words[i]);
+    }
+
+    return acr;
+}
\ No newline at end of file
diff --git a/exercism/acronym/acronym.h b/exercism/acronym/acronym.h
new file mode 100644
index 00000000..02eaeea2
--- /dev/null
+++ b/exercism/acronym/acronym.h
@@ -0,0 +1,6 @@
+#ifndef ACRONYM_H
+#define ACRONYM_H
+
+char *abbreviate(const char *phrase);
+
+#endif
diff --git a/exercism/hello-world/hello_world.c b/exercism/hello-world/hello_world.c
new file mode 100644
index 00000000..bd922123
--- /dev/null
+++ b/exercism/hello-world/hello_world.c
@@ -0,0 +1,7 @@
+#include "hello_world.h"
+
+const char *hello(void)
+{
+    /* string is pointer of the first character */
+    return  "Hello, World!";
+}
diff --git a/exercism/hello-world/hello_world.h b/exercism/hello-world/hello_world.h
new file mode 100644
index 00000000..e553b802
--- /dev/null
+++ b/exercism/hello-world/hello_world.h
@@ -0,0 +1,6 @@
+#ifndef HELLO_WORLD_H
+#define HELLO_WORLD_H
+
+const char *hello(void);
+
+#endif
diff --git a/exercism/isogram/isogram.c b/exercism/isogram/isogram.c
new file mode 100644
index 00000000..a54e3c81
--- /dev/null
+++ b/exercism/isogram/isogram.c
@@ -0,0 +1,46 @@
+#include <stdbool.h>
+#include <string.h>
+
+/*
+    is_isogram: returns true if the given string a isogram, otherwise false.
+*/
+bool is_isogram(const char phrase[]) 
+{
+
+    /* use 'unsigned' because of the function strlen(...) */
+    unsigned int i = 0;
+    unsigned int j = 0;
+
+    /* the current read character in the first for-loop */
+    char current_char = ' ';
+
+    /* return status */
+    bool status = true;
+
+    /* contains the length of the given string */
+    unsigned int len_phrase = strlen(phrase);
+
+    for (i = 0; i < len_phrase; i++ ) 
+    {
+        current_char = phrase[i];
+
+        /* makes sure the current character has no repetition */
+        for (j = i+1; j < len_phrase; j++)
+        {
+            if (current_char == phrase[j])
+            {
+                status = false;
+
+                /* 
+                    because the given string is none isogram.
+                    that means we can exit the nested for-loop.
+                */
+                goto end;
+            }
+        }
+    }
+
+    /* exit label */
+    end:
+        return status;
+}
\ No newline at end of file
diff --git a/exercism/isogram/isogram.h b/exercism/isogram/isogram.h
new file mode 100644
index 00000000..ae28cfa6
--- /dev/null
+++ b/exercism/isogram/isogram.h
@@ -0,0 +1,8 @@
+#ifndef ISOGRAM_H
+#define ISOGRAM_H
+
+#include <stdbool.h>
+
+bool is_isogram(const char phrase[]);
+
+#endif