diff --git a/content/cyb/basic/index.md b/content/cyb/basic/index.md
index ffee3b8..b92f52b 100644
--- a/content/cyb/basic/index.md
+++ b/content/cyb/basic/index.md
@@ -9,6 +9,10 @@ description: "Subjects about C language"
 This category shows training exercises about C language. For all questions,
 please ask on the BackToBasics' [Discord server](https://discord.gg/SJGWzkU2gd).
 
+We cannot use the intranet, so there are somes given files. Please play the
+game and do not read the test file. You can download it
+[here](https://github.com/BackToBasicsEpita/CyberRef).
+
 A Makefile is already given with these rules:
 
 - `basics`: compiles ;
@@ -16,29 +20,6 @@ A Makefile is already given with these rules:
 - `check`: runs the testsuite ;
 - `clean`: removes all trash files.
 
-Moreover, you must use the following header file `basics.h`:
-
-```c
-#ifndef BASICS_H
-#define BASICS_H
-
-#include <stdlib.h>
-
-struct pair
-{
-    int x;
-    int y;
-};
-
-void fizzbuzz(int n);
-size_t my_strlen(char *s);
-long binary_number(char str[]);
-int hamming_distance(char *dna1, char *dna2);
-int is_isogram(char *s);
-struct pair move_robot(struct pair current, char *directions);
-
-#endif /* !BASICS_H */
-```
 
 You are only allowed to uses the functions defined in the following headers:
 - stdio.h
@@ -88,7 +69,7 @@ size_t my_strlen(char *s);
 ```
 
 This functions returns the length of the string argument. The string can be
-null.
+null, and its size will be 0.
 
 # Binary number
 
@@ -99,8 +80,72 @@ long binary_number(char str[]);
 ```
 
 This function returns the integer in decimal corresponding to the binary number
-given in argument.
+given in argument. If a caracter does not correspond to a binary digit, return
+-1.
+
+## Example
+
+The output of `binary_number("110")` is `6`.
+
+The output of `binary_number("This is not correct")` is `-1`.
+
+# Hamming Distance DNA
+
+You have to implement the following function:
+
+```c
+int hamming_distance(char *dna1, char *dna2);
+```
+
+This function returns the number of differents characters between the two
+strings given in arguments.
+
+We read DNA using the letters C,A,G and T. If there is another caracter than
+the previous one, return -1. Moreover, if the size of the two parameters are
+not equal, return -1.
+
+## Example
+
+The output of `hamming_distance("CAGT", "GAGT")` is `1`.
+
+# Isogram
+
+You have to implement the follwing function:
+
+```c
+int is_isogram(char *s);
+```
+
+This function returns if the given string is an isogram. An isogram word or
+sentence is a word or a phrase without a repetiting letter, however spaces and
+non letter caracters are allowed to appear multiple times.
+
+## Example
+
+`House` is an isogram word, but `Test.` is not.
+
+# Move Robot
+
+You have to implement the following function:
+
+```c
+struct pair move_robot(struct pair current, char *directions);
+```
+
+Moreover, you have to implement the `pair` structure with two integer: `x` and
+`y`.
+
+This function moves a robot in the current coordinates on a grid from a string
+of directions and returns the new coordinates of the robot.
+
+The string of directions corresponds to a string of operations done on the
+robot:
+
+- `U` for up ;
+- `L` for left ;
+- `D` for down ;
+- `R` for right.
 
 ## Example
 
-The output of `my_strlen("110")` is `6`.
+The output of `move_robot({1, 1}, "UL")` is the structure pair `{0, 2}`.