diff --git a/ANSWERS.md b/ANSWERS.md
index 9e5261a..058fe87 100644
--- a/ANSWERS.md
+++ b/ANSWERS.md
@@ -19,7 +19,7 @@ Please use [markdown](https://help.github.com/articles/markdown-basics) formatin
 
 Make another directory inside the `unixstuff` directory called `backups`
 
-**Answer:** *YOUR ANSWER HERE*
+**Answer:** *mkdir unixstuff, mkdir backups*
 
 ###Exercise 1b
 
@@ -27,31 +27,31 @@ Use the commands `cd`, `ls` and `pwd` to explore the file system.
 
 (Remember, if you get lost, type `cd` by itself to return to your home-directory)
 
-**Answer:** *YOUR ANSWER HERE*
+**Answer:** *pwd == print working directory. cd == change directory. ls == list*
 
 ###Exercise 2a
 
 Create a backup of your `science.txt` file by copying it to a file called `science.bak`
 
-**Answer:** *YOUR ANSWER HERE*
+**Answer:** *cp science.txt science.bak, mv science.bak unixstuff/backups/*
 
 ###Exercise 2b
 
 Create a directory called `tempstuff` using `mkdir`, then remove it using the `rmdir` command.
 
-**Answer:** *YOUR ANSWER HERE*
+**Answer:** *mkdir tempstuff, rmdir tempstuff*
 
 ###Exercise 3a
 
 Using the above method, create another file called `list2` containing the following fruit: orange, plum, mango, grapefruit. Read the contents of `list2`.
 
-**Answer:** *YOUR ANSWER HERE*
+**Answer:** *cat > list2*
 
 ###Exercise 3b
 
 Using pipes, display all lines of `list1` and `list2` containing the letter 'p', and sort the result.
 
-**Answer:** *YOUR ANSWER HERE*
+**Answer:** *cat list1 list2 | grep p | sort*
 
 ###Exercise 5a
 
@@ -59,88 +59,104 @@ Try changing access permissions on the file `science.txt` and on the directory `
 
 Use `ls -l` to check that the permissions have changed.
 
-**Answer:** *YOUR ANSWER HERE*
+**Answer:** *chmod a+rw science.txt, chmod go-rx backups*
 
 ##Shell questions
 
 1. What option with the command `rm` is required to remove a directory?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *rmdir*
 1. What is the command used to display the manual pages for any command?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *man command*
 1. What command will show the first 5 lines of an input file?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *head -5 filename*
 1. What command can be used to rename a file?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *mv filename newfilename*
 1. What option can we given to `ls` to show the hidden files?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *ls -a (-a for all files)*
 1. What will the command `cat -n file` do?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *output lines with the line numbers.*
 1. What will the command `echo -n hello` do?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *display a line of text without a new line.*
 1. What command will display s list of the users who currently logged in in the system?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *who*
 1. How do you change password on your account?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *passwd*
 1. How can you list a file in reverse order?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *tac ‘list’*
 1. What does the `less` command do?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *You can view the file(no need to load the entire file at once)with backward and forward moving possible.*
 1. With `less` how do you navigate?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *enter for next line, space for new page, q for quit*
 1. What command will display the running processes of the current user?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *ps*
 1. What command can be used to find the process(es) consuming the most CPU?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *ps -aux | head -5*
 
 ##vi questions
 1. How do we save a file in `vi` and continue working?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *:w filename*
 1. What command/key is used to start entering text?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *i key*
 1. What are the different modes the editor can be in?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *COMMAND and INSERT*
 1. What command can be used to place the cursor at the beginning of line 4?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *:4*
 1. What will `dd` command do (in command-mode)?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *dd deletes the whole line the cursor is on*
 1. How do you undo the most recent changes?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *u*
 1. How do you move back one word?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *b*
 
 ##The C Language and Make tool Questions
 
 1. How do you use `gcc` to only produce the `.o` file?  What is the difference between generating only the `.o` file, and building the `hello` executable done in the previous compilation above?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *gcc hello.c -c( -o hello.o), the first method doesn't link to system libraries.*
 1. Give the command for compiling with `debug` enabled instead of normal compilation for the two examples shown in Listing 2 and Listing 3. Explain how to turn debugging on/off for the two cases.
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *gcc <file.c> -d DEBUG. The selectable (listing 3) must be turned on in the source code. *
 1. Give a brief pros and cons discussion for the two methods to add debug code shown in Listing 2 and Listing 3.
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *Listing 2 will only compile the required debug code if the user has defined it while compiling. Listing 3 will have uneccessary code if it isn't used for debugging.*
 1. Provide the command for generating the *map* file. Which of the `gcc` tools is responsible for producing a *map* file?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *gcc hello.c -WL,-Map=hello.map hello.c. The linker produces the *map* file.*
 1. What is the content of each of the sections in a *map* file. Explain briefly.
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *.test contains the machine instructions for the program. .bss contains variables that is not initialized or is intilized as being null.
+  .data contains static read/write data that the codes create.
+  .rodata contains constant read only data. *
 1. Rewrite `hello.c` to produce entries in the *map* file for `.data`, `.bss`, and `.rodata`. Hint: This can be done by adding one variable for each type to the file.
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *int data = 30, int bss, static const int fin = 300*
 1. Add the following function to `hello.c`: `double multiply(double x1, double x2)`, which returns `x1*x2`. Use `gcc` to generate an assembly code listing for the program, and examine the assembly code. What assembly instructions are used to do this? Repeat this task, but now replace `double` with `float`. Explain!
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *gcc -c -g -Wa,-a,-ad [other GCC options] foo.c > foo.lst (foo.lst C/assembly listing),With double the assembly instructions are: movsd/mulsd. With float the assembly instructions are: movss/mulss.*
 1. How does `make` know if a file must be recompiled?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *Using the timestamp of the source files.*
 1. Provide a `make` command to use a file named `mymakefile` instead of the default `makefile`.
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *make -f mymakefile*
 1. How do you implement an *include guard*, and why is it needed?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *insert #ifndef … #define … #endif /* … */. It guards from compilation errors if a type is define twice.*
 
 ##Library Task
 
 Insert your code between the brackets `{}`:
 
-    void main( int argc, char *argv[] )
-	{
+    void main( int argc, char *argv[] ){
+            int i;
+            double tab[TAB_SIZE] = {4.3, 2.3, 6.4, 1.2, 1.3};
+            double sum;
+
+            sum = tab_sort_sum( tab, TAB_SIZE );
+
+            printf("sum=%f\n", sum);
+            for ( i=0; i<TAB_SIZE;i++)
+                    printf("tab[%d]=%f\n", i, tab[i]);
     }
-    
-	double tab_sort_sum( double *tab, int tab_size )
-	{
-	}
+
+    double tab_sort_sum ( double* tab, int TAB_SIZE ) {
+            int i;
+            double sum=0;
+            qsort (tab, TAB_SIZE, sizeof(double), dblClmp);
+            for(i=0;i<tab_size;i++)
+                    sum = sum + tab[i];
+            return sum;
+    }
+