Overview Of Computers and Programming
1.1 Electronic Computers Then and Now These early computers used vacuum tubes
as their basic electronic component. Technological advances in the design and
manufacture of electronic components led to new generations of computers that
were considerably smaller, faster, and less expensive than previous ones. • The
Intel Atom processor chip contains the full circuitry of a central processing
unit in an integrated circuit whose small size and low power requirements make
it suitable for use in mobile internet devices • (Intel Corporation Pressroom
Photo Archives) computer chip (microprocessor chip) a silicon chip containing
the circuitry for a computer processor hardware the actual computer equipment
software the set of programs associated with a computer program a list of
instructions that enables a computer toperform a specific task binary number a
number whose digits are 0 and 1 1.2 Computer Hardware Essentially, most consist
of the following components: ■ Main memory ■
Secondary memory, which includes storage devices such as hard disks, CDs, DVDs,
and flash drives ■ Central processing unit ■
Input devices, such as keyboards, mouses, touch pads, scanners, joysticks ■
Output devices, such as monitors, printers, and speakers Memory Memory is an
essential component in any computer. memory cell an individual storage location
in memory address of a memory cell the relative position of a memory cell in
the computer’s main memory contents of a memory cell the information stored in
a memory cell, either a program instruction or data stored program concept a
computer’s ability to store program instructions in main memory for execution
byte the amount of storage required to store a single character bit a binary
digit; a 0 or a 1 1000 Memory Cells in Main Memory 00101100 Byte Bit
Relationship Between a Byte and a Bit data storage setting the individual bits
of a memory cell to 0 or 1, destroying its previous contents data retrieval
copying the contents of a particular memory cell to another storage area random
access memory (RAM) the part of main memory that temporarily stores programs,
data, and results. read-only memory (ROM) the part of main memory that
permanently stores programs or data volatile memory memory whose contents
disappear when the computer is switched off secondary storage units such as
disks or flash drives that retain data even when the power to the drive is off
disk thin platter of metal or plastic on which data are represented by
magnetized spots arranged in tracks optical drive device that uses a laser to
access or store data on a CD or DVD flash drive device that plugs into USB port
and stores data bits as trapped electrons file named collection of data stored
on a disk directory a list of the names of files stored on a disk subdirectory
a list of the names of files that relate to a particular topic. Central
Processing Unit central processing unit (CPU) coordinates all computer
operations and performs arithmetic and logical operations on data fetching an
instruction retrieving an instruction from main memory, register high-speed
memory location inside the CPU multiprocessor a computer with more than one CPU.
Input/Output Devices cursor a moving place marker that appears on the monitor
function keys special keyboard keys used to select a particular operation;
operation selected depends on program being used mouse an input device that
moves its cursor on the computer screen to select an operation icon a picture
representing a computer operation hard copy a printed version of information
Computer Networks local area network(LAN) computers, printers, scanners, and
storage devices connected by cables for intercommunication digital subscriber
line ( DSL connection ) or fiber-optics telephone line, the associated file
server the computer in a network that controls access to a secondary storage
device such as a hard disk wide area network (WAN) a network such as the Internet
that connects computers and LANs over a large geographic area World Wide Web
(WWW) a part of the Internet whose graphical user interfaces make associated
network resources easily navigable graphical user interface (GUI) pictures and
menus displayed to allow user to select commands and data modem a device that
converts binary data into audio signals that can be transmitted between
computers over telephone lines DSL connection (digital subscriber line) a
high-speed Internet connection that uses a telephone line and does not
interfere with simultaneous voice communication on the same line cable Internet
access two-way highspeed transmission of Internet data through two of the
hundreds of channels available over the coaxial cable that carries cable television
signals 1.3 Computer Software Operating System operating system (OS) software
that controls interaction of user and computer hardware and that manages
allocation of computer resources booting a computer loading the operating
system from disk into memory Application Software application software used for
a specific task such as word processing, accounting, or database management
install make an application available on a computer by copying it to the
computer’s hard drive. Computer Languages machine language binary number codes
understood by a specific CPU assembly language mnemonic codes that correspond
to machine language instructions high-level language machine-independent
programming language that combines algebraic expressions and English symbols compiler
software that translates a highlevel language program into machine language
source file file containing a program written in a high-level language; the
input for a compiler syntax grammar rules of a programming language object file
file of machine language instructions that is the output of a compiler linker
software that combines object files and resolves crossreferences to create an
executable machine language program integrated development environment (IDE)
software package combining a word processor, compiler, linker, loader, and
tools for finding errors. Executing a Program input data the data values that
are scanned by a program program output the lines displayed by a program 1.4
The Software Development Method Software Development Method 1. Specify the
problem requirements. 2. Analyze the problem. 3. Design the algorithm to solve
the problem. 4. Implement the algorithm. 5. Test and verify the completed
program. 6. Maintain and update the program. abstraction the process of
modeling a problem by extracting the essential variables and their
relationships algorithm a list of steps for solving a problem top-down design
breaking a problem into its major subproblems and then solving the subproblems
stepwise refinement development of a detailed list of steps to solve a
particular step in the original algorithm desk checking the step-by-step
simulation of the computer execution of an algorithm. 1.5 Applying the Software
Development Method CASE STUDY Converting Miles to Kilometers PROBLEM Your
summer surveying job requires you to study some maps that give distances in
kilometers and some that use miles. You and your coworkers prefer to deal in
metric measurements. Write a program that performs the necessary conversion.
ANALYSIS The first step in solving this problem is to determine what you are
asked to do. You must convert from one system of measurement to another, but
are you supposed to convert from kilometers to miles, or vice versa? The
problem states that you prefer to deal in metric measurements, so you must
convert distance measurements in miles to kilometers. Therefore, the problem
input is distance in miles and the problem output is distance in kilometers .
To write the program, you need to know the relationship between miles and
kilometers. Consulting a metric table shows that one mile equals 1.609
kilometers. The data requirements and relevant formulas are listed below. miles
identifies the memory cell that will contain the problem input and kms
identifies the memory cell that will contain the program result, or the problem
output. DATA REQUIREMENTS Problem Input miles /* the distance in miles*/
Problem Output kms /* the distance in kilometers */ Relevant Formula 1 mile =
1.609 kilometers DESIGN Next, formulate the algorithm that solves the problem. Begin
by listing the three major steps, or subproblems, of the algorithm. ALGORITHM
1. Get the distance in miles. 2. Convert the distance to kilometers. 3. Display
the distance in kilometers. Now decide whether any steps of the algorithm need
further refinement or whether they are perfectly clear as stated. Step 1
(getting the data) and step 3 (displaying a value) are basic steps and require
no further refinement. Step 2 is fairly straightforward, but some detail might
help: Step 2 Refinement 2.1 The distance in kilometers is 1.609 times the
distance in miles. We list the complete algorithm with refinements below to
show you how it all fits together. The algorithm resembles an outline for a
term paper. The refinement of step 2 is numbered as step 2.1 and is indented
under step 2. ALGORITHM WITH REFINEMENTS 1. Get the distance in miles. 2.
Convert the distance to kilometers. 2.1 The distance in kilometers is 1.609
times the distance in miles. 3. Display the distance in kilometers. Let’s desk
check the algorithm before going further. If step 1 gets a distance of 10.0
miles, step 2.1 would convert it to 1.609 _ 10.00 or 16.09 kilometers. This
correct result would be displayed by step 3. FIGURE 1.13 Miles-to-Kilometers
Conversion Program 1. /* 2. * Converts distance in miles to kilometers. 3. */
4. #include /* printf, scanf definitions */ 5. #define KMS_PER_MILE 1.609 /*
conversion constant */ 6. 7. int 8. main(void) 9. { 10. double miles, /* input
- distance in miles. */ 11. kms; /* output - distance in kilometers */ 12. 13.
/* Get the distance in miles. */ 14. printf(“Enter the distance in miles>
”); 15. scanf(“%lf”, &miles); 16. 17. /* Convert the distance to
kilometers. */ 18. kms = KMS_PER_MILE * miles; 19. 20. /* Display the distance
in kilometers. */ 21. printf(“That equals %f kilometers.\n”, kms); 22. 23.
return (0); 24. } Sample Run Enter the distance in miles> 10.00 That equals
16.090000 kilometers. 1.6 Professional Ethics for Computer Programmers Privacy
and Misuse of Data computer theft (computer fraud) Illegally obtaining money by
falsifying information in a computer database Computer Hacking virus Code
attached to another program that spreads through a computer’s disk memory,
disrupting the computer or erasing information worm A virus that can disrupt a network
by replicating itself on other network computers Plagiarism and Software Piracy
software piracy Violating copyright agreements by illegally copying software
for use in another computer Misuse of a Computer Resource Computer system
access privileges or user account codes are private property. These privileges
are usually granted for a specific purpose—for example, for work to be done in
a particular course or for work to be done during the time you are a student at
your university. The privilege should be protected; it should not be loaned to
or shared with anyone else and should not be used for any purpose for which it
was not intended. When you leave the institution, this privilege is normally
terminated and any accounts associated with the privilege will be closed.
Computers, computer programs, data, and access (account) codes are like any
other property. If they belong to someone else and you are not explicitly given
permission to use them, then do not use them. If you are granted a use
privilege for a specific purpose, do not abuse the privilege or it will be
taken away. Legal issues aside, it is important that we apply the same
principles of right and wrong to computerized property and access rights as to
all other property rights and privileges. If you are not sure about the
propriety of something you want to do, ask first. As students and professionals
in computing, we set an example for others. If we set a bad example, others are
sure to follow. JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ
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