discuss the pillars of info assurance (ciana) and apply them to concepts, tools, scenarios, etc. ...

By Now, You Should Be Able To… Discuss the Pillars of Info Assurance (CIANA) and

apply them to concepts, tools, scenarios, etc. Convert between binary, hex, decimal, and

ASCII. Discuss the primary functions/services that an

Operating System provides. Discuss processes, user accounts, permissions. Comfortably navigate the file/folder structure of

Windows & Unix via the shell (command line). Utilize multiple commands (win & unix) via the

shell: dir, ls, copy, move, mkdir, rmdir, whoami, hostname, ipconfig, ping, etc. Be proactive w/ EI, MGSP, etc.!

PROGRAMMINGPART IUSNA SI110

LT BRIAN KIEHLLEAHY 373 | 410.293.0938

[email protected]

Programs

Files containing instructions for the CPU Can write a program in this

manner Almost no one does

Programs are written in a programming language Set of commands that are

converted to CPU instructions Commands are written ahead of

time and then compiled or interpreted

We will be using JavaScript as our programming language

31 c0 31 db 31 d2 31 c9 b0 04 b3 01 59 b2 05 cd 80 31 c0 b0 01 31 db cd 80 e8 e2 ff ff ff 68 65 6c 6c 6fWho wants to write a program like

this?

Believe it or not, this is MUCH easier.

Programming Part I 4

Compiled vs. Interpreted Languages

Compiled languages Commands are converted to CPU instructions

before the program executes Machine code stored in program file

Interpreted languages Commands are evaluated and converted to

CPU instructions at run time Requires an interpreter program Programming language code stored in program

file JavaScript is an interpreted language


Javascript

A scripting language for browsers. Every browser includes a Javascript

interpreter Javascript programs are not meant to run

directly on a physical machine, but instead "run on the browser“…which itself is a Program running on the physical machine. This kind of "program running within a

program", is actually extremely common, is often referred to as a script.


JS Statements & Expressions

A program is a collection of statements and expressions Translated into CPU instructions

Statement is a command to perform an action document.write("Hello World"); Action can be to evaluate an expression

Expression is a statement that evaluates to a value x = x + 1;

Statements and expressions are terminated with the ‘;’ character. Not required in JavaScript, but good practice


Literals vs. Variables

A literal is a constant value 2016 “a string”

A variable is a symbolic name for a known or unknown value Consider it as a “temporary container” for a

value …and the value stored in that container can

change When the variable’s name is used, it

evaluates to the value in the container


Operators

Program element that is applied to one or more operands in an expression or statement

Types Arithmetic Assignment Comparison Boolean

We will cover comparison and Boolean operators later


JS Arithmetic OperatorsOperat

orDescription Exampl

eResult (x)

+ Addition x = y + 2;

7

- Subtraction x = y – 2;

3

* Multiplication x = y * 2;

10

/ Division x = y / 2;

2.5

% Modulus (remainder) x = y % 2;

1

Note: y = 5 for all examples

• Order of Operations maintained as before• Student Exercise: Enter an expression to sum the integers from 1 to 10

• Pull up: <a href="http://rona.cs.usna.edu/~si110/resources/interpreterBare.html">interpreter</a>


Math functions: Beyond simple arithmetic ops, JS has established math functions: math functions:, Math.sin( ), Math.cos( ), Math.log( ), Math.exp( ),

Math.sqrt( ), Math.floor( ), etc. Ex: Math.sqrt(a): Yields square root of variable a complete reference of Math functions and constants

Student exercise: Write a single expression that gives exactly the answer to the following problem: calculate the hypotenuse of a right triangle with base sides 68 and 23.5.

NOTE: unfortunately, there is no exponentiation! Student exercise: Write a single expression that gives exactly

the answer to the following problem: Your restaurant bill is $73.50. What would you tip if you wanted to give at least an 18% tip, but you wanted the tip to be a whole number of dollars?

JS Arithmetic & other Operators

http://www.w3schools.com/jsref/jsref_obj_math.asp


Now…Using Variables

var x;

x = 5;

x = 2000;

x = x + 2;

5

20005

2000 + 2 = 2002


Variables: Javascript lets you define variables, which are simply names that point to values.

Once a name is declared as a variable, that name evaluates to the most recent value it points to.

Usually, we could declare and assign simultaneously in the same line,

e.g.: var x = Math.sqrt(17);

In Javascript: x = x + 1 …makes sense, because it assigns x a new value: its original value + 1

What you want to do How it is scripted

Declare name x as a variable:

var x;

“assign” name x a value: x =0 or x=Math.sqrt(17)

evaluate name x to get its value:

x

Now…Using Variables


Variable Types Identifies the type of data a value (either

literal or variable) represents JavaScript types

Number String Boolean Function Object

We will focus on Numbers and Strings Booleans to a lesser extent


Variable Changes

1. var x = 32. var z = 23. x = x + z4. x = x +

z*z

What is value of x What is value of z


Numbers

Literal type used to represent a numeric value Whole numbers (3, 1, 4) Decimal numbers (3.14)

Various operations can be performed Basic arithmetic

Usual arithmetic operation ordering applies Math functions

Math.sin(x), Math.exp(x), Math.sqrt(x), etc. JavaScript provides defined mathematical constants

Math.PI, Math.E, etc. Operations, functions, and constants can be

combined Math.sqrt(Math.PI * 3 * 3);


Strings

Every value in Javascript has a “type”, numbers are one of them, “strings” are another

String is a sequence of characters Enclosed within single or double quotes ( ‘ or “ ) Zero-length string (i.e., no characters) is called an

“empty string” Examples

‘foo’ “bar” ‘3’ “3.14” “Hello, world!” “” this is the empty string (zero length)


Escape Characters

A sequence used to insert special characters into a string literal which would otherwise cause a “syntax error” Backslash (\) followed by sequence that

denotes the character Often used to print characters that

Are difficult (or impossible) to type Would be interpreted as part of the program’s

syntax


Escaping Examples

\’ or \” – insert a single or double quote Enter this in the line interpreter: “I said “hello”.”

What happened? Correct: “I said \”hello\”.”

Enter this in the line interpreter: ‘This can’t work!’ Correct: ‘This can\’t work!’

\n – insert a new line “This string \nhas two lines” prints as:

This stringhas two lines

\\ - insert a backslash “The directory is c:\navy” prints as:

The directory is c:avy

Correct: “The directory is c:\\navy”


Working with Strings

+ operator Used to concatenate (join) strings together

var message = “Hello, ” + “world!”; yields the new string “Hello, world!”

JavaScript automatically interprets operators based on data types 7 + 5 yields 12 “7” + “5” yields “75”


String Subscripts A String is a collection of zero or more characters If you want to pick out a character from a string at a

certain position, you can do it by "subscripting". Subscripting allows the programmer to reference a specific character in a String

Positions of characters within a string by is called an index. The trick is that index position 0 corresponds to the first character

in a string, which may be counter-intuitive. The syntax is string[index position].

So, if var x = "hard", the expression x[0] evaluates to the letter h, the expressions x[1] evaluates to a, etc.

The referenced character is at the position (index) denoted by the subscript

If var foo = “Hello, world!”; what would foo[3] would evaluate to?


String Functions JavaScript Strings have some built-in functions

var_name.length Returns the number of characters in a string “Hello”.length what does this yield?

var_name.charAt(x) Returns the character at position x “Hello”.charAt(4) what does this yield?

var_name.charCodeAt(x) Returns the ASCII value of the character at position x “Hello”.charCodeAt(4) what does this yield?

String.fromCharCode(x) Returns a string consisting of the character represented by

the ASCII value x String.fromCharCode(67) what does this yield?


“Type” Determination

typeof operator Special operator used to determine the type of

a value: commonly a “string” or a “number” Examples

typeof(1989) → What “type” does this yield? typeof(“2016”) → What “type” does this yield

Can call typeof for an expression typeof(2000 + 2) → Number typeof(“200” + “2”) → String

Programming Part II 23

Type Conversion

JavaScript [tries to] automatically convert numbers to strings and strings to numbers when it deems necessary Implicit conversion

Can also perform explicit conversion Number(x)

Attempts to convert the argument to a Number String(x)

Attempts to convert the argument to a String

Programming Part II 24

Type Examples

typeof(2016 + 2); Number → 2018

typeof(“201” + ”6”); String → “2016”

typeof(1008 * “2”); Number → 2016

typeof(201 + “6”); String → “2016”

typeof(2000 + Number(“16”)); Number → 2016

typeof(“20” + String(16)); String → “2016”

QUESTIONS?

Operating Systems Part II 25

discuss the pillars of info assurance (ciana) and apply them to concepts, tools, scenarios, etc. ...

Documents