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New Prac Times
• Remember to allocate yourself into pracs and tutes using allocate+ (there’s a link on the courseware page)
• New pracs have been opened (use allocate+ to select them if they suit you better) :– Monday 2-5pm– Thursday 2-5pm
AlgorithmAlgorithm: A set of instructions describing how to
do a task (or process).
eureka!
ProgrammingProgramming: C: C
Topics
• Hardware components
• Computer Networks
Transistor
Base
Collector
Emitter
“semi-conductor” Binary digit or “bit”:0 off1 on
Transistor
Base
Collector
Emitter
off : 0
Transistor
Base
Collector
Emitter
on : 1
Transistor
Base
Collector
Emitter
Modern-day “chips” (about 3 x 3 mm in size) can contain up to millions of transistors.
Gates
• Gate: a group of transistors
• Types:
AND Gate OR Gate NOT Gate
A AND B
A (0 or 1)
B (0 or 1)
(0 or 1)
1 AND 1
A (1)
B (1)
(1)
Example: AND Gate
1 AND 0
A (1)
B (0)
(0)
0 AND 1
A (0)
B (1)
(0)
Example: AND Gate
A B
0 0
0 1
1 0
1 1
A AND B
0
0
0
1A AND B
A
B
Example: AND Gate
A AND B
A (0 or 1)
B (0 or 1)
(0 or 1)
Gates and Boolean Algebra
A B
0 0
0 1
1 0
1 1
AND Gate
A AND B
0
0
0
1
0
1
1
1
A OR B
OR Gate
Gates and Boolean Algebra
A
0
1
NOT A
1
0
NOT Gate
Gates and Boolean Algebra
A =
A sequence of bits at a time:
1 1 0 0 1 1 0 1
B = 0 1 1 0 0 1 1 0
A AND B = 0 1 0 0 0 1 0 0
• Most PC’s do 32 bits at a time (“32-bit machines”), others as many as 128 bits at a time
• Gates are the basic building blocks of computers.
0 or 1
Hardware Components of a Typical Computer
Input/OutputDevices
Central Processing
UnitMemory
• "Buses" allow components to pass data to each other.
Hardware Components of a Typical Computer
• Central Processing Unit (CPU) - performs the basic operations.
• consists of two parts:– Arithmetic / Logic Unit (ALU) - data manipulation
– Control Unit - coordinate machine’s activities
Input/OutputDevices
Central Processing
UnitMemory
Main Memory
• Holds programs and data• Stores bits in fixed-sized chunks:
– “word” (8, 16, 32, or 64 bits)• Each word is stored in a cell, which has a unique
address• Cells can be accessed in any order • Thus, random-access memory or “RAM”
Input/OutputDevices
Central Processing
UnitMemory
"Bits, Bytes, Kilo-, Mega-, Giga-, …"
• A bit: 0 or 1• A word: chunk of bits (8, 16, 32 or 64 bits)
• a byte = 8 bits
• a kilobyte = 1024 bytes = 210 bytes
• a megabyte = 1024 KB = 220 bytes = 1,048,576 bytes
• a gigabyte = 1024 MB = 230 bytes
• a terabyte = 1024 GB = 240 bytes
I/O Devices (Peripherals)
Input/OutputDevices
Central Processing
UnitMemory
• I/O Devices (Peripherals) - to communicate with the outside world.
• Examples: – Input: keyboard, mouse, microphone, scanner,
sensors (camera, infra-red), punch-cards, "mark sense" cards.
– Output: video, printer, audio speakers, etc.
Other Input/Output Devices
• Long term storage: files in secondary (mass) storage devices.– Examples: Hard drive, Floppy disk, Tape,
Cassette, CD-ROM (Compact Disk Read-Only Memory), Flopticals, Cartridges, etc.
• Communications devices– Examples: Modems, Ethernet cards
Speed
CPU clock speed: cycles per second ("hertz")– Pentium 4 1.8 GHz, 733 MHz G4
• BUT different CPU designs do different amounts of work in one clock cycle
– “flops” (floating-point operations per second)– “mips” (million instructions per second)– other benchmarks
Speed (continued)
• System clock/bus speed• communication between CPU, memory and I/O devices
• depends on main board (a.k.a. "motherboard") design
– 50MHz, 60MHz, 66MHz, 100Mhz, 133MHz, ++
– Intel 1.50GHz Pentium-4: 400MHz bus speed
• In common PC's:– system clock speed can be set in the main board
– CPU clock speed is the bus speed times a "multiplier"
» Example: A 150MHz CPU may be running at 2.5 x 60MHz, 3 x 50MHz or 2 x 75Mhz ("overclocked" system bus)
Speed (continued)
• RAM access speed• about 60ns (1 nanosecond = a billionth of a
second), and getting faster• may be rated with respect to "bus speed" (eg. PC-
100)
• Cache memory• faster than main memory (about 20ns access
speed), but more expensive• contains only data which the CPU is likely to use
next
Speed (continued)
• I/O device speed• Mass storage access
» 3.5in 1.4MB floppy disk: about 500kb/sec at 300 rpm (revolutions per minute)
» 3.5in hard disk: average seek time about 8.5 microsecond, and 7,200 rpm
• Communications– Examples: modems at about 56 kilobits per second,
and network cards at 10 or 100 megabits per second.
• Interface– Examples: ISA, PCI, IDE, SCSI, ATA, USB, etc....
Reliability
• Maintenance issues
• Operating conditions• Example: heat, ventilation, "over-clocking,” power
supply
• Error detection• Example: parity check, CRC
Note: Most system failures are due to software (i.e. programming) flaws rather than hardware
Modes of communication
• Parallel communication: – all the bits are transferred at the same time – each bit on a separate line
01
• Serial communication: – one bit at a time.
1
001
Modems (MOdulator-DEModulator)
Remote Computer
ModemHome
Computer
ModemDigitalData
DigitalData
Audio signal (analog)phone lines
Computer Networks
• Types– Local Area Networks (LAN)
• Computers in an organization.
• Example: the PCs in the lab.
– Long Haul Networks • Separated by hundreds or thousands of miles.
• Physical wires, telephone lines, satellites, etc.
• Example: Internet “backbone”
Computer Networks
• Method of communication– Each computer has an address
• IP address of www.monash.edu.au is 130.194.11.4
– A sender computer transmits data through the network in packets
– Each packet is tagged with the destination and return address
• Data too big for one packet is split into several packets, labelled in sequence
Computer Networks
• Method of communication (continued)
– Packets are sent via links from computer to computer (“routing”)
– Each intermediate computer receives and retransmits the message (“hops”)
• Packets may not arrive in the order in which they were sent.
– The recipient computer puts the packets in correct sequence and retrieves the data
Summary
• Transistors, gates, chips, hardware.
• Computer = CPU + Memory + I/O Devices
• Networks, modems
• Jargons and acronyms
Further Reading
Brookshear:
• 4/e (1994): 1.1, 1.2, 2.6, 3.8
• 5/e (1997): 1.1 - 1.3, 2.6, 3.5
• 6/e (2000): 1.1 - 1.3, 2.5, 3.5
Deitel&Deitel (3/e)
• 1.2 to 1.5
• 1.15 to 1.17
