CMSC 131

What does IDE stand for?

Integrated Development Environment

What IDE will we use in class this semester?

Eclipse

What does CPU stand for?

Central Processing Unit

Define the term "bit".

A "binary digit" -- either 0 or 1.

Define the term "byte".

A sequence of 8 bits.

What is "hardware"? Name some examples.

Physical components of the computer. (Things you can "touch"). Examples include: CPU, RAM chips, mother board, disk drives, monitor, mouse, keyboard, cables.

What is "software"? Name some examples.

These are the "programs" or "apps" that you can run on a computer. Examples: Internet browsers, games, word processors, spreadsheet programs, the operating system, etc.

Name several different operating systems.

Windows, macOS, Android, ios.

Give some examples of secondary memory devices.

Hard drives, flash memory devices, CD's , DVD's

What is the advantage of primary memory over secondary?

It is typically much faster.

What is the advantage of secondary memory over primary?

It is permanent. (Also usually there is more of it!)

What does I/O stand for? Give some examples of I/O devices.

Input/Output. These are devices that allow you to communicate with the computer: monitor, keyboard, mouse, printer, etc.

How many different combinations of 0's and 1's can be represented using 7 bits?

2^7 = 128

How many bytes are in a kilobyte? Megabyte? Gigabyte?

2^10, 2^20, 2^30 or 1000, 1 million, 1 billion

Name four things that the operating system does for you.

-Process management
-Memory management
-Primitive I/O
-Windowing
-Primitive network control
-Security management

What do you call the language that the CPU uses (0's and 1's represent instructions in this language).

Machine Language

How does "assembly language" relate to your answer to the previous question?

Assembly language is a mnemonic representation of machine language.

When your Java program is compiled, what type of file is created? (Hint: It is NOT machine language.)

Bytecode

What does it mean for someone to say that a Java program is "portable"?

The same bytecode will run successfully on any platform (provided that the Java Virtual Machine (JVM) is available.)

TRUE/FALSE: Inserting unnecessary spaces and/or blank lines could cause your Java program to malfunction.

False, java ignores white space

List the four Java primitive types that can be used to store integer values.

long, int, short, byte

How much memory is required to store long?

8 bytes

How much memory is required to store int?

4 bytes

How much memory is required to store short?

2 bytes

How much memory is required to store byte?

1 byte

What advantage do you gain from using one of the types of integer types that requires MORE memory?

You can store a wider range of values (larger values).

List the two Java primitive types that can be used to store floating point values.

float, double

How much memory is required to store a double?

8 bytes

How much memory is required to store a float?

4 bytes

What advantage do you gain from using double instead of float?

more precision (it will retain more digits) (recall a double uses 8 byte and a float uses 4 bytes)

List the two Java primitive types that are used to store values that are not numbers.

char and boolean

Write a statement that declares a variable named counter of type int, and stores the value 182 in the variable.

int counter = 182;

Write a statement that simultaneously declares three variables of type boolean, named x, y, and z.

boolean x, y, z;

What values can a boolean variable achieve?

true or false

Write a java class called "Fred". Put in a main method. Have the main method store your age in a variable named age. Then main should print out a line that has your name, followed by your age. (Use a ?string literal? for your name, but use the variable to access your age.)

public class Fred { public static void main(String[] args) { int age = 12; System.out.println("Fawzi Emad, age is " + age); } }

What are the two styles of java comments?

// one line comment
/* multiple line comment */

Is the following statement valid: int x = 34.7;

no (type mismatch)

Is the following statement valid: double y = 12;

yes

Is the following statement valid: boolean q = 17 < 25;

yes

What does modulus do?

Return the remainder

Should you compare two strings with the == operator?

No

What should you do to compare two strings?

x.equals(y)

What is concatenation?

Joining two strings together

What operator do you use to concatenate Strings?

+

What are literals?

The actual value used in code

Give an example of a literal String?

"hi"

Give an example of a literal char?

'x'

Give an example of a literal long?

32L

Give an example of literal int?

16

Give an example of literal float?

15.7F

Give an example of literal double?

373.2

Give an example of literal boolean?

true

What is the "normal" base?

Base 10

How do you convert to different bases?

Divide by the base # into the base 10 number and put down the remainder from right to ledt\\ft

How do you convert from different bases back to base 10?

Multiply the number by the base value to the power of what position it is in

What are the important bases for CS?

2 (bianary) and 16 (hexadecimal)

What values can base 2 have?

1 and 0

What values can hexadecimal have?

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F

Each digit in hex corresponds to exactly how many digits in binary?

4

How do you convert from hex to binary?

write each digit as it should be in binary and put them altogether

How do you convert from binary to hex?

Starting from the right break the number up into 4 digit chunks (pad to the left if needed), then determine the value and write it in hex

What is a CPU and what does it do?

Central Processing Unit, it is the brain of the computer and it runs the machine code. There are multiples cores and there are often 2 "threads" per core

What is RAM?

Random Access Memory or Primary Memory

What are Secondary Memory Devices?

Hard drives, Solid state drives, USB thumb drives, cd/dvd

How do input/output devices work? Give an example?

It is from the perspective of the computer. Keyboard is input.

Define bit?

A binary digit (a 0 or 1)

Define byte?

a sequence of 8 bits

Define ram?

a sequences of cells containing 8 bits

How many permutations can a cell in a ram hold?

2^8

What is the formula for finding the amount of permutations given k bits?

2^k

How many bytes is a kilobyte?

1024 bytes (kB) or 1000 bytes (kb)

How many bytes is a megabyte?

2^20 bytes (mB) or 1 million bytes (mb)

How many bytes is a gigabyte?

2^30 bytes (gB) or 1 billion bytes (gb)

How many bytes is a terabyte?

2^40 bytes (tB) or 1 trillion bytes (tb)

How are non-negative numbers stored?

They are converted to binary and then padded with leading 0s

How are negative numbers stored?

Using two's complement

Explain the method for turning a number into twos complement.

Turn the number into binary, pad with extra zeros to take up all the bits of space, flip the numbers and add 1

How are floating point numbers stored?

Basically they are stored in scientific notation

How is text stored?

It is stored in different formats based on context, however the old standard was ASCII and the new way is Unicode?

What does ASCII stand for?

American Standard Code for Information Interchange

Explain the difference between ASCII and Unicode and why we made the switch?

ASCII is only 1 byte per character v. Unicode which is two bytes per character (as per UTF-16 although there are different versions), which allows us to convey a wider range of symbols

What are some popular operating systems?

Laptops: Windows, MacOS, Linux, Unix
Mobile: iOS, Android

What does the operating system do?

-Process Management
- Memory Management
- Primitive I/O
- GUI (Windowing)
-Network Control (TCP)

What does process management mean?

Queue the processes and do process scheduling

What does memory management mean?

Allocates and deallocates RAM

What does primitive I/O mean?

Operation system + installed drivers manage technical operations when printing

What is machine language?

Also called machine code, machine language are primitive instructions that the computer knows how to do because the computer doesn't know java

What is assembly language?

It is the lowest language a human can understand easily, basically it is a "readable" machine language

What are some examples of higher level languages?

- C
- C++
- Pascal
- Ruby
- Python
- Java
- Lisp
- Cobol
- Fortran

What are the two was high-level code is translated to machine code?

Compiled and Interpreted

How do compilers work? What are the pros and cons?

Compilers translate source code to an executable machine code file all at once (.exe on Windows, .dmg on macOS). The pro is that it is fast but it is not portable because your specific computer has to compile it so there are different versions for different operating systems

How do interpreters work? What are the pros and cons?

As the program is running, the code is translated line-by-line live. The pro is that it is portable because the source code is the same for everyone as long as they have an interpreter. The cons are that it takes a little longer because it requires CPU time

How does Java run a program?

Java uses a compiler and interpreter. Essentially, Java compiles the source code into a universal bytecode file which is easily portable. When the bytecode file is ran, it is interpreted line by line

What is the vague definition of a Object?

things that interact with each other (nouns)

What is the vague definition of a Class?

a description of an Object (definition)(blueprint)

What is the vague definition of a Method?

A chunk of code that has a name

What is the main method?

Where the program starts

What are statements?

A series of instructions that are sequential but not connected

What is the main method prototype?

public static void main (String args[])

What does System.out.print() do?

Prints stays on the same line