# CPU Components

## General purpose Registers

• Register
• A synonym for memory in computer science
• General purpose reigster
• A memory cell
• Each general purpose register has a unique name
• It is used to
• store (and recall) intermediate result of complex computations

## Arithmetic and Logic Unit (ALU)

• It is a complex electrical circuit that can perform Mathematical (+,-,x,/) and logical operation (<, <=, >, >=, and, or)
• The output (result) of the computation (obtained by the ALU) is often stored in a general purpose register

## Instruction Register (IR)

• Contains the current instruction being executed by the CPU
• The CPU will perform the operation indicated by the instruction code contained in the instruction register

## Program Counter (PC)

• The program counter is a register (memory cell)!
• This register contains the address (location in memory) of the next instruction after the CPU finishes executing the current instruction in the instruction register
• The value in the program counter will be increased after the CPU finishes executing one instruction

## Processor Status Register (PSR)

• This register contains the various information about the CPU.
• Among the information contained in the PSR is
• The result of a comparison operation
• When the CPU compares 2 numbers a and a and b,  the outcome of the comparison is stored in the PSR
• The outcome of a compare operation will allow the CPU to determine the following fact between a and b.

## Reference

[1] http://www.mathcs.emory.edu/~cheung/Courses/170/Syllabus/01/intro-computer2.html

1. Amazon EMR
Amazon Elastic MapReduce (Amazon EMR), it distributes the computational work across clusters of virtual servers running in the Amazon cloud using Hadoop

• It users a distributed processing architecture called MapReduce in which a task is mapped to a set of servers for processing.
• The results of the computation performed by those servers is then reduced down to a single output set.
• One node, designated as the master node, controls the distribution of tasks.

# How to read technical papers in computer science?

From: http://www.cs.iit.edu/~winet/contact.html

How to read technical papers in computer science?
When you read articles or reports, keep the following in mind
• What is the main contribution of the paper?
• Is this important, why?
• Is this a theoretical contribution to some fundamental problems in CS, or a protocol-like contribution, or both?
• What was the main insight in getting the result?
• What is not clear to you?
• What did the authors not do, and you regard important?
• What are the most important assumptions, are they limiting?
• What are the possible applications suggested in the paper?
• How does this relate to other things we have seen?
• What extensions does this suggest?
• Can you suggest some project idea based around the ideas in this paper

# Renewal Process

## Regenerative Process

Stochastic Process Notes, from Lecture 10

### 1. Definition

A stochastic process is a regenerative process if
• Process stochastically starts over at even time
• Times between events are i.i.d

### 2. Regenerative Process v.s. Renewal Process

• A renewal process counts (increasing over time) and has property 2 shown above.
• A regenerative process keeps track of something else and starts over.