Add some new program

[dilippuri]

I've have added some new program from chapter 4 those are: 4_25, 4_33, 4_37. pls merge this request I am going add all the remaining program which are yet to code later actually I am working on it. :+1:

[lbraglia]

hi, thank you.

I'm a little busy now. I'll give it a check asap