1. McGraw-Hill Technology Education
Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.

2. Transforming Data Into Information
Chapter 5A
Transforming Data Into Information

3. How Computers Represent Data
Number systems
A manner of counting
Several different number systems exist
Decimal number system
Used by humans to count
Contains ten distinct digits
Digits combine to make larger numbers

4. How Computers Represent Data
Binary number system
Used by computers to count
Two distinct digits, 0 and 1
0 and 1 combine to make numbers
Teaching Tip
Table 5A.1 on page 187 provides the first 17 binary numbers and their decimal equivalent. A fun exercise is to teach the students to count in binary on their fingers.

5. How Computers Represent Data
Bits and bytes
Binary numbers are made of bits
Bit represents a switch
A byte is 8 bits
A nibble is 4 bits
Byte represents one character

6. How Computers Represent Data
Text codes
Converts letters into binary
Standard codes necessary for data transfer
EBCDIC (Extended Binary Coded Decimal Interchange Code) – 8-bit code, used in IBM mainframe and midrange, rarely used in PC
ASCII (American Standard Code for Information Interchange) – 8-bit code,
Characters for values from
Extended ASCII – 8-bit code
Characters for values from
Unicode, provides up to 4 bytes (32 bits),
Can represent 4 billion characters. All languages on the planet
Insider information
Windows XP, Mac OS X and newer flavors of Linux are fully Unicode compatible.

7. How Computers Process Data
The CPU
Central Processing Unit
Brain of the computer
Two basic parts
Control unit (CU)
Controls resources in computer
Instruction set (list of all operations that the CPU can perform), expressed in “microcode” (a series of basic directions that tell the CPU how to execute more complex operations)
Arithmetic logic unit (ALU)
Arithmetic operations (+, -, *, /)
Logical operations ( =, >, <)
Includes a group of Registers (high-speed memory locations built directly into the CPU, used to hold the data currently being processed).
Teaching tip
Table 5A.4 on page 190 lists the operations handled by the common ALU.

8. How Computers Process Data
Machine cycles
Steps by CPU to process data
Can be broken down into two smaller cycles
Instruction cycle (CPU takes two steps)
Fetching. CU retrieve a command or data from memory
Decoding. CU breaks down (decode) the command into instructions that corresponds to those in CPU’s instruction set
Execution cycle (CPU takes two steps)
Executing. CPU carries out the instructions in order by converting them into microcode.
Storing. CPU may be required to store the results in memory.
CPU performance can be measured in MIPS or BIPS
Pipelining processes more data (up to 20 instructions)
Multitasking allows multiple instructions
(threading or hyperthreading)
Insider information
More pipelines mean a faster and more efficient CPU. The current fastest CPU on the market, the Apple G5 has 80 pipelines!

9. How Computers Process Data
Memory
Stores open programs and data
Small chips on the motherboard
More memory makes a computer faster
Volatile or non-volatile

10. How Computers Process Data
Nonvolatile memory
Holds data when power is off (also called “burning in the data”, usually done in factory)
Read Only Memory (ROM) or
Programmable ROM (PROM) (one-time PROM)
Erasable Programmable ROM (EPROM)
Erased by exposing it to strong ultraviolet light from a mercury-vapor light source
Electrically Erasable Programmable ROM (EEPROM)
erased and reprogrammed repeatedly through the application of higher than normal electrical voltage
Basic Input Output System (BIOS)
Power On Self Test (POST)
Flash memory
Special form of nonvolatile memory
Camera cards, USB key chains
Teaching tip
If you are in a computer lab, spend a few minutes exploring your BIOS. Demonstrate what happens when values are adjusted. Walk through a POST check. Unplug a device and generate POST errors. Be sure to reset everything before moving on with the lecture!

11. How Computers Process Data
Volatile memory
Requires power to hold data
Random Access Memory (RAM)
Data in RAM has an address
CPU reads data using the address
CPU can read any address
Single in-line memory modules (SIMMs)
contacts on a SIMM are redundant on both sides of the module
32-bit data path
Dual in-line memory modules (DIMMs) found in desktop computers
have separate electrical contacts on each side of the module
64-bit data path
Small outline DIMM (SO-DIMM) in laptops
Teaching tip
One of the most commonly asked questions is “How do I speed up my computer”. The simplest answer is to add RAM. The Productivity Tip on page 200 provides some guidelines when to add RAM.

12. How Computers Process Data
Volatile memory
SRAM (Static RAM)
Does not need to be periodically refreshed, because of bistable latching circuitry
DRAM (Dynamic RAM)
need to be periodically refreshed, because it stores each bit of data in a separate capacitor within an IC. Since real capacitors leak charge, the information eventually fades unless the capacitor charge is refreshed periodically.
has asynchronous interface: means that it responds as quickly as possible to changes in control inputs
Teaching tip
One of the most commonly asked questions is “How do I speed up my computer”. The simplest answer is to add RAM. The Productivity Tip on page 200 provides some guidelines when to add RAM.

13. How Computers Process Data
SDRAM (Synchronous dynamic RAM) OR
SDR SDRAM (single data rate SDRAM)
has synchronous interface, means it waits for a clock signal before responding to control inputs and is therefore synchronized with computer inputs.
accepts one command and transfer one word of data per clock cycle
DDR SDRAM (double data rate SDRAM)
makes higher transfer rates possible by more strict control of the timing of the electrical data and clock signals.
The interface uses double pumping (transferring data on both the rising and falling edges of the clock signal.
MDDR SDRAM (Mobile DDR SDRAM)
Used in mobile phones, handhelds and digital audio players

14. Affecting Processing Speed
Cache memory
Very fast memory
Holds common or recently used data
Speeds up computer processing
Most computers have several caches
L1 holds recently used data
CPU-resident cache, 256 KB built-in
L2 holds upcoming data
may or may not be CPU resident, 512 KB, 1 MB or 2 MB
L3 holds possible upcoming data
motherboard-resident cache

15. Memory Hierarchy Memory hierarchy in most computers is:
Processor registers – fastest possible access (usually 1 CPU cycle), only hundreds of bytes in size
Level 1 (L1) cache – often accessed in just a few cycles, usually tens of kilobytes
Level 2 (L2) cache – higher latency than L1 by 2× to 10×, often 512 KB or more
Level 3 (L3) cache – higher latency than L2, often 2048 KB or more
Main memory – may take hundreds of cycles, but can be multiple gigabytes.
Disk storage – millions of cycles latency if not cached, but very large
Tertiary storage – several seconds latency, can be huge

16. Components affecting Speed

17. Affecting Processing Speed
Registers
Number of bits processor can handle
Word size (size of the register) or (the amount of data with which the computer can work at any given time)
Larger indicates more powerful computer
Increase by purchasing new CPU
32-bit processor , 64-bit processor

18. Affecting Processing Speed
Virtual RAM (Virtual Memory)
Computer is out of actual RAM
File that emulates RAM
Computer swaps data to virtual RAM
Least recently used data is moved
Swap out
Swap in

19. Affecting Processing Speed
The computer’s internal clock (System clock)
Like modern wristwatches, clock is driven by quartz crystal.
When electricity is applied, the molecules in the crystal vibrates millions of times per second, a rate that never changes.
Speed of the vibrations is determined by the thickness of the crystal.
Computer uses the vibrations of the quartz in the system clock to time its processing operations.
Hertz (Hz) is the measure of cycles per second, MHz, GHz, etc.
Teaching tip
Spend a little time here discussing over clocking. Over clocking causes the computer to run faster than designed. Possibly, you have students that can share stories of over clocking.

20. Affecting Processing Speed
The computer’s internal clock (System clock)
Computer’s operating speed is tied up to the speed of the system clock.
For example, if a computer’s clock speed is 800 MHz, it “ticks” 800 million time per second.
A clock cycle is a single tick.
A processor can execute an instruction in a given number of clock cycles.
As the system’s clock speed increases, so does the number of instructions it can carry out each second.
1GHz, 3 GHz processor, etc.
Teaching tip
Spend a little time here discussing over clocking. Over clocking causes the computer to run faster than designed. Possibly, you have students that can share stories of over clocking.

21. Affecting Processing Speed
The bus (a group of parallel wires)
Electronic pathway between components
Number of wires affects in a bus affects speed at which data can travel between hardware components
Each wire can transfer one bit of data at a time, so eight-wire bus can move eight bits at a time. Similarly, 16-bit bus, 32-bit, and 64-bit bus (also called FrontSide Bus).
Two main buses in a computer:
The Internal bus (system bus)
Resides on the motherboard and connects the CPU to other devices that reside on the motherboard.
Has two parts: 1) Data bus 2) Address bus
The External bus (expansion bus)
Connects external devices, such as keyboard, mouse, modem, printer, etc, with the CPU.

22. Affecting Processing Speed
Data Bus
Connects the CPU, memory, and other hardware devices on the motherboard.
Like the processor, the bus’s speed is measured in megahertz (MHz), because it has its own clock speed.
Today’s PCs have a bus speed of either 100 MHz or 133 MHz, or 800 MHz (common)
Bus speed is directly tied into the CPU speed.
Consider a system bus that runs at 400 MHz supporting a 1.6 GHz processor. Explain……..
Address Bus
Connects only the CPU and RAM

23. Affecting Processing Speed
External bus standards
Industry Standard Architecture (ISA)
16-bit data bus
Local bus
Is an Internal Systems bus that runs between components on the motherboard, developed to attach faster devices to the CPU.
Peripheral control interface (PCI) bus
Type of local bus designed by Intel to make it easier to integrate new data types, such a audio, video and graphics.
Universal serial bus (USB)
Unlike PCI, USB is a hot swappable bus, means it can be connected and then disconnected without affecting machine.
IEEE 1394 (FireWire)
Used to connect video devices.
PC Card (for Laptop computers)

24. Affecting Processing Speed
Accelerated Graphics Port (AGP) bus
Connects video card to motherboard
Special architecture that allows the video card to access the system’s RAM directly
Extremely fast bus
Found in all modern computers

25. Chapter 5A
End of Chapter