Welcome Aboard – Chapter 1

1. Welcome Aboard – Chapter 1 COMP 2610 Dr. James Money COMP 2610

2. How We Will Get There Dr. James Money COMP 2610 • Computer: electronic genius? • NO! Electronic idiot! • Does exactly what we tell it to, nothing more. • Goal of the course: • You will be able to write programs in Cand understand what’s going on underneath. • Approach: • Build understanding from the bottom up. • Bits  Gates  Processor  Instructions  C Programming

3. Two Recurring Themes Dr. James Money COMP 2610 • Abstraction • Allows us to be more productive • Can drive a car without knowing how the internal combustion engine works. • …until something goes wrong! • Where’s the dipstick? What’s a spark plug? Do you understand how a car works? • Important to understand the components and how they work together.

4. Two Recurring Themes Dr. James Money COMP 2610 • Hardware vs. Software • Most people refer to themselves as one who specializes in hardware or software, but not both • You should take the opposite approach – it is good to know both and sometimes essential • Hardware engineers added MMX instructions for video when this did not exist yet • Sorting can be dependent on the underlying hardware • You are seen as more versatile if you know both

5. Computer Systems Dr. James Money COMP 2610 ca 2000 You can see why they called this CPU a microprocessor! ca 1980 It took 10 of these boards to make a Central Processing Unit

6. Computer Systems Dr. James Money COMP 2610 • When we mention computer systems, most people do not only think of the CPU. • It usually includes the keyboard, mouse, monitor, video card, hard drive, and so on • We focus on the CPU and how it does what we want it to do

7. Two important concepts Dr. James Money COMP 2610 • All computers, given enough time and memory,are capable of computing exactly the same things. They are Universal Computing Devices = = PDA Workstation Supercomputer

8. Two important concepts Dr. James Money COMP 2610 • Problem Transformation • The ultimate objective is to transform a problem expressed in natural language into electrons running around a circuit!

9. Computers as Universal Computing Devices Dr. James Money COMP 2610 • Mathematical model of a device that can performany computation – Alan Turing (1937) • ability to read/write symbols on an infinite “tape” • state transitions, based on current state and symbol • Every computation can be performed by some Turing machine. (Turing’s thesis)

10. Tmul Tadd a,b ab a,b a+b Turing machine that multiplies Turing machine that adds Turing Machines Dr. James Money COMP 2610 For more info about Turing machines, see http://www.wikipedia.org/wiki/Turing_machine/ For more about Alan Turing, see http://www.turing.org.uk/turing/

11. Universal Turing Machine Dr. James Money COMP 2610 • Also known as a Universal Computational Device: a theoretical device that accepts both input data and instructions as to how to operate on the data

12. Computers as Universal Computing Devices Dr. James Money COMP 2610 • U is programmable – just like a computer! • instructions are the input data • a computer can emulate a Universal Turing Machine • A computer is a universal computing device.

13. From Theory to Practice Dr. James Money COMP 2610 • In theory, computer can compute anything that’s possible to compute given enough memory and time • In practice, solving problems involves computing under constraints. • time • weather forecast, next frame of animation, etc • cost • cell phone, automotive engine controller, etc • power • cell phone, handheld video game, etc

14. Transformations between layers Dr. James Money COMP 2610 Problems Algorithms Language Instruction Set Architecture Microarchitecture Circuits Devices

15. Statement of Problem Dr. James Money COMP 2610 • We describe the problem initially in natural language • This is inefficient • There are ambiguities in the description normally • “Stir until soup is thick” has multiple meanings to different people • We cannot have this ambiguity in computer programs • We need precision

16. Algorithm Dr. James Money COMP 2610 • In order to make the problem precise, we turn it into an algorithm • This process is called software design • We choose algorithms and data structures • An algorithm is a step by step procedure that is guaranteed to terminate such that each step is precisely stated and can be carried out by a computer. • There are three terms for these properties.

17. Algorithm Dr. James Money COMP 2610 • Definiteness – each step is precisely stated • Effective Computability – each step can be carried out by a computer. For example, you cannot ask a computer to find the largest prime number. • Finiteness – the algorithm terminates.

18. Algorithm Dr. James Money COMP 2610 • There are many algorithms for each problems. • There may be one with the fewest steps • Others may allow concurrent computations

19. Program Dr. James Money COMP 2610 • We now using programming to convert the algorithm to a program • Programming languages are precise and invented to specify a sequence of instructions to the computer • Over 1000 languages • There are two types of languages: • High level – C,C++,Pascal, Java • Low Level – Assembly, one language for each computer type

20. Instruction Set Architecture(ISA) Dr. James Money COMP 2610 • Next, by compiling, we convert the programming language into the instruct set of the computer, called the ISA • The ISA specifies what instructions the computer can perform, what values it needs, and it’s results • We use the term operand to describe the values the instruction needs • The ISA specifies acceptable representations for operands called data types • The ISA also specifies where the operands are located called the addressing modes

21. Microarchitecture Dr. James Money COMP 2610 • Processor design results in the microarchitecture that runs the ISA • The microarchitecture is the detailed particular implementations of the ISA • There are many microarchitectures for each ISA • Intel, AMD for x86 • Different models of Intel chips

22. Logic Circuit Dr. James Money COMP 2610 • We now implement the microarchitecture using simple logic circuits • Here there is a cost tradeoff between cost and performance • NOT gates are cheaper than regular ones • Many choices just for a simple case of addition • This is called the logic circuit design phase

23. Devices Dr. James Money COMP 2610 • Finally, process engineering and fabrication results in the devices used to build the logic circuits • There might be CMOS, NMOS, and other types of circuits.

24. Solve a system of equations Jacobi iteration Gaussian elimination Red-black SOR Multigrid FORTRAN C C++ Java PowerPC Intel x86 Atmel AVR Centrino Pentium 4 Xeon Ripple-carry adder Carry-lookahead adder CMOS Bipolar GaAs Putting it together Dr. James Money COMP 2610 Tradeoffs: cost performance power (etc.)

25. Course Outline Dr. James Money COMP 2610 • Bits and Bytes • How do we represent information using electrical signals? • Digital Logic • How do we build circuits to process information? • Processor and Instruction Set • How do we build a processor out of logic elements? • What operations (instructions) will we implement? • Assembly Language Programming • How do we use processor instructions to implement algorithms? • How do we write modular, reusable code? (subroutines) • I/O, Traps, and Interrupts • How does processor communicate with outside world? • C Programming • How do we write programs in C? • How do we implement high-level programming constructs?