©Brooks/Cole, 2003 Foundations of Computer Science from Data Manipulation to Theory of Computation Behrouz A. Forouzan, Brooks/Cole — Thomson Learning, Pacific Grove, USA, 2003.

©Brooks/Cole, 2003 Chapter 1 Introduction

©Brooks/Cole, 2003 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. After reading this chapter, the reader should be able to: O BJECTIVES Understand the sequential execution of statements in a program. Name the components of a computer: hardware, software, and data.

©Brooks/Cole, 2003 THE COMPUTER AS A BLOCK BOX THE COMPUTER AS A BLOCK BOX 1.1

©Brooks/Cole, 2003 Figure 1-1 Data processor model You can think of a computer as a data processor. Is it a specific-purpose machine or a general-purpose machine?

©Brooks/Cole, 2003 Figure 1-2 Programmable data processor model A program is a set of instructions that tells the computer what to do with data. A program is a set of instructions written in a computer language. The output data depend on the combination of two factors: the input data and the program.

©Brooks/Cole, 2003 Figure 1-3 Same program, different data

©Brooks/Cole, 2003 Figure 1-4 Same data, different programs

©Brooks/Cole, 2003 Figure 1-3 Same input data, same program When the same program is run with the same input, you expect the same output.

©Brooks/Cole, 2003 von NEUMANN MODEL MODEL 1.2

©Brooks/Cole, 2003 Figure 1-5 von Neumann model

©Brooks/Cole, 2003 Figure 1-5 von Neumann model: Four subsystems Memory Memory is the storage area Arithmetic logic unit (ALU) The ALU is where calculation and logical operations take place. Control unit The control unit controls the operations of the memory, ALU, and the input/output subsystem. Input/output The input subsystem accepts input data and the program from outside the computer. The output subsystem sends the result of processing to the outside.

©Brooks/Cole, 2003 Figure 1-5 von Neumann model Stored program concept: The von Neumann model states that the program must be stored in memory. The memory of modern computers hosts both a program and its corresponding data. They are stored as binary patterns (a sequence of 0s and 1s) in memory. Sequential execution of instructions A program is made of a finite number of instructions. They are executed sequentially.

©Brooks/Cole, 2003 COMPUTERHARDWARE See Chapter 5 COMPUTERHARDWARE 1.3

©Brooks/Cole, 2003 DATADATA 1.4

Figure 1-5 Storing data The von Neumann model does not define how data must be stored in a computer. A computer can store data in one of two states. You will learn how to store different types of data as a binary pattern, a sequence of 0s and 1s. Organizing data (data organization) Although data should be stored only in one form inside a computer, data outside a computer can take many forms. Data are organized into small units, small units are organized into larger units, and so on. Data

©Brooks/Cole, 2003 COMPUTERSOFTWARECOMPUTERSOFTWARE 1.5

Programs must be stored Programs are stored in computer memory. (see Figure 1-6) A sequence of instructions Programs must be a sequence of instructions. (see Figure 1-7) Why? Reusability. Programming

©Brooks/Cole, 2003 Figure 1-7 Program made of instructions

©Brooks/Cole, 2003 Algorithms A step-by-step solution to a program is called an algorithm. Languages A computer language has a more limited number of symbols and also a limited number of words. Software engineering The design and writing of programs in a structured form. Operating systems Computer Software

©Brooks/Cole, 2003 HISTORYHISTORY 1.6

Computer generation First generation: vacuum tubs Second generation: transistors Third generation: integrated circuit Fourth generation: micro-computers Fifth generation: multimedia History

©Brooks/Cole, 2003 Key Terms Algorithm Arithmetic logic unit (ALU) Black box Computer language Computer science Control unit Data processor Input data Instruction Integrated circuit Memory Microcomputer Operating system Output data Program Programmable data processor Software Software engineering Von Neumann model