diff --git a/ch_03/exercise_03-05/compile.sh b/ch_03/exercise_03-05/compile.sh
index ac167b9..89ecad1 100755
--- a/ch_03/exercise_03-05/compile.sh
+++ b/ch_03/exercise_03-05/compile.sh
@@ -10,10 +10,10 @@ hex_octal_conv_lib_root_dir="../../libraries/hex_octal_conv"
 hex_octal_conv_lib_include_dir="$hex_octal_conv_lib_root_dir/include"
 hex_octal_conv_lib_dir="$hex_octal_conv_lib_root_dir/bin/static"
 
-gcc -c main.c -I"$hex_octal_conv_lib_include_dir" -o bin/main.o -O3
+gcc -c main.c -I"$hex_octal_conv_lib_include_dir" -std=gnu99 -o bin/main.o -O3
 
 cd $hex_octal_conv_lib_root_dir
 ./compile.sh "release"
 cd $current_dir
 
-gcc bin/main.o -L"$hex_octal_conv_lib_dir" -lhexoctalconv -o bin/a.out -O3
+gcc bin/main.o -L"$hex_octal_conv_lib_dir" -lhexoctalconv -std=gnu99 -o bin/a.out -O3
diff --git a/ch_03/exercise_03-05/main.c b/ch_03/exercise_03-05/main.c
index 54cd39a..0fceb64 100644
--- a/ch_03/exercise_03-05/main.c
+++ b/ch_03/exercise_03-05/main.c
@@ -1,6 +1,6 @@
 /*
  *
- * Exercise 3-5. Write a function itob(n,s,b that converts the integer
+ * Exercise 3-5. Write a function itob(n,s,b) that converts the integer
  * m into a base b character representation in the string s. In
  * particular, itob(n,s,16) formats s as a hexadecimal integer in s.
  *
@@ -9,19 +9,79 @@
  */
 
 #include <stdio.h>
+#include <stdlib.h>
 
 #include "hex.h"
 
+// Only bases of 8 and 16 are supported. So Hexidecimal or octal
+// Returns -1 if invalid. and 1 if valid
+int itob(int n, char *s, int b);
+
 void test();
 
+
 int main()
 {
-    test();
+    // test();
+    const int number = 128;
+    const int base_value = 8;
+    char value[1024];
+
+    int result = itob(number, value, base_value);
+
+    if (result == -1)
+    {
+        printf("Base %d is not supported\n", base_value);
+
+        return -1;
+    }
+
+    if (base_value == 8)
+    {
+        printf("%d is in octal (%d base) %s\n", number, base_value, value);
+    }
+    else if (base_value == 16)
+    {
+        printf("%d is in hexidecimal (%d base) %s\n", number, base_value, value);
+    }
 
     return 0;
 }
 
 
+int itob(int n, char *s, int b)
+{
+    int result = 0;
+
+    if (! (b == 8 || b == 16))
+    {
+        // Neither 8 or 16 based. Invalid
+        result = -1;
+
+        return result;
+    }
+
+    const int ARRAY_SIZE = 1024;
+
+    char number_value[ARRAY_SIZE];
+    HexOctalConv_itoa(n, number_value, 10);
+
+
+    // printf("Number %d is %s in string\n", n, number_value);
+
+    if (b == 8)
+    {
+        HexOctalConv_number_converted_to_octal(s, number_value);
+    }
+    else if (b == 16)
+    {
+        HexOctalConv_number_converted_to_hex(s, number_value);
+    }
+
+    return result;
+}
+
+
 void test()
 {
     char *number = "21";
diff --git a/libraries/hex_octal_conv/compile.sh b/libraries/hex_octal_conv/compile.sh
index 9eaef60..e9d8683 100755
--- a/libraries/hex_octal_conv/compile.sh
+++ b/libraries/hex_octal_conv/compile.sh
@@ -19,13 +19,13 @@ fi
 
 if [ "$compile_type" = "debug" ]; then
     echo "Compiling for debug version"
-    gcc -c src/hex.c -Iinclude -o bin/static/hex.o -O0
+    gcc -c src/hex.c -Iinclude -std=gnu99 -o bin/static/hex.o -O0
 elif [ "$compile_type" = "release" ]; then
     echo "Compiling for release version"
-    gcc -c src/hex.c -Iinclude -o bin/static/hex.o -O3
+    gcc -c src/hex.c -Iinclude -std=gnu99 -o bin/static/hex.o -O3
 else
     echo "Compiling for debug by default"
-    gcc -c src/hex.c -Iinclude -o bin/static/hex.o -O0
+    gcc -c src/hex.c -Iinclude -std=gnu99 -o bin/static/hex.o -O0
 fi
 
 ar rcs bin/static/libhexoctalconv.a bin/static/hex.o
diff --git a/libraries/hex_octal_conv/include/hex.h b/libraries/hex_octal_conv/include/hex.h
index 025cf30..cb63801 100644
--- a/libraries/hex_octal_conv/include/hex.h
+++ b/libraries/hex_octal_conv/include/hex.h
@@ -11,6 +11,7 @@ char HexOctalConv_convert_hex_part(int value);
 
 void HexOctalConv_number_converted_to_hex(char *hex_value, char *value);
 void HexOctalConv_number_converted_to_octal(char *octal_value, char *value);
+void HexOctalConv_itoa(int value, char *str, int base);
 
 
 static long rudy_pow(long value, int power);
diff --git a/libraries/hex_octal_conv/src/hex.c b/libraries/hex_octal_conv/src/hex.c
index e6b562a..30826d1 100644
--- a/libraries/hex_octal_conv/src/hex.c
+++ b/libraries/hex_octal_conv/src/hex.c
@@ -8,12 +8,12 @@ int HexOctalConv_hex_converted_to_number(char *value)
 {
     int number = 0;
     int power = 0;
-    int string_size = size_of_string(value);
+    const int string_size = size_of_string(value);
 
     for (int i = (string_size - 1); i >= 0; --i)
     {
-        char hex_part = value[i];
-        int number_part = HexOctalConv_hex_part_to_number(hex_part);
+        const char hex_part = value[i];
+        const int number_part = HexOctalConv_hex_part_to_number(hex_part);
         number += number_part * rudy_pow(16, power);
 
         ++power;
@@ -29,8 +29,8 @@ int HexOctalConv_octal_converted_to_number(char *value)
 
     for (int a = size_of_string(value) - 1; a >= 0; --a)
     {
-        int octal_part = value[a] - '0';
-        int octal_power = octal_part * rudy_pow(8, power_value++);
+        const int octal_part = value[a] - '0';
+        const int octal_power = octal_part * rudy_pow(8, power_value++);
         octal_converted_to_number += octal_power;
     }
 
@@ -107,9 +107,9 @@ char HexOctalConv_convert_hex_part(int value)
 
 void HexOctalConv_number_converted_to_hex(char *hex_value, char *value)
 {
-    printf("Starting process to convert %s to hexidecimal\n", value);
-    int number_value = atoi(value);
-    int string_size = size_of_string(value);
+    // printf("Starting process to convert %s to hexidecimal\n", value);
+    const int number_value = atoi(value);
+    const int string_size = size_of_string(value);
 
     int hex_start = 0;
 
@@ -118,11 +118,10 @@ void HexOctalConv_number_converted_to_hex(char *hex_value, char *value)
         const double quotient = number / 16.0;
         const int quotient_trunecated = number / 16;
         const double remaining = quotient - quotient_trunecated;
-        int number_hex_part = remaining * 16;
+        const int number_hex_part = remaining * 16;
 
-        char hex_part = HexOctalConv_convert_hex_part(number_hex_part);
+        const char hex_part = HexOctalConv_convert_hex_part(number_hex_part);
         hex_value[hex_start++] = hex_part;
-        // printf("%s\n", hex_value);
 
         if (number < 16)
         {
@@ -142,7 +141,7 @@ void HexOctalConv_number_converted_to_hex(char *hex_value, char *value)
 
 void HexOctalConv_number_converted_to_octal(char *octal_value, char *value)
 {
-    int value_number = atoi(value);
+    const int value_number = atoi(value);
     int index = 0;
 
     for (double quotient_number = value_number; (quotient_number >= 0);)
@@ -155,9 +154,9 @@ void HexOctalConv_number_converted_to_octal(char *octal_value, char *value)
         else
         {
             quotient_number /= 8;
-            int trunecated_quotient_number = quotient_number;
-            double remaining = quotient_number - trunecated_quotient_number;
-            int octal_part = remaining * 8;
+            const int trunecated_quotient_number = quotient_number;
+            const double remaining = quotient_number - trunecated_quotient_number;
+            const int octal_part = remaining * 8;
 
             octal_value[index] = octal_part + '0';
             quotient_number = trunecated_quotient_number;
@@ -170,12 +169,54 @@ void HexOctalConv_number_converted_to_octal(char *octal_value, char *value)
 
     for (int a = 0; a <= (index / 2); ++a)
     {
-        char tmp = octal_value[a];
+        const char tmp = octal_value[a];
         octal_value[a] = octal_value[(index - 1) - a];
         octal_value[(index - 1)] = tmp;
     }
 }
 
+void HexOctalConv_itoa(int value, char *str, int base)
+{
+   	static char num[] = "0123456789abcdefghijklmnopqrstuvwxyz";
+	
+	char *wstr = str;
+	
+	int sign;
+
+    div_t res;
+
+	// Validate base
+	if (base < 2 || base > 35)
+    {
+        *wstr='\0';
+        
+        return;
+    }
+	
+	// Take care of sign
+	if ((sign = value) < 0)
+    {
+        value = -value;
+    } 
+
+	// Conversion. Number is reversed.
+	do
+    {
+        res = div(value, base);
+
+        *wstr++ = num[res.rem];
+    } while(value = res.quot);
+	
+	if (sign < 0)
+    {
+        *wstr++= '-';
+    }
+	
+	*wstr='\0';
+	
+    reverse_order(str);
+}
+
 
 
 
@@ -212,15 +253,15 @@ static int size_of_string(char *value)
 
 static void reverse_order(char *value)
 {
-    int string_size = size_of_string(value);
+    const int string_size = size_of_string(value);
 
-    for (int i = 0;; ++i)
+    for (int i = 0; i <= ((string_size - 1) / 2); ++i)
     {
-        char tmp = value[string_size - i - 1];
+        const char tmp = value[string_size - i - 1];
         value[string_size - i  - 1] = value[i];
         value[i] = tmp;
 
-        int is_odd = string_size % 2;
+        const int is_odd = string_size % 2;
 
         if (is_odd == 1 && (string_size / 2) == ((i + 1)))
         {
diff --git a/libraries/test_library1/compile.sh b/libraries/test_library1/compile.sh
index ffaa7e7..d10c6f6 100755
--- a/libraries/test_library1/compile.sh
+++ b/libraries/test_library1/compile.sh
@@ -8,8 +8,9 @@ if [ ! -d "bin/static" ]; then
     echo "created bin/static directory"
 fi
 
-gcc -c src/test.c -Iinclude -o bin/static/test.o
+gcc -c src/test.c -Iinclude -o -std=gnu99 bin/static/test.o
 
+# For shared libraries.
 # gcc -fPIC src/test.c -Iinclude -o bin/shared/test.o
 
 ar rcs bin/static/libtestlibrary.a bin/static/test.o