CPS120: Introduction to Computer Science

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CPS120 Introduction to Computer Science

• Introduction to Computers

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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

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History of Computers

• Abacus
• Pascals gear-driven counting machine
• His father was a tax collector
• Babbage designed a programmable computer (1834)
• Ada Augusta King, Countess of Lovelace,
  translates Menabrea's pamphlet on the Analytical
  Engine, adding her own notes, and becomes the
  world's first programmer.

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"Modern" Developments

• Hollerith built machine for US census bureau
  founded IBM
• 1946, ENIAC used vacuum tubes (Univ of Penn) -
  very hot, needed AC, military paid for this
  research
• Transistors used in 1950s, didnt burn out like
  vacuum tubes
• Integrated circuits (chips) used in 1960s
• Microprocessor used in 1970s
• Supercomputers, mainframes, minicomputers,
  workstations, desktop computers

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System Components

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

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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

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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
• PCs use BIOS, Macs use the Toolbox
• Secondary storage
• Hard disk, floppy disks
• Slower method of storage retrieval but safer

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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

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Software Application Software

• Office products
• Word processors
• Spread sheets
• Presentation software
• Email
• Business applications
• General ledger
• Financials
• Accounts payable
• Accounts receivable
• HRMS
• Fixed assets/inventory

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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 emacs and vi editors in Unix
  systems
• Other editors are NotePad and WordPad which are
  text-based

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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

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Data Representation

• Objectives
• Understand how data instructions are stored in
  the PC
• Understand the basics of the binary numbering
  system

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Representing Data

• Data can be numeric, alphabetic, or alphanumeric
• Computer only uses on off within its
  circuits

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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 (0s and 1s)

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Representing Data Bytes

• Byte 8 bits (23)
• 256 possible combinations of 8 bits
• Decimal system is cumbersome awkward for pcs
• Can convert from decimal to binary vice versa
• ASCII (American standard code for information
  interchange)
• 128 characters in the 7-bit set

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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