CPS120: Introduction to Computer Science Introduction to Computers

 Objectives –Understand the history of computers –Understand the components that make up a desktop PC –Understand the basics of computer architecture –Understand the role of an operating system –Understand the role of assemblers, interpreters, & compilers

5 A mental model that removes complex details This is a key concept. Abstraction

Representing Data  Data can be numeric, alphabetic, or alphanumeric  Computer only uses “on” & “off” within its circuits

Representing Data: Bits  Computer only uses “on” & “off” within its circuits  Binary number system –“On”, 1, high state of electricity –“Off”, 0, low state of electricity –Bits (0’s and 1’s)

Representing Data: Bytes  Byte = 8 bits (2 3 )  256 possible combinations of 8 bits  Decimal system is cumbersome & awkward for pc’s –Can convert from decimal to binary & vice versa ASCII (American standard code for information interchange)  128 characters in the 7-bit set

3 Hardware: The physical elements of a computing system (printer, circuit boards, wires, keyboard…) Software: The programs that provide the instructions for a computer to execute Computing Systems

4 Communication Application Operating System Programming Hardware Data Layers of a Computing System

Early History of Computers  Abacus  Pascal’s gear-driven counting machine (mid 17th Century) –His father was a tax collector  Babbage designed a programmable computer (1834)  Joseph Jacquard designed a loom that used the the punched card to store instructions (late 18th Century)

7 Ada Augusta, Countess of Lovelace First Programmer, the loop (mid 19th Century) Alan Turing (1936) Turing Machine, Artificial Intelligence Testing Harvard Mark I, ENIAC, UNIVAC I Early computers launch new era in mathematics, physics, engineering and economics Early History of Computing

"Modern" Developments  Hollerith built machine for US census bureau & founded IBM (late 19th Century)  1946, ENIAC used vacuum tubes (Univ of Penn) - very hot, needed AC, military paid for this researchENIAC  Transistors used in 1950’s, didn’t burn out like vacuum tubes  Integrated circuits (chips) used in 1960’s  Microprocessor used in 1970’s  Supercomputers, mainframes, minicomputers, workstations, desktop computers

8 Vacuum Tubes Large, not very reliable, generated a lot of heat Magnetic Drum Memory device that rotated under a read/write head Card Readers  Magnetic Tape Drives Development of these sequential auxiliary storage devices First Generation Hardware ( )

9 Transistor Replaced vacuum tube, fast, small, durable, cheap Magnetic Cores Replaced magnetic drums, information available instantly Magnetic Disks Replaced magnetic tape, data can be accessed directly Second Generation Hardware ( )

10 Integrated Circuits Replaced circuit boards, smaller, cheaper, faster, more reliable. Transistors Now used for memory construction Terminal An input/output device with a keyboard and screen Third Generation Hardware ( )

11 Large-scale Integration Great advances in chip technology PCs, the Commercial Market, Workstations Personal Computers were developed as new companies like Apple and Atari came into being. Workstations emerged. Fourth Generation Hardware (1971-?)

12 Parallel Computing Computers rely on interconnected central processing units that increase processing speed. Networking With the Ethernet small computers could be connected and share resources. A file server connected PCs in the late 1980s. ARPANET and LANs  Internet A network of interconnected networks Parallel Computing and Networking

13 Machine Language Computer programs were written in binary (1s and 0s) Assembly Languages and translators Programs were written in artificial programming languages and were then translated into machine language Programmer Changes Programmers divide into application programmers and systems programmers First Generation Software ( )

Representing Instructions:  Low Level Languages –Each computer uses its own machine language –Assembly is a low-level language close to machine language Assembly languages are different on each computer An assembler converts a program into machine language

Machine Languages  different for each computer processor

Assembly Languages  different for each computer processor mainproc pay mov ax, dseg mov ax, 0b00h add ax, dx mov a1, b1 mul b1, ax mov b1, 04h

14 High Level Languages Use English-like statements and made programming easier: Fortran, COBOL, Lisp (artifical intelligence). High-Level Languages Assembly Language Machine Language Second Generation Software ( )

16 Application Package Systems Software High-Level Languages Assembly Language Machine Language Third Generation Software ( )

15 Third Generation Software ( )  Systems Software – utility programs, – language translators, – and the operating system, which decides which programs – to run and when.  Separation between Users and Hardware  Computer programmers now created programs to be used by people who did not know how to program

17 Structured Programming BASIC refined, Pascal, C, C++ New Application Software for Users Spreadsheets, word processors, database management systems Fourth Generation Software ( )

18 Microsoft The Windows operating system, and other Microsoft application programs dominate the market Object-Oriented Design Based on a hierarchy of data objects (i.e. Java) World Wide Web Allows easy global communication through the Internet New Users Today’s user needs no computer knowledge Fifth Generation Software (1990- present)

20 Programmer / User Applications Programmer (uses tools) User with No Computer Background Systems Programmer (builds tools) Domain-Specific Programs Computing as a Tool

21 Computing as a Discipline  Four Necessary Skills 1.Algorithmic Thinking 2.Representation 3.Programming 4.Design

System Components  Hardware –I/O devices (input/output) keyboard, mouse, monitor, etc. –CPU –Primary Storage –Secondary Storage  Software

Computer Architecture  Microprocessor (examples Pentium, Pentium II, PowerPC, etc.) –includes Bus Interface Unit, Arithmetic & Logic Unit (ALU), Control Unit, registers –motherboard is simply the main circuit board that contains most of these parts –the CPU (central processing unit) is considered to be most of these parts taken as a whole  Bus –connects the microprocessor to the RAM & ROM –addresses for data and instructions are important

Storage Devices  Primary storage –RAM (Random Access Memory, or just “memory” for short) active data that is being stored, lost if power is cut off so save often –ROM (Read-Only Memory) commands that are permanently stored on chips PC’s use BIOS, Macs use the Toolbox  Secondary storage –Hard disk, floppy disks –Slower method of storage & retrieval but “safer”

Software: Systems Software  Operating systems –Controls the hardware components (disks, CPU, printers, etc.) –Windows XP, Windows NT/2000, Windows 9- X, MS-DOS, OS/2, MacOS, Unix, Linux, BeOS

Software: Application Software  Office products –Word processors –Spread sheets –Presentation software –  Business applications –General ledger –Financials Accounts payable Accounts receivable –HRMS –Fixed assets/inventory

Programming Software  Text Editor – Used by the programmer while coding the program in a programming language Like a word processor - creates a text file containing the program's instructions or "source code" –Examples are “nled” and “vi” editors in Unix systems –Other editors are NotePad and WordPad which are text- based

Programming Software  Interpreters –Translates source code into machine code line by line  Compiler –Translates source code into an object file, than uses linker to create an executable file A source module (source code) becomes an "object" module (compiled module) Then it is linked with system modules to become a "load" module (linked module)  It is usually more efficient to use a compiler