Frode vdm

ANSWERS.md

@@ -19,33 +19,38 @@ 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\backups*
 
 ###Exercise 1b
 
 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:** *cd unixstuff*
 
 ###Exercise 2a
 
 Create a backup of your `science.txt` file by copying it to a file called `science.bak`
 
-**Answer:** *YOUR ANSWER HERE*
+**Answer:** *cat science.txt>science.bak*
 
 ###Exercise 2b
 
 Create a directory called `tempstuff` using `mkdir`, then remove it using the `rmdir` command.
 
-**Answer:** *YOUR ANSWER HERE*
+**Answer:** *mkdir tempstuff
+rmdir -r 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:** *"orange">list2
+"plum">>list2
+"mango">>list2
+"grapefruit">>list2
+cat list2*
 
 ###Exercise 3b
 
@@ -64,83 +69,103 @@ Use `ls -l` to check that the permissions have changed.
 ##Shell questions
 
 1. What option with the command `rm` is required to remove a directory?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *rm -r dirname removes directories.*
 1. What is the command used to display the manual pages for any command?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *man commandname brings up the manual for a command.*
 1. What command will show the first 5 lines of an input file?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *head -5 filename displays the first 5 lines of a file.*
 1. What command can be used to rename a file?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *mv filename newfname renames a file.*
 1. What option can we given to `ls` to show the hidden files?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *ls -a shows the hidden files together with everything else.*
 1. What will the command `cat -n file` do?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *cat -n filename prints the file, with linenumbers.*
 1. What will the command `echo -n hello` do?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *echo -n "hello" will print "hello" to standard output, with no 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 displays all online users.*
 1. How do you change password on your account?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *passwd is used to change the password.*
 1. How can you list a file in reverse order?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *cat -n filename>tmp.txt
+sort -rn tmp.txt
+rm tmp.txt*
 1. What does the `less` command do?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *less searches for a pattern in a file.*
 1. With `less` how do you navigate?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *you use /searchword to search and n to go to the next hit.*
 1. What command will display the running processes of the current user?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *ps displays your processes.*
 1. What command can be used to find the process(es) consuming the most CPU?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *top displays the processes using most CPU.*
 
 ##vi questions
 1. How do we save a file in `vi` and continue working?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *esc:w [filename] saves the file without quitting.*
 1. What command/key is used to start entering text?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *the i key can be used to enter text.*
 1. What are the different modes the editor can be in?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *command mode and insert mode.*
 1. What command can be used to place the cursor at the beginning of line 4?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *:4 will take the cursor to line 4*
 1. What will `dd` command do (in command-mode)?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *dd will erease the curent line.*
 1. How do you undo the most recent changes?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *u or :u undo the most recent changes*
 1. How do you move back one word?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *b moves back one word.*
 
 ##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 -c hello.c will generate compiled but unlinked object files from the sources, whereas a full compile will link everything together in an excecutable file.*
 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 -g hello.c compiles with debug mode enabled in the compiler. For the two programs, however, Listing 2 needs to have the DEBUG tag defined, while Listing 3 needs to have the debug variable set to something else than zero.*
 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:** *For Listing 2, debug code is left out already during compilation and will not be present unless compiled with debug enabled. For Listing 3, debug code will be included in the program code after compilation, but it will not be excecuted unless the flag is specified. The method of Listing 2 is great for saving space, but the method of Listing 3 allows for code that's easier to read along with more flexible debug intergration.*
 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 -o hello -Wl,-Map=hello.map hello.c, the linker makes this file.*
 1. What is the content of each of the sections in a *map* file. Explain briefly.
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *The map file defines where libraries, variables and code will be allocated in memory. You have the stack for stack based functions, dataareas for constants and variables, and code area for code.*
 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:** *tried adding variables, but program wouldn't recognize the globally defined string*
 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:** *The x86 instruction set has instructions for integer multiplication, but not for floating point multiplication (unless a numeric x87 coproccessor is used. Since the 486DX these coprocessors have been intergrated in the main CPU)*
 1. How does `make` know if a file must be recompiled?
-  - **Answer:** *YOUR ANSWER HERE*
+  - **Answer:** *it's predefined. Libraries does not need to be recompiled.*
 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:** *To prevent several inclusions of a library. This saves space and prevents linking conflicts.*
 
 ##Library Task
 
 Insert your code between the brackets `{}`:
 
-    void main( int argc, char *argv[] )
+	void main( int argc, char *argv[] )
 	{
-    }
+		argv = char[argc];
+		for(int i=0; i<argc; i++)
+        	{
+			argv[i] = rand(MIN, MAX);
+        	}
+		double sum = tab_sort_sum(argv, argc);
+		for(int i=0; i<argc; i++)
+        	{
+			printf(argv[i],"\n");
+		}
+		printf(sum,"\n");
+	}
 
 	double tab_sort_sum( double *tab, int tab_size )
 	{
+		tab = qsort(tab);
+		double sum = 0;
+		for(int i=0; i<tab_size; i++)
+		{
+			sum = sum + tab[i];
+		}
+		return sum;
 	}
 
 

mysrc.c

@@ -0,0 +1,16 @@
+#include <stdio.h>
+
+char[] alph = "Hello, world!\n\0";
+
+int main(void)
+{
+        double a = 5;
+        double b = 7;
+        double c = a*b;
+        float a2 = 5.0;
+        float b2 = 7.0;
+        float c2 = a2*b2;
+        int n = 0;
+        printf(alph);
+        return n;
+}