How to use only tab (not space) in vim

Question

I prefer to use tab than white space(may be a little different from most of others)

But I found, when I hit Enter at the end of line, it will add some white spaces, but not tab. So, I have to delete them and press tab.

I want to know how to set vim as:

1. use only tab to indent the lines
2. a tab looks like 4-spaces, but actually is a tab
3. when hit enter at the end of a line, the new line is started with only tabs

I've googled for this for a while, but not found a good answer. Thank you in advance

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UPDATE

The answer @Alok has provided works well in most of cases. But I just found, sometimes, it depends on the file type. For example, if you are editing a haml file, and there is a haml.vim in your vimfiles/indent/, then all the tabs will be converted to space. So if you want it to be tab only, you should modify(or delete) the corresponding indent file.

Answer 1

The settings you are looking for are:

set autoindent
set noexpandtab
set tabstop=4
set shiftwidth=4

As single line:

set autoindent noexpandtab tabstop=4 shiftwidth=4

autoindent can be replaced with smartindent or cindent, depending upon your tastes. Also look at filetype plugin indent on.

http://vim.wikia.com/wiki/Indenting_source_code