Kapitel 1

Question 0

Iist the five major hardware components of a computer system.

Answer 0

The Central Processing Unit (CPU), main memory, secondary storage devices, input devices, output devices.

Question 1

Why is the computer used by so many different people, in so many different professions?

Answer 1

Because the computer can be programmed to do so many different tasks.

Question 2

Internally, the CPU consists of what two units?

Answer 2

Arithmetic and Logic Unit (ALU), and Control Unit.

Question 3

Describe the steps in the fetch/decode/execute cycle.

Answer 3

Fetch: The CPU’s control unit fetches the program’s next instruction from main memory.

Decode: The control unit decodes the instruction, which is encoded in the form of a number. An electrical signal is generated.

Execute: The signal is routed to the appropriate component of the computer, which causes a device to perform an operation.

Question 4

What is a memory address? What is its purpose?

Answer 4

A unique number assigned to each section of memory. The address is used to identify a location in memory.

Question 5

Explain why computers have both main memory and secondary storage.

Answer 5

Program instructions and data are stored in main memory while the program is operating. Main memory is volatile, and loses its contents when power is removed from the computer. Secondary storage holds data for long periods of time—even when there is no power to the computer.

Question 6

What does the term multitasking mean?

Answer 6

It means that an operating system is capable of running multiple programs at once.

Question 7

Describe the difference between a key word and a programmer-defined symbol.

Answer 7

A key word has a special purpose, and is defined as part of a programming language. A programmer-defined symbol is a word or name defined by the programmer.

Question 8

Describe the difference between operators and punctuation symbols.

Answer 8

Operators perform operations on one or more operands. Punctuation symbols mark the beginning or ending of a statement, or separates items in a list.

Question 9

Describe the difference between a program line and a statement.

Answer 9

A line is a single line as it appears in the body of a program. A statement is a complete instruction that causes the computer to perform an action.

Question 10

Why are variables called “variable”?

Answer 10

Because their contents may be changed.

Question 11

What happens to a variable’s current contents when a new value is stored there?

Answer 11

The original value is overwritten.

Question 12

What is a compiler?

Answer 12

A compiler is a program that translates source code into an executable form.

Question 13

What is a syntax error?

Answer 13

Syntax errors are mistakes that the programmer has made that violate the rules of the programming language. These errors must be corrected before the compiler can translate the source code.

Question 14

What is byte code?

Answer 14

The Java compiler translates Java source code into byte code, which is an interme­diate language. The Java Virtual Machine executes the byte code instructions.

Question 15

What is the JVM?

Answer 15

The Java Virtual Machine (JVM) is a program that reads Java byte code instructions and executes them as they are read. In other words, it interprets byte code instruc­tions. You can think of the JVM as a program that simulates a computer whose machine language is Java byte code.

Question 16

What four items should you identify when defining what a program is to do?

Answer 16

The program’s purpose, input, process, and output.

Question 17

What does it mean to “visualize a program running”? What is the value of such an activity?

Answer 17

Before you create a program on the computer, it is often a good idea to imagine what the computer screen will look like while the program is running. If it helps, draw pictures of the screen, with sample input and output, at various points in the program.

Question 18

What is pseudocode?

Answer 18

A cross between human language and a programming language. Pseudocode is especially helpful when designing an algorithm. Although the computer can’t understand pseudocode, programmers often find it helpful to write an algorithm in a language that’s “almost” a programming language, but still very similar to natural language.

Question 19

Describe what a compiler does with a program’s source code.

Answer 19

A compiler translates source code into an executable form.

Question 20

What is a runtime error?

Answer 20

A runtime error is an error that occurs while the program is running. These are usually logical errors, such as mathematical mistakes.

Question 21

Is a syntax error (such as misspelling a key word) found by the compiler or when the program is running?

Answer 21

Syntax errors are found by the compiler.

Question 22

What is the purpose of testing a program with sample data or input?

Answer 22

You can provide sample data and predict what the output should be. If the program does not produce the correct output, a logical error is present in the program.

Question 23

In procedural programming, what two parts of a program arc typically separated?

Answer 23

Data and the code that operates on the data.

Question 24

What are an object’s attributes?

Answer 24

The data contained in an object.

Question 25

What are an object’s methods?

Answer 25

The procedures, or behaviors, that an object performs.

Question 26

What it encapsulation?

Answer 26

Encapsulation refers to the combining of data and code into a single object.

Question 27

What is data hiding?

Answer 27

Data hiding refers to an object’s ability to hide its data from code that is outside the object. Only the object’s methods may then directly access and make changes to the object’s data. An object typically hides its data, but allows outside code to access the methods that operate on the data.