Computer Systems

TexPREP Summer CampComputer Science

All those parts of a computer that you can see and touch.

Programs (set of instructions) and data.

Computer SystemHardware

Computer SystemSoftware

www.coolnerds.com/Newbies/Hardware/hardware.htm

Hardware

http://www.antonine-education.co.uk/ict_as/ict_module_2/topic_8/computer_architecture.htm

Computer

Hardware

The two most important components of a computer are:

• CPU: Central Processing Unit• Memory: typically RAM (Random Access

Memory) They are connected by the system bus and are

located on the motherboard.

CPU

The CPU is the “brain” of the computer.

• It gets an instruction from main memory and then executes it.

• If the instruction needs some data, it gets the data from main memory in order to process it.

• After executing the instruction, if there is a result that needs to be saved, it stores the result on main memory.

These steps are repeated for each instruction in the program.The speed of the processor is expressed in Gigahertz (GHz).

Memory

There are different types of memory in a computer system.• Main memory (RAM): where programs and data must be

loaded in order to be processed.

• ROM: where the boot (startup) program is stored.

• Cache: very high speed memory used to improve the performance of the system.

The amount of memory is typically expressed in Megabytes (MB), Gigabytes (GB), or Terabytes (TB).

RAM and Cache are volatile, that is, they lose their content when the power is turned off. ROM is not volatile.

Their access time is in the order of nanoseconds (0.000000001 seconds)

System Clock

The components of the computer must interact in a synchronized way.

A system clock is used to control the timing of all computer operations.

It generates regular “ticks” (electronic pulses) that set the operating pace of the components.

Its speed is expressed in Megahertz (MHz) or Gigahertz (GHz).

Peripheral devices

• Storage devices: used to store data and programs permanently (non volatile). For example: hard drive, flash drive, cd drive, etc.

• Input devices: used to enter data and instructions (programs, commands, etc.) into the computer. For example: keyboard, mouse, microphone, scanner, etc.

• Output devices: used to get information from the computer. For example: monitor, printer, speakers, etc.

Storage devices

The three main technologies are:

• Magnetic: used on hard disks, tape, etc.

• Optical: used on CDs (ROM, R, RW), DVDs (R, RW, RAM), etc.

• Solid state: used on flash drives, memory cards, etc.

Hard drive

http://www.pctechguide.com/31HardDisk_Construction.htm

laserdiode

laserdiode

prism prism

light-sensing

diode

light-sensing

diode

0 1

lens lenspit land

disc label

Optical Discs

Discovering Computers 2006, Course Technology, p. 367 Fig. 7-20

Step 1.Laser diode shines a light beam towarddisc.

Step 2.If light strikesa pit, it scatters. If light strikes a land, it is reflected back toward diode.

Step 3.Reflected light is deflected to alight-sensing diode, which sends digital signals of 1 to computer. Absence of reflected light is read as digital signal of 0.

Adapter Cards

Also known as expansion boards, are used to increase the capabilities of a computer.

They must be inserted in expansion slots and their respective device drivers installed before they can be accessed by the system.

There are different technologies: PCI, AGP, etc.

Motherboard

http://www.washington.edu/lst/help/computing_fundamentals/troubleshootingxp/hardware

Adapter Cards examples• video adapters

• graphics accelerators

• sound cards

• accelerator boards

• NIC - network interface card

Graphics Adapter Card

http://salestores.com/stores/images/images_747/P65MDDE128LPUF.jpg

Units of measurement

KILO: 1,000 or 103

MEGA: 1,000,000 or 106

GIGA: 1,000,000,000 or 109

TERA: 1,000,000,000,000 or 1012

Inside the computer…Everything is discrete (digital), not continuous (analog) – i.e, it must be represented using a discrete (number) value

Problem: How do we put the analog world “inside” the digital computer?

Solution: Devise ways to represent real-world, analog data in digital forms

Digital Representation

Computers have storage units called binary digits or bits

The computer operates with voltage through what amounts to microscopic switches that are either “On” (1) or “Off” (0)

Low Voltage = 0High Voltage = 1 all bits have value 0 or 1

What do computers work with internally?

Representing Numbers

Binary number system

Representing CharactersASCII (American Standard Code for Information

Interchange) and Unicode