1 The development of modern computer systems Early electronic computers Mainframes Time sharing Microcomputers Networked computing

2 Early electronic computers ENIAC (1946) - Electronic Numerical Integrator and Calculator –First general purpose purely electronic digital computer. –Built for US Army to make calculations for weather predictions & ballistics tables. –18, 000 vacuum tubes, space 50 X 30 ft, weighed 30 tons. –Numbers are entered by manually setting its 6000 switches.

3 Early electronic computers (cont.) EDVAC - Electronic Discrete Variable Calculator –A general instruction set and a stored program. –Both numbers and program instructions were stored electronically in the computer’s memory. UNIVAC - Universal Automatic Computer –First commercially built computer. –Delivered to the U.S. Census Bureau in 1951 to tabulate the results of the previous year’s census.

4 Early electronic computers (cont.) John von Neumann ( ) –“von Neumann machine”. –Binary number computation. –Memory for data storage. –Input and output devices. –Overall logical control.

5 Mainframes Generation –The development of modern computers is often described in terms of the “generation”, in which a particular technology was used. Architecture –The overall design of a computer’s electronic circuitry and its logical functionality is called its architecture.

6 Mainframes (cont.) First generation – 1950s –Architecture Electronic circuitry: vacuum tubes. Memory: magnetic cores. –Stored program Program: machine language. Processing: a single program at a time. –Peripheral devices Input and output: punched cards. Data storage: magnetic tapes.

7 Mainframes (cont.) Second and third generations – 1960s –Architecture Electronic circuitry: transistors to integrated circuits (ICs). –Symbolic languages Assembly language. FORTRAN - FORmula TRANslation, first high- level language. COBOL - Common Business-Oriented Language. LISP - LISt Processing.

8 Mainframes (cont.) –Translators: translating high-level language to machine-understandable form Assemblers: converting program instructions from assembly languages into the machine language. Compilers: translating program statements from FORTRAN and COBOL to machine language. Interpreter: translating and executing each program statement dynamically.

9 Mainframes (cont.) –Operating Systems (OS): a program to control the overall processing of the machine Batch processing: jobs that were similar in their requirements were grouped together into batches and run sequentially. JCL (Job Control Language): to minimize operator intervention, JCL cards were inserted between the card decks of each job to direct how each job was to be processed. Mass storage: disk drives provided permanent storage and fast access to large quantities of data.

10 Time sharing Time sharing controls computer operations in such a way that input and output activity (I/O) would not slow down the primary computation. Multiprocessing (mid-1960s) –A program was broken into tasks (processes). –Each process was allow a interval of time for execution before control was passed to another one. Interactive computing (early 1970s) –User could sit at a remote terminal and communicate directly with the computer. –Allow multiple users at the same time.

11 Microcomputers Fourth generation – 1970s –Chip circuitry: VLSI - Very Large Scale Integration, which could contain all logic circuits on a single chip. These chips were known as microprocessors. Minicomputers – 1970s –Lower cost and more accessible computing power. –Architecture is based on the 16-bits (vs. the 32-bits in use for larger computers) representation of data in computer memory.

12 Microcomputers (cont.) PC - Personal Computer – 1970s-1980s –Low cost computers intended for personal use. Input: keyboard. Output: screen. Data storage: removable floppy disks. Examples: Apple, IBM PC. –DOS - Disk Operation System DOS was developed by Microsoft for the IBM PC. DOS provides the basic functions for a single user to handle data storage and to control input and output devices and program execution.

13 Microcomputers (cont.) –GUI – Graphical User Interface With the introduction of the Mac (Macintosh) computer by Apple in Information was presented to the user via pictures, known as icons. A new hand-held input device, called a mouse, was available for selecting choices from the screen. Mac utilized a bit-mapped display which is able to display both graphics and text. Each graphical image is composed of small dots called pixels which must be manipulated individually by the computer ‘s programs.

14 Microcomputers (cont.) PC software –Software are programs directing a computer’s operations and solving problems. –Hardware are the physical devices that form the computer itself. –The popularity of PCs grew rapidly in the 1980s as innovative application programs were developed to enable nontechnical users to do useful tasks on the computer.

15 Microcomputers (cont.) Word processors allow a user to write and edit text. Spreadsheet programs provider convenient computational power for data stored in tables. Business graphics programs are able to display data in the form of graphs and charts.

16 Microcomputers (cont.) Workstations – 1980s –For complex number crunching scientific and engineering programs. –For a single user. –Using multiprocessing systems. –Well suited for networking use.

17 Networked Computing Computer networks – 1980s-present –Users access computers which are at a distance. –Users share data. –Users transmit messages between computers. Telephone lines –An electronic device called a modem allows computers to transmit data over telephone lines,

18 Networked Computing LAN – Local Area Network –A LAN allows computers in reasonable proximity of each other to be connected by cabling over which data can be transmitted from one machine to another without the use of telephone lines. Distributed computing –Techniques of shared processing over networks are generally called distributed computing. –A computer that provides the core of the services is called a server. –Any computer requesting a service is known as a client.