Week 1 Lecture Material

Penn State University

CMPSC 201 – C++ Programming for Engineers

Original class notes from Dough Hogan,

http://www.personal.psu.edu/djh300/index.htm

Computer Science Theory & Introduction

Hardware vs. SoftwareHardware :

physical components of a computer systemessentially, things you can touchinput, output, storage devices

Software : A collection of computer programs and its related

data that provides the instructions telling a computer what to do!

In contrast to hardware, software "cannot be touched“!

0s and 1s : Owing to its straightforward implementation in digital electronic circuitry using logic gates, the binary system is used internally by all modern computers.

Hardware vs. Software

Application Software

System Software

Hardware

Components of a ComputerCentral processing unit (CPU)MemoryInput devicesOutput devicesStorage devices

Central Processing Unit (CPU)Basic job: handle processing of instructions

What’s an instruction?

Two parts:Control Unit (CU) Arithmetic and Logic Unit (ALU)

The ALUBuilt up from digital logic gates

ANDORNOTmost primitive level

MemoryHolds programs that are currently

running and the data being used by those programs.

Two categories:Read-only memory (ROM)

can only read dataRandom-access memory (RAM)

can read and write informationprimary storage - computer’s main memoryvolatile

Sequential Access vs. Random AccessSequential Access:

must access each location in memory in order

Random Access: can access memory locations using addresses, in any order

Speed implications?

Track 1

Track 2

Memory: sizesbase unit: 1 bit = binary digit, 0 or 18 bits = 1 byte (B)1000 bytes ≈ 1 kilobyte (KB)1000 KB ≈ 1,000,000 B ≈ 1 megabyte

(MB)1000 MB ≈ 1,000,000,000 B ≈ 1 gigabyte

(GB)

Storage DevicesFloppy disk

3.5 inches, 1.44 MBHard disk

typically sizes in GBCompact disc (CD)

650-700 MBCD-ROM: read-only memoryCD-R: recordableCD-RW: rewritable

More Storage DevicesDigital Versitale/Video Disc (DVD)

4.7 GBFlash drives

variesZip disks and tape drives

varies

Input Devicesmousekeyboardscannercameramicrophone

Output Devicesmonitor

cathode ray tube (CRT)liquid crystal display (LCD)

printerspeakers

Software OverviewSystem software

Controls basic operations of computerThe operating system

manages memory, files, application softwareFile management tasks – deleting, etc.

Software OverviewApplication software

Not essential to system runningEnables you to perform specific tasksEx:

Office softwareWeb browsersMedia playersGames

Algorithms and Languages

AlgorithmsAn algorithm is a set of instructions to solve a

problem.Think recipes!

Many algorithms may solve the same problem!How do we choose between them?

The answer is that:Different Algorithms differ in the time and the space

they take to run!we choose the most efficient algorithm according to

our resources! (space and time)Example: You may have a lot of memory and your only

concern is how fast the program runs, or the other way around.

Programming Paradigms/Models

Procedural Programming: specify steps to solve problem, use procedures to implement those stepsProcedures are called methods in C++

Object-Oriented Programming (OOP): create objects to model real-world entities. e.g. an employee object

As in real world each object has its ownInformation: (represented by data types)Behaviors: (implemented by methods/procedures)

Objects can interact, as they do in real world Event-Driven Programming: create methods that

respond to events like mouse clicks, key presses, etc.

Others: Functional, logic, etc.

Compiling Process

Source Code(C++)

ObjectCode

ExecutableProgram

ObjectCode fromLibraries

compiler linker

Compiler is a software that transforms a source code written in one programming language into a program in another language (usually machine language, a language than can be executed by CPU)

Code in machine language

linker :A program that takes two or more object files generated by a compiler and combines them into a single executable program.

Source Code(C++)

ObjectCode

ExecutableProgram

ObjectCode fromLibraries

compiler linker

Library has been complied before! , it won’t need to be compiled every time.

ObjectCode fromLibraries

Source Code of library

(C++)compiler

Compiled vs. Interpreted Languages

Interpreted LanguageRequires software

called an interpreter to run the code

Code is checked for errors as it runs (if erroneous code: does the best it can…)

Examples: HTML, JavaScript, PHP

Compiled LanguageRequires software called

a compiler to translate the program into (usually) an executable program with machine language

Syntax errors will be found during compilation

code will be syntax-error free while executing (running)

Examples: C, C++, Pascal, FORTRAN, BASIC

ErrorsSyntax Errors

Much like using incorrect punctuation or grammar in English

Compiler reports syntax errors; program won’t run until they’re resolved

Logic Errors Program doesn’t solve the problem correctlyIt May be correct syntactically, but it is not doing

what is supposed to do (according to specification of program)!

Runtime ErrorsErrors that occur while the program is running,

e.g. problems accessing memory, divide by zero

AbstractionAbstraction

Abstraction is a fundamental concept to CS

Principle of ignoring details , so that by focusing on more general

concepts we are able to use complex devicesFocusing on the WHAT, rather than HOW

Example: Abstract of a paper!Example: Your report template!

Levels of Abstraction0. Digital Logic1. Machine Language

A system of instructions, that are executable directly by the CPU.

Every CPU has an instruction set architecture (ISA) of its own!

2. Operating System3. Low-Level Language

Low refers to small or no amount of abstraction from machine language. e.g. Assembly language

4. High-Level Language High refers to strong abstraction from the details of the CPU

designUses natural language elements, thus it’s easier to

understand

5. Application Software

Binary NumbersUse two symbols: 0 and 1 to represents

numbersBase 2Compare with decimal number system

Uses symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 to represents numbers

Base 10

At the lowest level of abstraction, everything in a computer is expressed in binary.

Binary Numbers, ctd.

0 0 1 1

10 211 3

100 4

101 5110 6111 7

1000 81001 9

1010 101011 111100 121101 131110 141111 15

10000 16

Binary Numbers, ctd.

0 0 1 1

10 211 3

100 4

101 5110 6111 7

1000 81001 9

1010 101011 111100 121101 131110 141111 15

10000 16

1 1 + 1_____________________

1 0 0

1 0 0 0 + 1_____________________

1 0 0 1

Convert Vs. Decimal

Other Number SystemsAny positive integer could be the base of a

number system. (Big topic in number theory.)

Others used in computer science:Octal: Base 8Hexadecimal:

Base 16New symbols A, B, C, D, E, F

Example of machine language instructions

At the lowest level of abstraction, everything in a computer is expressed in binary.

This is an example of an ‘Add’ instruction: 000000 00001 00010 00110 00000 100000

Couple of more examples of machine language instructions:100011 00011 01000 00000 00001 000100000010 00000 00000 00000 10000 000000

Hello World Example in Assembly Language

.model small

.stack

.datamessage db "Hello world, I'm learning Assembly !!!", "$".codemain proc mov ax,seg message mov ds,ax mov ah,09 lea dx,message int 21h mov ax,4c00h int 21hmin endpenad main

ASCIIEvery character on a computer -- letters,

digits, symbols, etc. -- is represented by a numeric code behind the scenes.

ASCII is a character-encoding scheme based on the ordering of the English alphabet

Short for American Standard Code for Information Interchange.

Most modern character-encoding schemes are based on ASCII, though they support many more characters than does ASCII.

We’ll learn more in lab…

Moor’s Law

# Transistors on a ProcessorProcessor Date Number of Transistors

4004 1971 2,250

8008 1972 2,500

8080 1974 5,000

8086 1978 29,000

286 1982 120,000

386 1985 275,000

486 DX 1989 1,180,000

Pentium 1993 3,100,000

Pentium II 1997 7,500,000

Pentium III 1999 24,000,000

Pentium 4 2000 42,000,000

Data forIntel processors:

Data from Section 4.1 of :

Yates, Daniel S., and David S. Moore and Daren S. Starnes. The Practice of Statistics. 2nd Ed. New York: Freeman, 2003.

A Graphical View

Graph from Intel's web site (http://www.intel.com/technology/mooreslaw/index.htm); Retrieved 9/24/2006

Pay attention to the units on the axes…

Moore’s LawPrediction from Gordon Moore of Intel in

1965.Implication: The speed of processors

doubles roughly every 12 to 18 months. Can this go on forever?