CIS 212 Microcomputer Architecture Day 6 Rhys Eric

CIS 212 Microcomputer Architecture Day 6 Rhys Eric Rosholt Office: Office Phone: Web Site: Email Address: Gillet Hall - Room 304 718 -960 -8663 http: //comet. lehman. cuny. edu/rosholt/ rhys. rosholt @ lehman. cuny. edu

Chapter 3 Data Representation

Chapter 3 Data Representation Chapter Outline Data Representation and Processing Automated Data Processing Binary Data Representation Goals of Computer Data Representation CPU Data Types – Integer – Real number – Character – Boolean – Memory address Technology Focus: Intel Memory Address Format Data Structures

CPU Data Types • Primitive data types – – – Integer Real number Character Boolean Memory address • Representation format for each type balances compactness, accuracy, ease of manipulation, and standardization

Memory Addresses • Identifying numbers of memory bytes in primary storage • Simple or complex numeric values depending on memory model used by CPU – Flat memory addresses • single integer – Segmented memory addresses • multiple integers • requires definition of specific coding format

Intel Memory Address Formats • 8088 – 20 -bit memory addresses • 4 -bit segment identifier • 16 -bit segment offset • 80286 – 24 -bit memory addresses • 8 -bit segment identifier • 16 -bit segment offset • 80386 – 32 -bit memory addresses • 16 -bit segment identifier • 16 -bit segment offset • 80486 • Pentium

Data Structures • Related groups of primitive data elements organized for a type of common processing • Defined and manipulated within software • Many use pointers to link primitive data components

Commonly Used Data Structures arrays linked lists records tables files indices objects

One Address Finds Many Data Elements

Pointers and Addresses • Pointer – Data element that contains the address of another data element • Address – Location of a data element within a storage device

Arrays and Lists • List – A set of related data values • Array – An ordered list in which each element can be referenced by an index to its position

A simple array is used to store words

Linked Lists • Data structures that use pointers so list elements can be scattered among nonsequential storage locations – Singly linked lists – Doubly linked lists • Easier to expand or shrink than an array

A Singly Linked List

A Singly Linked List

Editing An Array

Editing A Singly Linked List

A Doubly Linked List

Records and Files • Records – Data structures composed of other data structures or primitive data elements – Used as a unit of input and output to files • Files – Sequence of records on secondary storage

A Record Data Structure

Methods of Organizing Files • Sequential – Stores records in contiguous storage locations • Indexed – An array of pointers to records – Efficient record insertion, deletion, and retrieval

An Indexed File

Classes and Objects • Classes – Data structures that contain traditional data elements and programs that manipulate that data – Combine related data items and extend the record to include methods that manipulate the data items • Objects – One instance, or variable, of the class

A Class of Objects

Summary • How data is represented and stored within computer hardware • How simple data types are used as building blocks to create more complex data structures (e. g. , arrays, records) • Understanding data representation is key to understanding hardware and software technology

Chapter Goals • Describe numbering systems and their use in data representation • Compare and contrast various data representation methods • Describe how nonnumeric data is represented • Describe common data structures and their uses

Next Class Tuesday February 21, 2012 Rhys Eric Rosholt Office: Office Phone: Web Site: Email Address: Gillet Hall - Room 304 718 -960 -8663 http: //comet. lehman. cuny. edu/rosholt/ rhys. rosholt @ lehman. cuny. edu