四川大学计算机导论期末复习资料总结。

1． Numbers Convertion

In this section, you will convert numbers among binary, decimal and hexadecimal representations.

a. Complete the following chart by converting the numbers given in one of the notations to the

other two. Show calculations.

b. What is the minimum number of bits that can be used to represent the

decimal number 1013? (Hint: convert 1013 to binary.)

10

c. What is a purpose of using hexadecimal notation?

Answer:

Using hexadecimal notation is to express binary values more concisely.

Because when we express a value, it will take more digits in binary

notation than in decimal notation.

d. What is ASCII code?

Answer:

ASCII code is American Standard Code for Information Interchange. It

is the built-in binary code for representing characters in all computers

except IBM mainframes and realizes data transmission standardization

in vary computer systems. In modern time most mainframe and all PC

use it . ASCII code includes two set : Standard ASCII code with 128

characters and Extended ASCII code with 128 characters appended.

2. Computer Speed

a. One Hz is one _____ per _____.

四川大学计算机导论期末复习资料总结。

One Hz is one cycle per second.

b. Define IPS.

IPS is instructions per second which is a rating of how many instructions can be executed by

a processor in a given second.

c. Answer the following questions on the relationship of Hz to IPS.

i. Which is a better determiner of speed: MHz or IPS?

IPS is a better determiner of computer performance.

ii. Does a high Hz equal a high IPS, and can they be inversely proportional? Explain.

A high Hz can indicate that the IPS is high, but they are not directly proportional, but can

never be inversely proportional

iii. How is it possible for a machine with a lower clock speed (Hz) to have a higher

IPS than a machine with a higher clock speed?

An instruction can take a variable amount of cycles or partial cycles. Thus, a computer can

execute instructions more quickly than another computer because of this.

d. What is the relationship between the system clock and Hz?

The system clock sends out pulses at regular intervals to set up the timings for all timed

system activities, such as determining the Hz of a processor.

3. BIOS and CMOS

a. Explain the function of the BIOS ROM in the boot process.

The BIOS ROM is a permanent storage device that contains the startup instructions

for the computer.

b. Define flashing, with respect to BIOS ROM.

Flashing is the process of rewriting an EEPROM. This process allows the BIOS to be

updated without changing ROM chips.

c. Explain the function of the CMOS in the boot process.

The CMOS contains the configurable system information that the BIOS reads during

startup.

d. What is the advantage of having an unchangeable ROM and a changeable CMOS

during the boot process?

By having an unchangeable BIOS, a default startup configuration is always possible.

Since, however, startup configurations may differ from machine to machine, the

changeable CMOS allows users to specify exactly how the boot will occur on their

machines, possibly changing the startup from the default.

四川大学计算机导论期末复习资料总结。

4. Layers e. Consider that the CMOS has lost power. i. What happens to the data that was stored in the CMOS? The CMOS is volatile and will lose all data contained in it if it loses power ii. How does the CMOS losing power affect the boot process? When CMOS power fails it no longer contains configuration data, and therefore when a machine is booted, it will use the default settings contained in the BIOS. f. List two ways to change the information in the CMOS. Windows Plug-N-Play, as an example. BIOS setup and configuration utility, as an example.

a. The layers of software have already been list down. Fill the correct number of

layers in table from lowest to highest.

(1) User Interface

(2) Run-Time Libraries

(3) User-Written Scripts or Macros

(4) Application Programming Interface

(5) Kernel

(6) BIOS

(7) Application

(8) Operating System

(9) Device Drivers

b. Describe encapsulation with respect to the layers of software.

四川大学计算机导论期末复习资料总结。

Encapsulation means that a layer is closed off from other layers, achieving only it

owns ends without knowing much about the other layers.

c. Describe abstraction with respect to the layers of software.

Abstraction is the means of sharing data and communicating that is established

between various layers of software.

d. What advantage do encapsulation and abstraction give to software developers?

Encapsulation and abstraction allow developers to provide limited means of

accessing data to their layer, and that they only must support limited influx of data

from other layers' abstraction. The layer can be comprised of code that other layers

need not be involved in.

5. Networks

a. What is a LAN?

Local Area Network. A network smaller than a WAN; typically a computer network

covering a local area, like a home, office, or group of buildings.

b. What is a WAN?

Wide Area Network. A computer network larger than a LAN; typically a network that spans

buildings, cities, or countries. The internet is a WAN.

c. What is a thin client?

A network application in which the client does very little processing and the network server

does most of the work.

d. What is a thick client?

A network application in which the client does relatively significant processing, and the

network server does more simple tasks.

e. What are the implications of thin and thick clients for a server?

Thin clients make larger processing demands on a server, and so the server can support fewer

thin clients.

f. What is a domain name?

A fully-qualified domain name contains a machine, domain, and top-level domain

designation. From this common name structure an IP address can be referenced and the

machine connected to.

g. Explain what is indicated by each part of http://.

www is the actual name of the machine (server) from which the data is being

requested.

四川大学计算机导论期末复习资料总结。

icarnegie is the domain in which the machine www resides. This domain may contain

many machines.

com is referred to as a top-level domain. Many domains are housed under the umbrella of org.

This is one of the many top-level domains and allows greater variation in naming.

h. List five non-country, top-level domains.

.com, .mil, .gov, .int, .net

6. Data Integrity

a. In the context of Java applets, what is a sandbox, and how does it protect computer information?

A sandbox is a secure location to run Java applets and ActiveX controls.

A sandbox protects the data on your computer from outsiders, who can use Java

applets and ActiveX controls to access secure or private information.

b. What is a digital certificate, and how does it protect computer information?

A digital certificate is a method of authentication for identifying the author of a given

software program.

A digital certificate allows the user to ensure that the software being downloaded is

from a reputable source before running it.

c. What is a firewall, and how does it protect computer information?

A firewall is a set of rules that govern communications over a network. A firewall

basically denies communications unless a rule allows them to occur.

A firewall protects a computer system, by always denying network communications

requests that the user has not predefined as permissible.

d. In the context of a Web browser, what is a cookie, and how might it not protect computer

information?

A cookie is a text file that contains information about visiting Web sites.

Cookies are thought not to protect a person's privacy by allowing Web sites to read

them and determine usage patterns of Web sites and pages visited.

7. Dictionary-based Compression

Consider the message below:

exam1, exam2, and exam3 are required exams.

a. How many bytes does the message contain (each character is 1 byte

including spaces)?

四川大学计算机导论期末复习资料总结。

b.

c.

d.

e. Create a compression dictionary and calculate its size in bytes. What is the compressed message? How many bytes did the entire compression use? Show calculations. Is dictionary-based compression a lossy compression? Explain.

43 bytes

$exam 5 bytes

$1, $2, and $3 are required $s.

31 bytes (message) + 5 bytes (dictionary) = 36 bytes.

No, dictionary compression is not a lossy compression because data is being replaced with

shortened representations and not lost.

8． Port Identification

Consider the following devices:

Mouse Printer Keyboard Modem Speaker Digital

camera Ethernet jack Monitor

For the following questions, indicate which device(s) should be plugged in

which port(s) A-H shown in the diagram below.

a. What device(s) can be plugged into port A?

i. What is the name of this port?

ii. Is this a serial port or parallel port?

b. What device(s) can be plugged into port B?

i. What is the name of this port?

ii. Is this a serial port or parallel port?

c. What device(s) can be plugged into port C?

i. What is the name of this port?

ii. Is this a serial port or parallel port?

d. What device(s) can be plugged into port D?

四川大学计算机导论期末复习资料总结。

e.

f.

g.

h. i. What is the name of this port? ii. Is this a serial port or parallel port? What device(s) can be plugged into port E? What device(s) can be plugged into port F? What device(s) can be plugged into port G? What device(s) can be plugged into port H?

Keyboard or mouse.

PS/2 port

Serial

Digital camera, keyboard, mouse, printer, external storage, network adapter, etc.

USB port

Serial

Modem or mouse

DB-9 (serial) port

Serial

Printer

Parallel (printer) port

Parallel

Speaker

Monitor

Phone line

Ethernet network

9． Computer Configuration

Let us assume that you are purchasing a new computer for a specific usage. You

need to choose a computer from various available configurations.

Listed below are four different usage cases of a computer (a-d). For each usage

case, identify components of the computer configuration that are most

important to consider. Explain your answers.

Components to be considered include (but are not limited to):

Monitor size/resolution Graphics card/video card Storage devices (e.g. DVD-ROM) Memory (RAM, cache, and hard disk) Disk controller interfaces (ATA, EIDE)

For example, if a computer were to be used for viewing movies, a DVD-ROM

drive is needed since movies are available as CDs and now increasingly as DVDs.

A large monitor (about 19”) that supports high resolutions and a video card will

also be necessary to enjoy the movie.

四川大学计算机导论期末复习资料总结。

a. Playing three-dimensional arcade games ？

b. Server machine to store and retrieve huge volumes of data？

a. Simultaneously running a number of programs

To run a number of programs simultaneously, a configuration with sufficient RAM must be

selected so that the performance would not suffer because several large programs might be

running concurrently.

b. Running a speed-critical application

For a speed-critical application, a configuration with a fast processor is essential. In addition

to a fast processor, a proper memory hierarchy is needed so as to take advantage of the fast

processor. Also to be taken into account are L1 and L2 cache memories, as well as the amount of

main memory. Typically, it is preferable to have L1 and L2 cache memories that use SRAM, and a

main memory that uses SDRAM.

c. Storing and retrieving huge volumes of data

To store huge volumes of data, a hard disk with a huge capacity is needed. If frequent

retrieval of data is needed, then fast access times are needed. It would be advantageous if direct

memory access were used to transfer data from the hard disk to the RAM without wasting

processor time. Thus a hard disk drive with an Ultra ATA controller and DMA data transfer would

be preferred.

d. Purchasing a basic configuration, to be upgraded later as needed

To have room for further upgrades and additions, it is essential to ensure that the computer to

be purchased has sufficient expansion options. The numbers of free internal and external bays

available are to be considered, as well as the number of built-in ports that are available. If the

initial purchase only has a keyboard and mouse for input and a monitor for output, it is essential to

ensure that ports are available for further additions such as printers, scanners, modems, external

hard drive, etc.

10. Software Licenses

I． Define shrink-wrap license.

II． Define shareware license.

III． Define public-domain license.

IV． For each type of license listed in parts a, b, and c, give one example of

a program distributed under that type of license.

A licensing agreement that is printed on a software package that is automatically agreed to

when the user opens the software. While this is not always the case nowadays, the term mainly

refers to software that is purchased before use.

Shareware licenses grant the user permission to try the software before it is bought. Users

need to send in a registration fee if they wish to continue to use it.

This type of license allows the user to modify, append to, and manipulate the software in any

way. The software "belongs to the people."

Shrink-wrap: Microsoft Windows Me, as an example.

Shareware: WinZip, as an example.

Public Domain: Apache Web Server, as an example.

四川大学计算机导论期末复习资料总结。

11. Data Transfer

a.

b.

c.

d. What is the purpose of an NIC? What is the function of a hub? What is the function of a router? Describe how a website request given the URL is made from a home

computer to the Internet once it reaches the DNS server?

e. To ensure data transmitted is correct, even parity bit protocol is used. Fill

in the parity bits for the following data:

The purpose of a Network Interface Card (NIC) is to connect the computer to a network,

allowing the system to send and receive data over the network connection.

A hub is used to connect machines in a star topology network. It sends data that it receives

back to every port, so that the data is can be sent to the correct system.

A router is a computer that maintains a table of ports and addresses, matching ports with one

or many given addresses. A router sends packets that it receives only to the port that the packet's

destination address matches, using the table to translate the address to the correct port.

When the URL data reaches the DNS server, the DNS server looks into the database to find

the destination IP address corresponding to the domain name of the host. After the IP address is

determined, the data passes through the router, which decides the path to send the data to the

destination IP address. The data packets may go through many routers before arriving at the

12. Computer System Attacks

四川大学计算机导论期末复习资料总结。

a. Describe each of the following computer system attacks

i.

ii.

iii.

iv. file virus macro virus Trojan horse worm

b. Name two software programs that protect against the attacks listed in

part a.

A virus hidden in an application program. When the program is executed, the virus replicates

itself and can perform malicious activities now or later.

A virus hidden in a document type that supports macros or scripts, such as Word or Excel.

Opening the document can cause the macro to execute immediately.

A computer program that appears to perform one function while actually performing another.

A program that gains access to a computer, typically through a network security flaw, or

another opening caused by careless system administration. The worm then attempts to access

additional computer systems. It may have a payload or simply clog up the computer.

Norton Anti-Virus and Macaffee VirusScan, as examples.

13． Component Identification

Choose among the following components to label the image:

Motherboard

Power supply

BIOS ROM Chip

Cooling fan

Expansion slot

RAM chip

Expansion card

Disk drives

Chipset

四川大学计算机导论期末复习资料总结。

IDE cable

Ethernet cable

PCI bus

Label A is _____.

Label B is _____.

Label C is _____.

Label D is _____.

Label E is _____.

Label F is _____.

Label G is _____.

Describe the functionality of each of the following components (in 2 sentences

or less):

Microprocessor:

RAM:

Bus:

Expansion card:

Label A is _ Power supply ____.

Label B is __ Cooling fan ___.

Label C is __ Expansion slot ___.

Label D is ___Expansion card __.

Label E is __ Motherboard ___.

Label F is ___ Disk drives __.

Label G is _ IDE cable ____.

Microprocessor:

Processes instructions stored in main memory.

RAM:

Stores data and instructions temporarily.

Bus:

Pathway through which data is transferred from one part of a computer to another.

Expansion card:

Enables a computer to control peripheral devices such as the monitor and the

microphone.

14． Boot Process

a. What are two functions of the boot process?

The boot process ensures that crucial components of the computer system such as the

memory, screen display, etc. are functional. It also loads the operating system from the hard

四川大学计算机导论期末复习资料总结。

disk into memory to enable the computer to be operational.

b. Describe the steps involved in a POST (include the information BIOS displays

at the end of POST).

In a POST (Power-On Self Test), first the video cards is enabled, then the amount of

DRAM installed is determined, a memory test maybe performed, depending on the

BIOS parameter setting, then the BIOS identifies expansion cards and adapters that

are present and initializes any it finds. At the end of POST, the BIOS displays system

configuration information such as the type of processor installed, cache memory

information, disk drives found, addresses of serial or parallel ports, and a list of

expansion cards detected.

c. Fill in the following chart by arranging the steps of the boot process below in

order.

Copy BIOS to RAM Execute BIOS program Identify peripheral devices Load device drivers POST Search for Master Boot Record and load the operating

system

15. Cryptography

In this section, you will encode/decode simple messages using different

cryptography methods.

a. Consider the alphabet shift cipher. Complete the following table:

四川大学计算机导论期末复习资料总结。

b. What is the maximum number of ways you can replace a character using the

above alphabet shift cipher? What is the size of the key space? What is a

weakness of the alphabet shift cipher above?

25

25

The alphabet -shift cipher only provides for a small number of possible ways to

encrypt a message. It is so simple that can be broken quickly by brute force.

c. How does using a secret passphrase as the encryption key compare to using

the alphabet shift cipher?

Compare to using the alphabet shift cipher, using a secret passphrase as the

encryption key greatly expands the keyspace up to 26n for a substitution cipher

and the cipher can not be broken easily.

Let us try using a passphrase to encrypt the message "Meet at noon." with a

larger key space. The key is "CBA". In this case, only encrypt alphabet letters.

d. What is the encrypted message?

the encrypted message is : Pgfw cu qqpq.

16. Data Representations in a Computer System

The Extended ASCII chart below shows characters and their binary

representations. Use the chart below and a calculator to answer the

following questions:

四川大学计算机导论期末复习资料总结。

Figure 1 ASCII code

You can obtain the binary representation of a word by concatenating the

ASCII values of each letter. For example, “SSD2” in binary representation is

01010011 01010011 01000100 00110010.

a. “Fun” in binary representation is b. “Play” inrepresentation.

c. 01100011 01100001 01110010 01100101 01100101 01110010 01110011 is

a. “Fun” in bb. “Play” in binary representation is representation.

c. 01100011 01100001 01110010 01100101 01100101 01110010 01110011 is

四川大学计算机导论期末复习资料总结。

d. 0x7374617274 is a hexadecimal representation of the ASCII string

17. Batch File Creation

In this section, you will interface with the operating system using DOS commands.

For each of the following tasks, list the correct DOS command. Note: While it is not necessary to perform these tasks on a computer, the assignment is structured for each task to be completed in sequence; that is to say, a task may depend on the state created by previous tasks.

a.

b.

c.

d.

e.

f.

g.

h. Name the batch file EXDIR.BAT. Include your name as a remark in EXDIR.BAT. Include the creation date as a remark in EXDIR.BAT. Include the function of EXDIR.BAT as a remark in EXDIR.BAT- redirects the output of “dir C:\” to a file named by the user. The filename provided by the user is the first argument. A valid switch for the command dir is the optional second argument. If the file named by the user already exists, EXDIR.BAT immediately generates an error message and then exits without executing dir. The error message generated by EXDIR.BAT must display, "filename already

exists, aborting EXDIR."

Write down your batch file code.

REM Lei Zhang

REM 2006-02-18

REM Redirect the output of dir c:\ to a file named

@ECHO off

if EXIST %1 goto ERRORMSG

if EXIST %2 goto second

:second

dir c:\ %2 > %1

goto END

dir c:\ > %1

goto END

:ERRORMSG

ECHO The %1 already exsits, aborting EXDIR

:END

18. XML and HTML

四川大学计算机导论期末复习资料总结。

One necessary component to facilitate electronic commerce is the capability to exchange data over varying systems. In this section, you will strengthen your knowledge of XML as a portable language that enables data to be handled by any computer system.

a. What does the term “XML” stand for? What is the function of XML tags, and how does the function of XML tags differ from the function of HTML tags?

XML is a text document markup language whose full name is extensible Markup Language.

XML tags is used to describe what a piece of text means.

The XML tags differ from HTML tags mainly in two functions:

(1)One is that XML tags is to describe what a piece of text means such as <phone> 123</phone> while HTML tags primarily concern with how text should be displayed.

(2)Another is that XML has no predefined tags while HTML does. Users have the freedom to define their own tags in XML.

b. Contrast the flexibility of using XML tags and HTML tags.

HTML tags, which are predefined, limit us to write HTML documents using only tags that are defined in the HTML standard. However, XML has no such predefined tags. XML permits users to have the freedom to define their own tags.

c. What is one reason why storing data in XML may be preferred to enable multiple systems to exchange data?

XML allows the author to define his own tags and his own document structure. It is composed of text and it is software and hardware independent so that any computer system would be able to interpret an XML document. Due to XML's flexibility and interoperability, it is becoming the standard for exchanging data over the Internet. d. If there are two files, and on your Desktop.

Open display.html using Notepad.exe to see the content of the HTML file. Note that the references used to embed the xml file are highlighted in bold font below:

<html>

<body>

<xml id="movies" src="Movies100EX.xml"></xml>

<table border="1" datasrc="#movies">

<tr>

<td><span datafld="Title"></span></td>

<td><span datafld="Year"></span></td>

</tr>