The code as it is ( be it C, Pascal...) means nothing to the processor, but when you compile your code, the compiler translates that into a sequence of basic machine instructions, such as those you mentioned, and when you run it those instructions get loaded into memory and executed. This special file with instruction is no different than any other file, its just a sequence of data with a beggining and an end, it's up to the OS to determinate what can be executed.
As for input, when you type in your keyboard those keypreses ( which have known maped values) are pushed into a input buffer, that is periodically read.
If you type in "vead" on a text editor, the OS will create a stream that the program can read and copy those letters (that the computer usually sees as sequence of 8 bits) into it's own internal memory, and when you save it those will be copied to a non volatile memory and somewere on your HD we will have the sequence 01010110011001010110000101100100 (vead). Not a big mystery.