Computers

One of the most  important invention in the design of digital  circuits  is that  of the general- purpose "stored program" computer or device. Computers are a particular type of digital  circuits  that are used as general purpose:  the  same  actual  circuit  can operate any  transformation between its outputs and  its inputs. Which  particular transformation it operates is governed by a program, which  is some parts of physical switches, or information given on an external physical memory, such as tapes or a cards, or information saved in some sort of internal physical memory.

Exactly what  operations a computer can do relays on the amount of memory it has; and  also on the time  you  want to wait.  So, although a general-purpose computer may do anything a special-purpose digital electronics circuit may do, in the information processing sense, the computer can be slower  or use more power. However, operating  general-purpose computers can save  effort and time.  It is much  simpler and  easier  to debug and  change and manufacture software than  hardware.  The abstractions and modularity that  software PCAP systems provides us are even more powerful than  those given from the digital  circuit abstraction.

Again,  we may see how  abstraction divide use from  information;  we don't  require  to know  how  the circuits inside a computer machine are designed, we just have to know the methods by which we may use them and the constraints under which  they operate.