Chapter 1 Introduction

OBJECTIVES After reading this chapter, the reader should be able to: Understand the concept of a black box, a data processor, and a programmable data processor. Define the von Neumann model and name its components: memory, arithmetic/logic unit, control unit, and input/output. Understand the stored program concept. Understand the sequential execution of statements in a program. Name the components of a computer: hardware, software, and data.

Definition A computer is a machine that manipulates data according to a list of instructions. Computer Science defines as “issues related to the computer”

1.1 THE COMPUTER AS A BLOCK BOX - Black box is a technical term for a device or system or object when it is viewed primarily in terms of its input and output characteristics. - Almost anything might occasionally be referred to as a black box: a transistor, an algorithm, humans, the Internet.

Figure 1-1 Data processor model - A computer acts as a black box that accepts input data, processes data and creates output - Problem : does not specify type of processing / operations

Programmable data processor model Figure 1-2 Programmable data processor model A program : is a set of instructions; what the computer should do Today’s understanding : a set of instructions written in a computer language Output data : consist of input and the program

Same program, different data Figure 1-3 Same program, different data

Same data, different programs Figure 1-4

1.2 VON NEUMANN MODEL(VNM)

VNM history The von Neumann architecture is a design model for a stored-program digital computer that uses a processing unit and a single separate storage structure to hold both instructions and data Its define how processing is done. Based on three ideas

Figure 1-5 von Neumann model

Idea 1: Four Subsystems for VNM Memory – is a storage area. Store programs & data during process ALU – calculation & logical operations take place Control Unit – controls the operations of the memory, ALU, IO subsystem IO – input; accepts input data/program from outside computer, output; sends the result of processing to the outside

Idea 2: Stored Program Concept The program must stored in the memory Stored in binary pattern : 1 or 0

Idea 3: Sequential Execution of instructions Made of a finite number of instructions CU fetches one instruction from memory, interprets it and execute

1.3 COMPUTER HARDWARE

Three broad categories Central Processing Unit Main Memory Input/Output

1.4 DATA

Storing data Store in two state : presence or absence Data such as text, image, audio, need to be changed to appropriate form (0s and 1s)

Organizing data Inside a computer, data should be stored only in binary pattern Outside a computer it may takes many forms Computers and the notation of data processing had created a study field known as data organization It’s to organize data into different entities and formats before storing them inside a computer.

1.5 COMPUTER SOFTWARE

Introduction Computer software : a collection of computer programs, procedures and documentation that perform some tasks on a computer system Programming : for these early computers meant changing the wiring systems or tuning on and off a set of switches.

Two aspect of programming to be understood. In VNM, the programs are stored in computer memory. Memory not only hold data, but also hold the program (Figure 1.6)

Programs Must Be Stored Figure 1-6 Programs Must Be Stored Program and data in memory

A Sequence Of Instructions Figure 1-7 A Sequence Of Instructions Program made of instructions; Why? For Reusability

Variety of Instructions Algorithm – step-by-step solution Language – to write computer instruction Software engineering – the design and writing of structured programs Operating systems – work as a manager to facilitate access of the computer components for a program

1.6 HISTORY

Mechanical Machines; Before 1930 Suanpan (the number represented on this abacus is 6,302,715,408) A mechanical calculator from 1914. Note the lever used to rotate the gears.

1801: punched card technology Punched card system of a music machine, also referred to as Book music, a one-stop European medium for organs Punched card with the extended alphabet

Charles Babbage, 1823 Babbage is credited with inventing the first mechanical computer that eventually led to more complex designs. Part of Babbage's difference engine, assembled after his death by Babbage's son, using parts found in his laboratory. The London Science Museum's replica Difference Engine, built from Babbage's design.

ENIAC (Electronic Numerical Integrator and Computer) was the first electronic general-purpose computer

1930s–1960s: desktop calculators The Curta calculator can also do multiplication and division

Advanced analog computers Cambridge differential analyzer, 1938

Early digital computers Punched tape programs would be much longer than the short fragment shown. Nine-track magnetic tape

Early Electronic Computers Special Purposes computer ;The Atanasoff–Berry Computer (ABC) was the first electronic digital computing device.

Program-controlled computers, general purposes machines A reproduction of Zuse's Z1 computer.

Colossus Colossus was used to break German ciphers during World War II.

Computers Based on The VNM EDVAC (Electronic Discrete Variable Automatic Computer) was one of the earliest electronic computers The EDVAC as installed in Building 328 at the Ballistics Research Laboratory.

COMPUTER GENERATIONS

FIRST GENERATION 1950-1959 Commercial computer Expensive Professionals Bulky, use vacuum tubes

SECOND GENERATION 1959-1965 Use transistor Use FORTRAN & COBOL

THIRD GENERATION 1965-1975 Use integrated circuit or microchip Minicomputer appeared on the market

Microchips (EPROM memory) with a transparent window, showing the integrated circuit inside Integrated circuit of Atmel Diopsis 740 System on Chip showing memory blocks, logic and input/output pads around the periphery

TV Typewriter 1969 Data General Nova.

FOURTH GENERATION 1975-1985 Microcomputer Emergence of computer network

FIFTH GENERATION 1985 – now Laptop & palmtop The use of multimedia + VR