Firstly, I saw topics such as 'How to install manually a software...' but it did not solve my problem. I've downloaded Scilab 5.4.1 from the official website and I extracted the .tar.gz file into:

/home/scilab-5.4.1

I then tried the commands below, but they gave several errors:

$ cd scalib-5.4.1

$ configure        @1

$ make             @2

$ make install     @3

these gave the following messages in the terminal:

@1: configure: command not found

@2: make: *** No targets specified and no makefile found.  Stop.

@3: make: *** No rule to make target `install'.  Stop.

I tried following commands:

$ cd scilab-5.4.1

$ cd bin

$ scilab

which gave the message:

The program 'scilab' is currently not installed.  You can install it

by typing: sudo apt-get install scilab