CSE1301 Computer Programming: Lecture 1 Computer Systems Overview Linda M c Iver

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

Algorithm Algorithm: A set of instructions describing how to do a task (or process). eureka! Programming: C

Topics Hardware components Computer Networks

Transistor Base Collector Emitter “semi-conductor” Binary digit or “bit”: 0  off 1  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

AB A 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 AB AND Gate A AND B 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: B = A AND B = 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/Output Devices Central Processing Unit Memory "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/Output Devices Central Processing Unit Memory

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/Output Devices Central Processing Unit Memory

"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 = 2 10 bytes a megabyte = 1024 KB = 2 20 bytes = 1,048,576 bytes a gigabyte = 1024 MB = 2 30 bytes a terabyte = 1024 GB = 2 40 bytes

I/O Devices (Peripherals) Input/Output Devices Central Processing Unit Memory 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 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

Modems ( MOdulator-DEModulator ) Remote Computer Modem Home Computer Modem Digital Data Digital Data 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 is –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): , 2.6, 3.5 6/e (2000): , 2.5, 3.5 Deitel&Deitel (3/e) 1.2 to to 1.17