1. Distributed Information Systems - The Client server model Week 1 – Lecture 2

3. Operating system Proc A Proc B Proc C Operating system Proc X Proc Y Proc Z Client process Client process Server process Server process Host 1 Host 2 Proc. A asks Proc. X to Perform a service. Proc. Z asks Proc. C to Perform a service Host 1 does not ask Host 2 to perform a Service

4. A brief history of IS 1970’s 1980’s 1990’s 2000’s Main frame or mini with dumb terminals LAN server & PC s 2 tier Client Server 3 & 4 tier Client server

6. Network Dumb terminals Centralised Mainframe or Minicomputer Basic presentation Form definition Application Database File system

8. Network PCs PC Lan PC Server File system Presentation Application Database

9. Network PCs PC Lan File Server Operating system Application Operating system File system

11. Network PCs 2 Tier Client server Database Server PC or UNIX Database File system Presentation Application

12. Network PCs 2 Tier Client server Database Server Windows or UNIX Proc C Operating system File system Operating system Application Database

14. Network PCs Servers Database File system Presentation 3 Tier Client/Server Application

15. Network PCs 3 Tier Client/Server Proc C Operating system File system Operating system Presentation Process Database Process Proc C Operating system Application Process

17. Network PCs Servers Database File system Browser 4 Tier Client/Server Application Web

18. Network PCs 4 Tier Client/Server Proc C Operating system Browser Process Proc C Operating system Application Process Operating system File system Database Process Operating system WEB Server