Is it right to write multiple and separate <script > on a page?

Question

While writing JavaScript code, I Separate each code block with <script> tags

<script type="text/javascript">
 //---- code block 1--------- 
</script>   

<script type="text/javascript">
    ----code block 2-----
</script>

<script type="text/javascript">
$(document).ready.(function(){
 // code block3
});
</script>

I want to know that is it good practice to write separate <script type="text/javascript"></script> on the same page

--or--

We have to write all JavaScript code under one <script>

What are the technical differences in each way?