Transcript CPS120 - Washtenaw Community College

CPS120: Introduction to
Computer Science
Introduction to Computers
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
History of Computers
 Abacus
 Pascal’s 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.
"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 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
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 9X, MS-DOS, OS/2, MacOS, Unix, Linux,
BeOS
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
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 textbased
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
Data Representation
 Objectives
– Understand how data & instructions are stored
in the PC
– Understand the basics of the binary numbering
system
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 (23)
 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
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