CS101: Introduction to Computing

1. CS101: Introduction to Computing Fall 2009 Instructors: Badre Munir, Usman Adeel, Zahid Irfan & Maria Riaz Faculty of Computer Science and Engineering GIK Institute of Engineering Sciences and Technology

2. Data Representation

3. Data Representation • Modern computers are digital devices • A digital device works with discrete data, such as the digits 1 and 0 • An analog device works with continuous data • Just as a standard light switch is a simpler technology than a dimmer, so is digital when compared to analog digital analog

4. Number System • We use decimal number system [base 10] when representing numeric values in our daily life • E.g., consider the number 123 • 123 = 100 + 20 + 3 = 1*102 + 2 * 101 + 3*100 • Most modern computer systems do not use the decimal system to represent numeric values. • Instead, they use a binary numbering system [base 2] • Consisting of only two digits: 1 and 0 • Uses powers of 2 rather than 10 • It is said that there are 10 types of people: • those who understand binary, and those who don’t !

5. Conversions • Conversion from binary to decimal: • (1011)2 = 1*23 + 0*22 + 1*21 + 1*20 = (11)10 • Conversion from decimal to binary: 2 16 2 125 2 8 – 0 2 62 – 1 2 4 – 0 2 31 – 0 (16)10 = (10000)2 2 2 – 0 2 15 – 1 (125)10 = (1111101)2 2 1 – 0 2 7 – 1 2 3 – 1 2 1 – 1

6. Representing Non-Numeric Data • Some decimal values & their binary equivalents  • In addition to numeric data, computers also manipulate character data • numbers, symbols, numerals that are not used in arithmetic operations • To represent them, codes have been developed that specify binary equivalent for each character • ASCII – 7 bits [Example table given ] • Unicode – 16 bits • Sounds and pictures must be transformedinto a format the computer can understand • A computer must digitize colors, notes, and instrument sounds into 1s and 0s

7. Quantifying Bits and Bytes • A bit is one binary digit (b): • can have value either 0 or 1 • A byte is 8 bits (B) • 0010 0100 • Kilo- means a 1000; Mega- means million; Giga -means billion • Kilobit (Kb) is 1,024 bits • Kilobyte (KB) is 1,024 bytes • Megabyte (MB) is 1,048,576 bytes • Gigabyte (GB) is 1,073,741,824 bytes • Bits take the form of electrical pulses that can travel over circuits • Almost the same way as electricity flows over a wire when you turn on a light switch

8. Computer Hardware Microprocessor Memory Storage Devices I/O Devices

9. Computer Chips (-1-) • Most electronic components inside a computer are integrated circuits • Thin slices of silicon crystal packed with microscopic circuit elements • Semiconducting materials are used to fabricate a chip • Types of chips: • DIPs; DIMMs; PGAs; SEC cartridge • *The motherboard houses all essential chips and provides connecting circuitry between them

10. Computer Chips (-2-) Dual In-line Memory Module (DIMM) Dual In-linePackage (DIP) PinGridArray(PGA) SingleEdgeContact(SEC)

11. Microprocessor • An integrated circuit designed to process instructions - CPU on a chip • The CPU has two parts • ALU (arithmetic logic unit) • Performs arithmetic operations • Performs logical operations • Uses registers to hold data being processed • Control Unit • Directs and coordinates processing

12. Random Access Memory (RAM) • A temporary holding area for data, application program instructions, and the operating system • As you type, characters are held in RAM • RAM is primary storage (main memory) • Measured in megabytes (MB) or gigabytes (GB) • Today’s computers have between 256 MB and 2 GB of RAM depending on software you use • You can purchase additional RAM • A computer can use disk storage to simulate RAM. This is called virtual memory • Not as fast as RAM

13. Types of RAM • RAM components vary in speed, technology, and configuration • SDRAM (Synchronous Dynamic RAM) • RDRAM (Rambus Dynamic RAM) • DDR • DDR2 • DDR3 • Speed is measured in nanoseconds. • 1 nanosecond (ns) is 1 billionth of a second • It can also be expressed in MHz (millions of cycles per second)

14. Other Types of Memory • Read-Only Memory (ROM) • Type of memory circuitry that holds the computer’s startup routine • Permanent and non-volatile • Only way to change the instructions on a ROM chip is to replace the chip • Additionally, a computer needs a semi-permanent way of keeping boot data • CMOSmemoryholds data but requires very little power to retain its contents • Retains important computer settings after you turn the power off • Can be run by a battery on the motherboard

15. Storage Devices • A storage mediumis the disk, tape, CD, DVD, paper or other substance that contains data • A storage deviceis the mechanical apparatus that records and retrieves data from a storage medium • Types of storage devices • Magnetic Storage • Optical Storage • Solid State Storage

16. Magnetic Storage • Stores data by magnetizing microscopic particles on the disk or tape surface • Contains a read-writehead • mechanism in the disk drive that reads and writes magnetized particles that represent data • Example • Hard Disk Drive [HDD] • Floppy Disk • Magnetic Tape

17. Magnetic Storage : HDD • Working of a hard disk • Hard disk platter - a flat, rigid disk made of aluminum or glass and coated with magnetic iron oxide particles • Harddisk- one or more platters and their associated read-write heads • Capacity up to 250 GB; Preferred type of main storage • Limitations • Headcrash- when a read-write head runs into a dust particle or other contaminant on the disk • Head crash damages some data on disk • Triggered by jarring the hard disk while in use • Not limited to hard disks Platter R/W Head

18. Optical Storage • Stores data as microscopic light spots (lands) and dark spots (pits) on the disk surface • Advantage • Less susceptible to environmentaldamage than data recorded on magnetic media • Example • CD [Capacity: 700 MB] • DVD [Capacity: 4.7 GB; Double Layered can store up to 8.5 GB] • Blue-Ray [Capacity: up to 50 GB]

19. Optical Storage : CD / DVD • Working of CD / DVD • Recordable technology uses a laser to change the color in a dye layer sandwiched beneath the clear plastic disk surface • Rewritable technology uses “phase change” technology to alter a crystal structure on the disk surface • Slower than hard disk • Not a suitable replacement for hard disk yet

20. Solid State Storage • Stores data in a non-volatile, erasable, low-power chip • Some solid state storage requires a device called a card readerto transfer data to or from a computer • Advantage • Provides faster access to data than magnetic or optical storage technology because it includes no moving parts • Portable • Example • USB flash drive • CompactFlash card

21. Moore’s Law:An Important Observation (-1-) • Moore's law describes a long-term trend in the history of computing hardware • Since the invention of the IC in 1958, the number of transistors that can be placed inexpensively on an IC has increased exponentially, doubling approximately every two years

22. Moore’s Law:An Important Observation (-2-)

23. References • Computer Concepts, by Parsons & Oja [Chapters 2] • http://en.wikipedia.org/wiki/ASCII • http://en.wikipedia.org/wiki/Moore's_law