The set of fundamental operations that a computer is engineered to perform are known as it's instruction set. The fundamental operations of a computer tend to be very primitive operations; that is, each operation does very little, and it takes a lot of operations to accomplish significant work. But these fundamental operations can be done very quickly.

This small sample computes the sum of the integers from 1 to 1000

        mov      #0,sum     ; set sum to 0
        mov      #1,num     ; set num to 1
loop:   add      num,sum    ; add num to sum
        add      #1,num     ; add 1 to num
        cmp      num,#1000  ; compare num to 1000
        ble      loop       ; if num <= 1000, go back to 'loop'
        halt                ; end of program. stop running