2018 ~ Kavya

CMD Prompts and Commands

Command Prompt is a command line interpreter application available in most Windows operating systems. It is used to execute entered commands.

Most of those commands automate tasks via scripts and batch files, perform advanced administrative functions, and troubleshoot or solve certain kinds of Windows issues.

Command Prompt is officially called Windows Command Processor, but it is also sometimes referred to as the command shell or cmd prompt or even by its filename, cmd.exe. Go to run option and type cmd to open command window.

Some of the Commonly used Commands are:
1. cd (Change Directory): The cd command, also known as chdir (change directory), is a command-line OS shell command used to change the current working directory in operating systems.

Sample File Lookup

Now a days we store lot of data (documents,images, music,video etc) in our computer finding a file sometimes little bit difficult.

This can be done by grouping and arranging the files in many ways.

Open the drive that contains files and right click in the empty area and select either "sort by" or "group by" option.

Sorting Techniques:

Sort by Name: We can sort the files by name in ascending or descending order.

Sort by Date Modified: If we sort by date modified we can see the recently modified/used files in ascending or descending order.

Sort by Size: If we sort by size in descending order the bigger size files will appear first and in ascending order smaller size will appear first. We can also sort by type and other techniques to get file fatser.

Grouping Techniques:

Group by Name: We can group the files by name in ascending or descending order.

Group by Date Modified: If we group by date modified we can see the recently modified/used files in ascending or descending order.

Group by Type: We can group the files by type in ascending or descending order.

DXF File Format

DXF is short for Drawing Interchange Format or Drawing Exchange Format. Commonly known as AutoCAD DXF format, is a CAD data file format.

It was developed by Autodesk to enable data interoperability between AutoCAD and other programs. DXF file format was first introduced in 1982.

The key purpose of this format was to produce the exact representation of AutoCAD native DWG files on other applications.

For many years, the importing process of DXF files had been very difficult because of the unavailability of specifications of the format.

Presently the format specifications are available as PDF but this format is rarely used in AutoCAD applications.

We can use a range of programs to view/edit DFX files.

The ASCII DXF file is a complete representation of a drawing in ASCII text form. Data is represented with numbers and strings of text that you can easily interpret using the specification document.

DXF Editor:

DXF Viewer:

CAD File Format

CAD stands for Computer Aided Design.

CAD software is used to create 2D and 3D graphical representation of physical objects.

This software is used by engineers, architects and other professionals to create drawings or technical illustrations.

It's software is used to increase the productivity of the designer, improve the quality of the design.

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CAD file formats generally fall into one of two categories–either Native or Standards-Based.

Native file formats are under the control of a particular CAD software maker who can choose to change them at any time.

A Standards-Based format is in the hands of some standard-making organization which gets to decide when and how the format changes.

Some of the cad File Formats are:

DXF:

DXF Stands for Drawing Exchange Format File.

DXF is open source used by almost all CAD softwares.

It supports only 2D lines, text, polygons and circles.

DXF is used when we want to share drawings between different CAD or vector based programs.

DWG:

DWG (an abbreviation for ‘Drawing‘) is a native file format of AutoCAD software created by AutoDesk in 1982.

It is a binary file format used for storing two- and three- dimensional design data and metadata They’re smaller files due to their binary makeup.

Although they are designed to be used in AutoCAD, users can view and edit DWG files with other programs.

IGES:

The Initial Graphics Exchange Specification (IGES) is a vendor-neutral file format that allows the digital exchange of information among computer-aided design (CAD) systems.

Using IGES, a CAD user can exchange product data models in the form of circuit diagrams, wireframe, freeform surface or solid modeling representations.

Applications supported by IGES include traditional engineering drawings, models for analysis, and other manufacturing functions.

Examples:

Used in Electronics Design

Used in Architecture Designs

JPEG vs BMP

Both are used to store digital images in raster format.

JPEG makes unidentifiable changes to image which cannot be distinguished by human eye.

It reduces file size upto 1/10th to 1/20th of original size.

JPEG can choose amount of compression in image editors like Adobe PhotoShop etc.

Differences in them is described in table below.

JPEG	BMP
It stands for Joint Photographic Experts Group	It stands for BitMap
File Extension is .jpeg or .jpg.	File Extension is >bmp.
It uses a Lossy Compression Technique	It doesn't uses a Compression Technique
File Size is Smaller Compared to BMP.	File Size is Larger Compared to JPEG.
Used in digital Cameras, storing and transmitting images over web	Used for Windows platform, image editing.

File Sizes

A file size is the measure of space a file takes on a storage medium such as a computer hard drive.

File sizes can be measured in bytes (B), kilobytes (KB), megabytes (MB), gigabytes (GB), terabyte (TB), and beyond.

In our Computer, files sizes are shown which describes how much memory they occupy.

To know the file size of a file click on the file and press Alt + Enter.

Image Formats

There are 5 main formats in which to store images.

Each of image file types has their own pros and cons. They were created for specific, yet different, purposes.

1. JPEG

JPEG stands for Joint Photographic Experts Group.

File extension is .jpegor .jpg.

"Lossy"compression format. Source file is compressed to make small file size with effect on the image quality.

JPEG can be mostly preferred while file size is chosen than image quality.

Best for:

Web images, emails, ppts etc as small in size and loads faster.

Most cameras store in JPEG format more images can be stored on card.

Bad for:

Line drawings or logos or as compression make them look jagged.

If there are images with text don't go for jpeg.

2. PNG:

Stands for Portable Network Graphics.

File extension is .png.

"Loseless" compression format.

File size is large.

Best for:

Compress images without losing quality; suitable for text documents.

Bad for:

Storage of pics on camera because of its large file size.

Also does not support animations.

3. GIF:

Stands for Graphics Interchange Format.

File extensions is .gif.

GIF files are typically small in size and are very portable.

Best for:

Web graphics and simple animations.

Mostly used on web for simple animations.

Bad for:

Photography as gif has limited colors.

Bad for printing.

4. TIFF:

Stands for Tagged Image File Format.

File extension is .tiff or .tif.

These are uncompressed and thus contain lot of detailed image data.

File size is large.

Best for:

High quality prints, professional publications, complex imagery.

Bad for:

web images as size is large takes time to load.

Most web browsers don't support tiff.

Pixels

A pixel is the smallest unit of a digital image or graphic that can be displayed and represented on a digital display device.

A pixel is also known as a picture element.

A pixel is represented by a dot or square on a computer monitor display screen.

Pixels are combined to form a complete image, video, text or any visible thing on a computer display.

The physical size of a pixel depends on how we have set the resolution of the display screen.

What is Sub-Pixel:

Each pixel actually composed of three dots a Red, Green, Blue. The three dots must converge at the same point for the image to be sharp, if not the image will be fuzzy.

Each pixel can have typically three dimensions of variability as Red, Green, Blue. Depending on the intensity of RGB different colors are produced.

Example:

Skewing

Skewing is a process of changing direction or position of image.

It turns the image at an angle and can be done in positive and negative direction.

How to Apply Skewing:

In MS Paint, open image that you want to skew. Click on Resize.

Now enter value either in Horizontal or Vertical.

It appears as below:

Aspect Ratio

Aspect ratio specifies the ratio of width to the height. Video, still pictures and the devices used to display this have the aspect ratio like 3:2, 4:3, 16:9....

The number before the colon represents the width and the number after the colon represents height.

Images on Screen with Different Aspect Ratio:

Black bars appear when the aspect ratio of the content playing isn't matched with the aspect ratio of screen.

Depending on the type of mismatch between the picture and the display's ratio, the black bars appear in different places.

Content wider than the screen it is played on will have horizontal black bars, while content that is taller will use vertical bars.

Examples:

Resolution

Number of pixels per one square inch is called resolution

Measured by number of pixels in horizontal by number of pixels in vertical.

Units are pixels per inch.

When resolution increases, images become crisper due to a higher pixel density.

In fact, text and images may also become smaller because more pixels per square inch are being displayed.

For example, going from just 800x600 to 1024x768 would increase the total number of pixels by 306,432. Those extra pixels are added to the screen with the same amount of text, thus making the text appear smaller.

When resolution decreases text should appear bigger, images are not as crisp, and performance requirements go down.

If two different sized screens have same resolution, image looks bigger in the wider screen, remaining everything is same.

Examples:

Most of monitors have 1920 x 1080 resolution.

Our mobile phones have resolution 720 x 1280 in common. Depending on the type of mobile, it changes.

We normally adjusts the quality stream of video in Youtube.

Operator Precedence

When several operations occur in an expression, each part is evaluated and resolved in a predetermined order called operator precedence.

Parentheses can be used to override the order of precedence and force some parts of an expression to be evaluated before other parts.

Operations within parentheses are always performed before those outside. Within parentheses, however, normal operator precedence is maintained.

When expressions contain operators from more than one category, arithmetic operators are evaluated first, comparison operators are evaluated next, and logical operators are evaluated last.

Comparison operators all have equal precedence i.e., they are evaluated in the left-to-right order in which they appear.

Arithmetic and logical operators are evaluated in the following order of precedence.

ARITHMETIC OPERATORS	COMPARISON OPERATORS	LOGICAL OPERATORS
Exponent(^)	Equality(=)	Not
Negation(-)	Inequality(<>)	And
Multiplication and Division(*,/)	Less than(<)	Or
Integer division(\)	Greater than(>)	Xor
Modulus arithmetic(Mod)	Less than or equal to (<=)	Eqv>
Addition and Subtraction(+,-)	Greater than or equal to(>=)	Imp
String Concatenation(&)	Is	&

When multiplication and division occur together in an expression, each operation is evaluated as it occurs from left to right.

Likewise, when addition and subtraction occur together in an expression, each operation is evaluated in order of appearance from left to right.

The string concatenation operator(&) is not an arithmetic operator, but in precedence it does fall after all arithmetic operators and before all comparison operators.

The Is operator is an object reference comparison operator. It does not compare objects or their values, it checks only to determine if two object references refer to the same object.

Examples: