Bitmap

A bitmap (or raster graphic) is a digital image composed of a matrix of dots. When viewed at 100%, each dot corresponds to an individual pixel on a display. In a standard bitmap image, each dot can be assigned a different color. Together, these dots can be used to represent any type of rectangular picture.

There are several different bitmap file formats. The standard, uncompressed bitmap format is also known as the "BMP" format or the device independent bitmap (DIB) format. It includes a header, which defines the size of the image and the number of colors the image may contain, and a list of pixels with their corresponding colors. This simple, universal image format can be recognized on nearly all platforms, but is not very efficient, especially for large images.

Other bitmap image formats, such as JPEG, GIF, and PNG, incorporate compressionalgorithms to reduce file size. Each format uses a different type of compression, but they all represent an image as a grid of pixels. Compressed bitmaps are significantly smaller than uncompressed BMP files and can be downloaded more quickly. Therefore, most images you see on the web are compressed bitmaps.

If you zoom into a bitmap image, regardless of the file format, it will look blocky because each dot will take up more than one pixel. Therefore, bitmap images will appear blurry if they are enlarged. Vector graphics, on the other hand, are composed of paths instead of dots, and can be scaled without reducing the quality of the image.

BINARY

Binary - So Simple a Computer Can Do It

While every modern computer exchanges and processes information in the ones and zeros of binary, rather than the more cumbersome ten-digit decimal system, the idea isn't a new one.

Australia's aboriginal peoples counted by two, and many tribes of the African bush sent complex messages using drum signals at high and low pitches. Morse code, as well, uses two digits (dots and dashes) to represent the alphabet.

Gottfried Leibniz laid the modern foundation of the movement from decimal to binary as far back as 1666, while John Atanasoff, a physics professor at Iowa State College, had built a prototype binary computer by 1939.

In the meantime, Claude Shannon, Konrad Zuse and George Stibitz had been pondering away in their own corners of the world, musing on the benefits of combining binary numbers with boolean logic.

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Today, of course, and in almost every computer built since the 1950s, the binary system has replaced the decimal (which really only came about because it was handy to be able to count on your fingers) and advanced digital computer capabilities to an incredible degree.

Basically, binary simplifies information processing. Because there must always be at least two symbols for a processing system to be able to distinguish significance or purpose, binary is the smallest numbering system that can be used.

The computer's CPU need only recognise two states, on or off, but (with just a touch of Leibniz' mysticism) from this on-off, yes-no state all things flow - in the same way as a switch must always be open or closed, or an electrical flow on or off, a binary digit must always be one or zero.

If switches are then arranged along boolean guidelines, these two simple digits can create circuits capable of performing both logical and mathematical operations.

The reduction of decimal to binary does increase the length of the number, a lot, but this is more than made up for in the increase in speed, memory and utilisation.

Especially utilisation. Remember, computers aren't always dealing with pure numbers or logic. Pictures and sound must first be reduced to numerical equivalents that, in turn, have to be decoded again for the end result.

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So, how does it work?

It's not so very difficult, really. Binary numbers use the same rules as decimal - the value of any digit always depends on its position in the whole number.

It all gets down to bases. Decimal uses base ten, so that every time a number moves one position to the left in a figure, it increases by a power of ten (eg. 1, 10, 100 etc). Binary, on the other hand, uses base two, so each move to the left increases the value by a power of two (eg. 1, 2, 4 etc).

To convert from decimal to binary, or the other way around, you need only look at the figure's place in the whole number and add up it's value.

Simple.

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Binary vs decimal

Decimal 10 1 0 1 2 3 4 5 6 7 8 9 1 0

Binary 8 4 2 1 0 1 1 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1 1 0 0 0 1 0 0 1 1 0 1 0

Because binary uses base two as opposed to the decimal base ten, the numbers get larger much more quickly, but they still obey the same principles.In this case, the number ten is represented by 10(no 1s, one x 10) in decimal, and 1010 (no 1s, one x 2, no 4s, one x 8) in binary.

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Conversion

To convert a decimal number to binary, you need only keep subtracting the largest power of two. Here the decimal 200 is represented by 11001000 (one x 128, one x 64, no 32s, no 16s, one x 8, no 4s, no 2s, no 1s)

From binary to decimal is even easier - just add up the columns.

Decimal
100	10	1
2	0	0
2 x 100 + 0 + 0 = 200

Binary
128	64	32	16	8	4	2	1
1	1	0	0	1	0	0	0
1 x 128 + 1 x 64 + 0 + 0 + 1 x 8 + 0 + 0 + 0 =200

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Addition

Again, addition differs only from decimal in that it is using base two.

+ Decimal 100 10 1 2 0 0 5 0 2 5 0

+ Binary 128 64 32 16 8 4 2 1 1 1 0 0 1 0 0 0 0 0 1 1 0 0 1 0 1 1 1 1 1 0 1 0

The only trick here is to remember that it is base 2 - whereas in decimal 1 + 1 = 2 with nothing to carry into the next column, in binary, 1 + 1 still = 2, but that 2 is carried forward (as a 1, naturally).

+ Decimal 10 1 1 1 2

+ Binary 2 1 1 1 1 0