forth edition

Introduction

Turing Model

what computer model can be described?

  • a basic data processor
    • input data
    • computer
    • output data

basic data process can only handle specific computation, we need genneral model

  • a general data processor (a programmable data processor)
    • input data
    • computer
    • a program, a set of instructions that tells computer what to do with data
    • output data

This is turing model. It can do same thing with modern computer, if it has same input and same program

Number System

Introduction

A number system defines how a nubmer can be rrepresented using distinct symbols.

Positional Number System

The postion a symbol occupies in the number determines the value it represents

NoPositional Number System

Still uses a limited number of symbols in which number of symbols in which each symbol has a value. However, the position a symbol occupies in the number normally bears no relation ot its value.

Data Storage

As discussed before, a computer is a programmable data processing machine. Before
we can talk about processing data, we need to understand the nature of data.

Data Types

Data today come in different forms including numbers, text, audio, images, and video

Data inside the computer

All data types are transformed into a uniform representation when they are stored in a
computer and transformed back to their original form when retrieved. This universal
representation is called a bit pattern

Bits

A bit represents the state of a device that can take one of two states.
For example, a switch can be on or off.

Bit patterns

To represent different types of data, we use a bit pattern, a sequence, or as it is
sometimes called, a string of bits.

Operating Systems

Introduction

Evolution

Components

A modern operating system has at least four duties: memory manager, process manager, device manager, and file manager.

Like many organizations that have a department that is not necessarily under any specific manager, an operating system also has such a component,

which is usually called a user interface or a shell. The user interface is responsible for communication outside the operating system.

A Survey of Operating Systems