ISYS 101Lecture #11 Intro to Information Systems I Computer Functions and Hardware ISYS 101 Glenn Booker

ISYS 101 Lecture #1 1

Intro to Information Systems IComputer Functions and Hardware

ISYS 101

Glenn Booker


Syllabus

• This course covers the most important concepts of how computers do stuff and talk to each other

• Be sure to attend every class, and come prepared – after this one, the lectures should be a review to help clarify what you’ve read

• Don’t forget: http://users.snip.net/~gbooker/


Who am I?

• I have over 15 years of experience in software development, primarily for Department of Defense (DOD) and Federal Aviation Administration (FAA) projects

• I tend to ramble, so PLEASE STOP ME if you get lost or have a question


Who are you?

• What’s your name?

• Where do you work, and what do you do?

• Are you comfortable:– With word processing and email?– With surfing the Internet?– With spreadsheets and writing presentations?– Have you published a web site before?


Omnipresent Computers

• Computers are everywhere in our society– Cars, airplanes– Appliances– Street signals– Toys, etc.

• Computers do exactly what we tell them very quickly – no more, no less


What Do Computers Do?

• Computers exist to do four things:– Accept some kind of input– Do some sort of processing on that input– Generate output– And store data

• Together, these things constitute the information processing cycle


What Computers Can’t Do

• So far, computers can’t have emotion, tell themselves what to do, or be creative

• Computers only do what their programs have told them to do – are otherwise stupid

• Programs tell the computer what functions to perform, and in what order to do them (an algorithm – kind of like a recipe)


Our Responsibility

• Computers have no sense of correct or ethical, so we have to perform that function through the algorithms we write and the quality we build into the software

• Particularly important for software which might affect life (safety-critical) and software which runs your business (mission-critical)


Computer Hardware

• Essential pieces of computer hardware include:– The system unit (“CPU box”), including the

floppy drive and CD-ROM or DVD-ROM– Monitor (output)– Keyboard (input)– Mouse (input)


Computer Hardware

• Multimedia hardware includes– Speakers and subwoofer (output)– Microphone (input)

• And talk to other computers via– Modem (input or output)– Network connection (input or output)

• Outputs can also be to a printer


System Unit

• The “system unit” also includes everything else required for normal use of the computer, typically including:– Motherboard, Central Processing Unit (CPU),

and Random Access Memory (RAM)– Hard drive(s)– Sound card, network card, and video card


Sizes of Computers

• Personal computers are most familiar, but computers can range from chip-sized to massive multi-million dollar beasts

• Servers, from workgroup servers to enterprise servers, serve groups of computers, and are otherwise not generally used directly by individuals


Software

• … is needed for computers to do anything

• It is written in a programming language in the readable form called source code

• Source code is “compiled” to create object code

• Object code is linked to form executable code – the programs you run are executable


System vs Application Software

• System software is needed for the computer to function as a computer– Includes the operating system, which manages

memory, writes files, and other basic chores, e.g. Microsoft Windows, Linux, MacOS

• Application software is the program used for a particular purpose– Microsoft Word, Lotus Notes, Internet Explorer


The Internet

• … is a global network of computers which all speak a common set of languages (the TCP/IP protocols)

• Most access the Internet via a service provider (ISP)

• Main applications are email and the WWW

• Commerce applications are increasing


Bit and Bytes

• Bit (b) is a ‘binary digit’, namely 0 or 1– Data transfer rates, such as across a network, or

from a modem, are measured in bits per second

• A group of 8 bits is a byte (B)– One byte can describe a single character– Storage is measured in bytes; a page of text

might be around 1400 bytes of data– Half of a byte is called a nibble


Big Numbers Abound!

• 1 kB = 1 kilobyte = 210 bytes = 1024 bytes

• 1 MB = 1 megabyte = 220 bytes = 10242 bytes

• 1 GB = 1 gigabyte = 230 bytes = 10243 bytes

• 1 TB = 1 terabyte = 240 bytes = 10244 bytes

• But many cheat and just use thousand, million, billion, and trillion instead


History of Computing

• While some forms of data storage and computation go back centuries (abacus), electronic digital computers only go back to 1946 (ENIAC)– 4800 times faster than hand calculations

• Programs were wired manually - later computers stored programs on punched paper cards


History of Computing

• Four generations of computers so far– First used vacuum tubes and were programmed

in machine language (’50s)– Second used transistors and programming

languages (’60s)– Third used integrated circuits and timesharing– Fourth uses microprocessors and graphical

interfaces (’80s to now)


Microprocessors

• Microprocessors take lots of circuit elements (transistors) and put them all in one very small chip

• A CPU is the most familiar microprocessor– Intel 4004 (1975) had 2200 transistors– Intel Pentium 4 (2000) has 42 million

transistors, and weighs less than an ounce


Microprocessors

• Microprocessors’ activities are controlled by their clock - the faster the clock, the more a processor can get done

• Early CPU speeds were in kilohertz (1000’s of cycles per second); now typically well above 500 MHz (megahertz, millions of cycles per second)


Microprocessors

• Microprocessors’ speed is also affected by their architecture– CISC (complex instruction set computing) had

to get the most from a few big instructions– RISC (reduced instruction set computing) runs

smaller instructions much faster– EPIC (Explicitly Parallel Instruction

Computing) might improve on RISC


Microprocessors

• Microprocessors are limited by their word size – affects operating system choices– 8-bit (Intel 8088), MS-DOS– 16-bit (Intel 286), Windows 3.11, 95/98/ME– 32-bit (Intel 386-Pentium 4, G3, G4), Win NT,

Linux– 64-bit (DEC/Compaq Alpha, Intel Itanium),

some Windows 2000, Unix’es and Linux


Microprocessors

• Dominant microprocessors now are– Intel Pentium III and 4

• Xeon versions for servers

– AMD Athlon and Duron– Motorola/IBM G3 and G4 (used in

Macintoshes and Unix workstations)

• Just released is the Intel Itanium, for servers


History of Programming

• Each computer has its own assembly language for manipulating data

• Programming languages evolved to make programs easier to write and maintain – independent of the assembly language

• Fortran, Basic and Cobol were the earliest

• Later, C and Pascal were widely used


History of Programming

• There are thousands of programming languages ; the most popular languages today include– C, C++, and Java– Basic– Cobol– And lesser known languages, such as Ada, Perl,

Smalltalk, C sharp (C#), etc.


Next Programming Generation?

• Programming has evolved little in the last decade or so

• Object oriented methods have matured, but haven’t replaced procedural programming

• Artificial intelligence is maturing

• Distributed systems are becoming more common


Inside the System Unit

• Now let’s dive into computer hardware in a little more detail, and then see how it works together

• The system unit includes cooling fans and a power supply– Most devices have separate connections for

power (separate wires), and data (a flat ribbon)


Motherboard

• The heart of the computer is motherboard, which holds the CPU (e.g. Pentium III and 4, Athlon, G3, and G4) and RAM

• The CPU is either mounted on a card in a slot, or in a socket with hundreds of pins

• The type of slot or socket determines what kind of CPU can be used


Random Access Memory

• The CPU uses RAM to run system and application software

• RAM is mounted in two to four slots– Each RAM stick typically holds 64 MB to

512 MB of RAM – Many kinds of RAM (PC100, Rambus, DDR,

SIMMs, DIMMs, etc.)


Cache Memory

• In addition to RAM, a CPU uses temporary storage called cache memory

• Usually there are two caches, primary (L1) and secondary (L2)

• Caches are very small (e.g. 8 kB L1 and 256 kB L2)

• Bigger caches are better


Typical Modern Motherboard

4 RAM slots

5 PCI slots

AGP slot CPU socket

This edge sticks out of the system unit

Electrical stuff!

ASUS P4T


Bus Speeds

• The CPU communicates with everything else (slots and ports) across a “bus”

• The faster the bus, the faster the computer

• Typical Pentium, G3, and G4 bus speeds are 66, 100, or 133 MHz

• Athlon bus speeds are 200 or 266 MHz

• Pentium 4 pretends to have a 400 MHz bus


Motherboard Sizes

• There are several families of motherboard sizes (which also drives the case size)

• AT (Baby AT, Full AT) for smaller personal computers

• ATX (microATX, Full ATX, Server ATX) for most PC’s and workstations

• WTX, for servers


Integrated Motherboards

• Some motherboards build in functions– Sound– Video– Network connection– SCSI controller

• This may save money initially, but reduces future expandability


Motherboard Slots

• Motherboards have PCI slots which are typically used for– Network card, Sound card, Modem– SCSI card (for other drives)– Older computers have the video card in a PCI

slot

• Older PC’s have ISA or EISA slots


Other Motherboard Connections

• Older other ports on a motherboard are– Keyboard and mouse ports (PS/2)– Serial (ext. modem) and Parallel (printer) ports

• They’re being replaced by– USB (Universal Serial Bus) ports, 12 Mb/s– Fire Wire (IEEE 1394) ports are rare, but faster

than USB, 400 Mb/s


Motherboard Summary

• So the motherboard choice determines– How big the system unit is (case size)– How much RAM may be installed (by the

number and type of RAM slots)– What how many and what kind of cards can be

installed (PCI, AGP, ISA, etc.)– What kinds of CPU can be used– And hence what operating systems may be used


Video

• The monitor is controlled by a video card, which goes in an AGP slot

• Accelerated Graphics Port (AGP) slots are in the original speed, 2x, 4x, and Pro speeds

• Video cards have their own kind of RAM and processors to help determine what gets send to the monitor


Storage Devices

• “ROM” devices are Read Only Memory – you can only read their data (music CD’s)

• CD-R devices can also Write CD’s, but only once (CD “burner”)

• CD-RW and DVD-RAM devices can read and write from a disc many times, making them like big floppies


IDE Storage Devices

• Most personal computers currently use IDE hard drives, CD, and/or DVD drives

• They’re cheap and reasonably fast

• Limited to four devices on most computers

• The floppy drive doesn’t count against that limit – it’s on its own controller


SCSI Storage Devices

• SCSI storage devices are typically faster and much more expensive than IDE equivalents

• Up to 7 or 15 SCSI devices can be linked

• Larger capacities available, and somewhat more reliable than IDE

• Used for servers and workstations


SCSI Storage Devices

• SCSI devices have evolved over 20 years from a transfer rate of just over 1 Mb/s (megabit per second) to 320 Mb/s

• SCSI types include SCSI-1, -2, and –3, Fast, Wide, and Ultra

• SCSI connectors have 25, 50, 68, or 80 pins


IDE and SCSI Speeds

• Common peak IDE transfer speeds are 33, 66, and 100 Mb/s

• SCSI transfer speeds run 20, 40, 80, 160, and 320 Mb/s


What to Expect on a PC?

• Typical amounts of RAM range from 128 to 512 MB, but some can handle 2 GB+– RAM costs about 25¢ to $1 per MB, depending

on its type

• Typical hard drives range from 10 to 80 GB– Hard drives cost from about $4 to $8 per GB

for IDE drives, $10 to $15 per GB for SCSI


Data Representation

• Most computers are digital (1’s and 0’s)

• Analog computers exist – they solve problems by replicating equations with electricity

• We use base 10 for counting

• Computers use base 2 (binary), eight (octal), or 16 (hexadecimal) internally


Characters

• The Latin alphabet was initially represented by the ASCII character set (128 letters, numbers, and symbols) using 7 bits of data

• IBM also used EBCDIC

• Unicode is the new standard for representing any language, using 16 bits per character (65,536 possible symbols)


Storage Volatility

• RAM and cache memory are volatile storage – when the computer is shut off, they become empty

• Most other storage devices (hard drives, etc.) are non-volatile – when the computer is shut off, they remember what was stored


Non-Volatile Storage Devices

• Non-volatile storage devices include– Floppy drives– Hard drives– Removable media drives (Zip, Jaz, optical, etc.)– CD-ROM, CD-R, CD-RW drives– DVD-ROM, DVD-RAM drives– Backup tape drives (DAT, DDS, QIC, DLT)


Sequential vs. Random Access

• Most storage devices allow easy access to any random piece of data – hence are random access devices

• Most backup tape drives only allow access to one piece of data at a time, and must rewind the tape to see others – sequential

• Access times for sequential devices is slow!


Storage Density

• 1960’s ½” magnetic tape held 1600 bits/in.– That’s 400 bytes/square inch

• Data density of 15 GB on one 3.5” platter is now in production– That averages 800,000,000 bytes/square inch

• Look for another factor of ten improvement soon


Floppies

• 3.5” Floppies hold 1.44 MB of data

• They are descended from 5.25” and 8” floppies, which were really floppy

• Fast becoming obsolete, as bootable CD’s become more common (like workstations)

• 20 MB and 120 MB floppies exist, but are little used


Magnetic Drives

• Magnetic drives (from floppies to SCSI hard drives) read and write data by passing a magnetic head above the surface of the disk

• A head crash is when the head physically hits the disk – very bad!

• Optical drives use lasers to read and write


Hard Drive Terms

• Hard drives are described by capacity and:– Spindle speed (3600, 5400, 7200, 10,000, or

15,000 rpm)– Interface type (IDE (=ATA) or SCSI) & speed– Access speed (given in milliseconds):

IDE are around 8 ms, SCSI can go under 5 ms– MTBF (mean time between failure) which can

be over 1 million hours


RAID

• RAID arrays take several identical hard drives, and use that to get redundancy and/or more speed

• RAID 0 is striping, which adds speed but has no redundancy

• RAID 1 is mirroring, which creates a pair of identical copies of everything


RAID

• RAID 5 balances speed and redundancy by spreading a little of each data across all disks – effectively “losing” only one drive

• RAID 0, 1, and 5 can be combined

• RAID is often combined with hot-swap ability; the ability to remove a drive safely from a working system and replace it


Backup Solutions

• Magnetic tape is still useful for backups

• Problem is that storage is now cheaper than the backup drives!

• CD’s (and soon DVD’s) are often used for backup

• Magneto-optical (MO) and write once read many (WORM) drives were popular


Input Devices

• The (typing) keyboard is the most common input device

• A mouse (or trackball) is required for most operating systems– Mice use serial, PS/2, or USB interface

• A microphone can be used for voice or other sound input


Input Devices

• Cameras are increasingly popular for analog or digital video input

• Scanners are frequently used for images or scanning text using optical character recognition (OCR)

• Laptop computers might use a pointing stick or touchpad instead of a mouse


Input Devices

• Games might use a joystick

• Touch screens, like seen on MAC machines are possible but pricey

• Artists can use tablets, like those by Wacom

• Video can be input from cameras in either analog or digital form

• Still digital cameras can also provide input


Input Devices

• Faxes can be inputs to a computer (often through the modem)

• Special scanners can read bar codes

• Bio inputs, such as fingerprints or eye scans can be used for identification

• There’s no shortage of inputs!


Output Devices

• Types of output devices are similar to inputs– Text– Graphics– Sound– Video

• Text and graphics are most commonly output to a visual display system (monitor)


Monitors

• Monitors are judged by several traits– Screen size (15”, 17”, 19”, 20”, 21”, and up)– Resolution (number of pixels wide and high);

640x480, 800x600, 1024x768, 1280x1024, etc.– Dot pitch (0.28 mm is bad, 0.25 mm or less is

better, especially for big screens)– Refresh rate (how many times the screen is

redrawn per second) want 75 Hz or more


Monitors

• Monitors used to all be cathode ray tubes (CRT), like a TV

• LCD “flat panel” monitors are the rage, but much more expensive

• Projectors show video output to an external screen or wall

• Head-mounted displays serve one person!


Video Cards

• Video cards are mainly judged by the resolution size, color resolution, and refresh rate can be sustained

• Some also have special processors for 3D graphics

• Color resolution is given in bits per pixel, or the number of colors


Video Color Resolution

• 4 bit = 16 colors “VGA”

• 8 bit = 256 colors

• 16 bit = 65,536 colors “thousands” or “high color”

• 24 bit = 16,777,216 colors “millions”

• 32 bit = 4,294,967,296 colors “true color”


Printers

• Most familiar are ink jet printers and laser printers– Ink jets are cheap, can do good color, but are

slow– Laser printers are much faster, some are color,

but are pricey

• Impact printers can create carbon copies, like the 9- or 24-pin dot matrix printers


Printers

• Professional printers use dye sublimation printers ($$$$$)

• Drafters use plotters, which can use pens, ink jets, or lasers

• Other special purpose printers use these same technologies, like label printers


Multimedia Output

• Music output can be to speakers, or to MIDI devices

• MIDI (Musical Instrument Digital Interface) allows pro sound gear to communicate with computers

Documents

ISYS 101Lecture #11 Intro to Information Systems I Computer Functions and Hardware ISYS 101 Glenn Booker