CSE1301 Computer Programming: Lecture 1 Computer Systems Overview

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

Topics Hardware components Memory and Mass Storage I/O Devices Computer Networks, modems

Hardware Components of a Typical Computer Central Processing Unit (CPU) - performs the basic operations. Memory - holds algorithms and data. Input/Output (I/O) Devices - feed algorithm, data into memory; pass on results of the computer's activities. Input/Output Devices Central Processing Unit Memory

Features of Computers Speed: mips. Reliability. Memory –can store ~10 9 information items –can retrieve information in 75 nanoseconds (1 nanosec. = 10 9 sescs.). Cost: very low compared to human labour.

Transistor Gate: a group of transistors; –low -> 0, high -> 1 (digital quantities) Gates are the basic building blocks of computers. Base Collector Emitter

Types of Gates AND Gate OR Gate NOT Gate

Boolean Algebra AB AND Gate A AND B A OR B OR Gate

Boolean Algebra A 0 1 NOT A 1 0 NOT Gate

What is a "Chip"? Size: ~ 3 x 3mm. A chip consists of more than 100,000 transistors.

Memories Computers have to remember data. Registers: –store frequently used data; short term storage. Main memory: –stores less frequently used data; longer term storage.

What is a "bit"? Derived from BInary digiT 0 or 1 a BYTE = 8 bits a kilobyte = 2 10 bytes = 1024 bytes a megabyte = 1024 KB = 1,048,576 bytes a gigabyte = 1024 MB = 2 30 bytes

Main Memory Word = a fixed size chunk of bits which stores data –(e.g. 8, 16, 32 or 64 bits). Cells (word size): most of the memory. – (Slower, cheaper technology than registers) 10 6 cells < typical memory < 10 7 cells. –(e.g. 32 MB RAM: 32 megabytes of Random Access Memory) Each cell has a unique address.

Mass Storage The computer stores information for longer periods of time in FILES on mass storage. Cartridge. Hard drive. Floppy disk. Tape. Cassette. CD-ROM (Compact Disk Read-Only memory). Flopticals.

Input/Output Devices I/O Devices (Peripherals) are used to communicate with the outside world. Input Devices: –keyboard, mouse, microphone, optical reader for written text, sensors (camera, infra-red), punch-cards, "mark sense" cards. Output Devices: –video screen, text window, line printer, laser writers, effectors which operate machinery, audio speaker.

Other devices? Other computers - i.e. networking. Secondary storage –(devices for cheap storage of vast amounts of information). –eg. magnetic disk and tape

Uses of Computer Networks Electronic mail ( ). – address: –actually stored as: Electronic news –read monash.csse.cse1301 Access to remote machines –ftp: (File Transfer Protocol) –World Wide Web (www)

Uses of Computer Networks Shared databases. Share input/output devices. File servers.

CSE1301 Computer Network Network of IBM-compatible PCs. 32-bit machines (also 16-bit buses, software) Central file servers. Connected to other computers at Monash. On the Internet.

How do computers communicate? Computer networks transmit data in packets. The packets are sent via links from computer to computer. Each intermediate computer receives and retransmits the message.

Types of Computer Networks Local Area Networks (LAN) –Located close to each other. –Example: the PCs in the lab. Long Haul Networks –Separated by hundreds or thousands of miles. –Physical wires, telephone lines, satellites, etc.

Modes of communication Parallel communication: –all the bits are tranferred at the same time –each bit on a separate line Serial communication: –one bit at a time. 01

Modems ( MOdulator-DEModulator ) Monash Computer Modem Home Ccomputer Modem Digital Data Digital Data Audio signal phone lines

Modems ( MOdulator-DEModulator ) Digital data BUT phone lines send audio signals. speed of serial transmission: –bits per second (bps) common measure: –baud rate

Summary Computer = CPU + I/O devices + memory Transistors, gates, chips -> hardware. Main memory vs Mass Storage Computer communications: I/O devices, networks, modems Jargon and achronyms: demystification begun...

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