Update ex1-reading-fasta/description

ex1-reading-fasta/description

@@ -20,7 +20,7 @@ The FASTA format has to separate parts:
 2. sequence
 
 
-Thus, the excercise for reading FASTA file briefly looks like this:
+Thus, the excercise for reading FASTA file, in C, briefly looks like this:
 
 1. Select sequence and save it to a file, e.g. seq.fasta
 
@@ -28,4 +28,20 @@ Thus, the excercise for reading FASTA file briefly looks like this:
 
 https://cplusplus.com/reference/cstdio/fopen/
 
-Tip: Use correct mode.
+Tip: Use correct mode.
+
+3. Read the file, line by line, using e.g. snippet of code from here:
+
+https://cplusplus.com/forum/beginner/22558/
+
+4. Check if the lines starts with ';' or with '>', then skip such a line
+
+If the line is OK, then count how many A, C, T, G are in the given line and 
+save that information.
+
+In order to check if the line starts with a given character you can 
+simply use index of a string (line[0] - this is first character in the 
+array line).
+
+The end.
+