lecture #2

qccs12.blogspot.com

blackboard

attendance

Incomplete policy is the same college-wide; you need to request

actual content

what is a computer?
something that computes

what does a "computer" need?
input
output
memory
control
mathematical ability

von Neumann architecture

from special purpose machine to
a universal computer
(general purpose computer)

hardware (physical machine)
software (instructions)

von Neumann architecture
conceptual model of computing

Finite State Automata
Turing Machines

Von Neumann architecture
http://en.wikipedia.org/wiki/Von_Neumann_architecture

look at the diagram there

CPU (central processing unit)
ALU (arithmetic / logic unit)
control unit

Memory (in this case, RAM)

examples of output:
printer
speaker
screen

examples of input:
mouse
keyboard
mike

Adding machine.
program:
1) say "please enter a number"
2) get the number, store it in X
3) say "please enter another number"
4) get the number, store it in Y
5) add X and Y, store it in Z
6) say X "+" Y "=" Z
7) Go to step 1

initially, this program will be stored in long-term memory. hard drive.

double-click, copies it to short-term memory. RAM.

RAM stores instructions and data

control unit has IP (instruction pointer)
IP: 1

data is carried via the "bus"

fetch-execute cycle

with that last step 7, we loop

register; really really short term memory, inside the CPU itself