C Language
C is one of the most widely used programming languages of all time and there are very few computer architectures for which a C compiler does not exist. C has greatly influenced many other popular programming languages, most notably C++, which began as an extension to C.
The best way to learn a new ``human'' language is to speak it right from the outset, listening and repeating, leaving the intricacies of the grammar for later. The same applies to computer languages--to learn C, we must start writing C programs as quickly as possible.
There are plenty of books, tutorials, courses about C language. These are two good references: