1. Computer Programming Methodology Instructions thru hardware
COS 130
Computer Programming Methodology
Instructions thru hardware

2. Sign in sheet

3. Algorithm Like a Recipe, but . . . Strictly defines the order of steps
“In mathematics and computing, an algorithm is a procedure (a finite set of well-defined instructions) for accomplishing some task which, given an initial state, will terminate in a defined end-state.” - Wikipedia
Like a Recipe, but . . .
Strictly defines the order of steps

4. Program “A computer program is a list of instructions
to be executed by the computer.”
- Wikipedia
Programs implement algorithms
Programs are executable by “machines”
Programs group instructions into a unit of work

5. Instructions
Noun and a Verb
Examples:
Kick ball
Print “Hello World”

6. Problem Solving Decomposition How do you eat an elephant?
One bite at a time!
Break big problems into little problems

7. Problem Solving with Instructions
Based on Verbs?
Based on Nouns?
Example:
Make a pie

8. Verbs Make Apple pie prep assemble cook Wash apples Slice apples
Combine dry
ingredients
Coat apples
With brown sugar
Place pie
In oven
Pre-heat
oven

9. Nouns Apple Pie Crust Filling Flour Apples Eggs Brown Sugar Sugar
Cinnamon

10. Verbs vs. Nouns Verbs Solve Top Down Nouns Solve Bottom Up Plato
Aristotle
Structured
Programming
Object Oriented
Programming

11. However, eventually we revert to verbs
More about Nouns
Already in the problem domain waiting to be discovered
Concrete – see, hear, touch, taste them
More permanent
Class registration example
However, eventually we revert to verbs

12. What Makes Computers Different?

13. When implemented on a computer
Noun
Data
Verb
Instruction

14. Flexible Data Representation
Herman Hollerith and the
1890 census
IBM Archives -

15. Flexible Instruction Representation
Wikipedia -
Wikipedia -
Jacquard loom

16. Combine Flexible Data with Flexible Instructions
Data is represented as 1’s and 0’s
Instructions are represented as 1’s and 0’s
Therefore we can write programs that manipulate programs as their data
Examples:
Compilers
Operating Systems
This should make your head hurt!

17. National Science Museum of the UK
Data and Instructions
National Science Museum of the UK
Babbage’s Engines – 1830’s

18. A Brief Introduction to Computer Hardware

19. Top Level Hardware CPU I/O Devices Memory Storage High Speed
The “Brain”
Performs Arithmetic
Controls Execution
CPU
I/O
Devices
Memory
Storage
High Speed
Long term storage
Access to the outside

20. Wikipedia - http://en.wikipedia.org/wiki/Central_processing_unit
CPU Details
Program
Counter
Arithmetic
Logic Unit
Wikipedia -

21. Memory Details . . . . . . A sequence of storage locations
1024
1025
1026
1027
1028
1029
1030
1031
A sequence of storage locations
Much like mailboxes
Each box has an address
Each box can hold 32 bits
Each box can be randomly accessed
Goes away when the power is turned off

22. I/O Details Slower than memory Varies depending on the device
Accessed differently then memory usually read / write
Disks are special they are often used as faux memory

23. Hardware Philosophy Simple – add, compare, move
Speed more important than sophistication
Lots of simple steps fast to get results
Keep the CPU busy
Driven by a “clock”, everything must happen on the beat

24. Assignment Operator = maxStudents = 30; Left side must be a variable
The value from the right is put in the spot in memory named on the left
. . . 30
maxStudents

25. maxStudents – curEnroll
Example
seatsLeft =
maxStudents – curEnroll ;
. . . 33
curEnroll
. . . -3 -3
seatsLeft
. . . 30
maxStudents

26. Wikipedia - http://en.wikipedia.org/wiki/Central_processing_unit
Example in the CPU
Fetch Instruction
MV Mem R3
MV Mem R7
Add R3, R7, R2
MV R2 Mem
Program
Counter
Arithmetic
Logic Unit
Wikipedia -