A kilobyte (kB) is a number used to measure storage space on computer hard drives or computer memory. A kilobyte originally meant 1000 bytes. Over time the meaning changed and today it is often used to mean 1024 bytes. This created some confusion as a "kilo" normally means 1000. The International Electrotechnical Commission (IEC) now defines a kilobyte as being 1000 bytes. According to the IEC, the correct name for 1,024 bytes is a kibibyte.
One thousand kilobytes make one megabyte.
Byte
A byte is a unit of measurement of the size of information on a computer or other electronic device. A single byte is usually eight bits. Some early computers used six bits for each byte. Bits are the smallest unit of storage on a computer, a single on/off value. Bytes are often represented by the capital letter B, bits by a lower case b.
A single typed character (for example, 'x' or '8') is stored in one byte. The character is held as a binary number which encodes a text character. To map each number to a character an agreed code such as EBCDIC or ASCII is needed. EBCDIC is a character encoding used mainly on mainframe computers. It uses 8 bits per byte. ASCII is another encoding that only uses seven bits. "Extended ASCII" uses 8 bits to give more types of characters, mostly used on personal computers.
The byte is the smallest useful unit of measure to show how many characters a computer (or electronics device) can hold. This is useful for things like RAM, or storage devices like USB drives and other types of Flash memory. Sending of data (for a modem or wi-fi) is usually measured in bits, not bytes.
On modern computers one byte is equal to eight bits. Some early computers used fewer bits for each byte. To tell them apart, computer scientists called an 8 bit byte an octet. In modern usage, an octet and a byte are the same.
The symbol for "byte" is "B". Sometimes a lowercase "b" is used, but this use is incorrect because "b" is actually the IEEE symbol for "bit". The IEC symbol for bit is bit. For example, "MB" means "megabyte" and "Mbit" means "megabit". The difference is important because 1 megabyte (MB) is 1,000,000 bytes, and 1 megabit (Mbit) is 1,000,000 bits or 125,000 bytes. It's easy to confuse the two, but bits are much smaller than bytes, so the symbol "b" should be used when referring to "bits" and an uppercase "B" when referring to "bytes".
For large data, byte is often used with a binary prefix:
The following terms represent even larger units of bytes, but are very rarely used:
According to the International Electrotechnical Commission (IEC), who sets many computer standards, these charts show how bytes should be referred to.
People who refer to 1 kilobyte as 1,024 bytes, for example, are technically incorrect; 1,024 bytes should be referred to as 1 kibibyte, according to the IEC. However, using 1024 for kilo and 1048576 for mega, etc. was widely practiced before the IEC standards were set in 1998. There is some confusion and mixing of terms in the marketplace. Computer memory is still referred to in powers of 2, so 1KB of memory is 1024 bytes, whereas in computer data storage powers of 10 are used, so 1KB is 1000 bytes.
When using standard metric names like "kilo-", "mega-" and "giga-", they should follow the same measure that other metric measurements use, like kilometer (1 kilometer = 1,000 meters), or gigahertz (1 gigahertz = 1,000,000,000 hertz) for example.
Since computers are very complex digital devices that are based on the binary numeral system rather than the commonly-used decimal numeral system or binary coded decimal system, there are many situations where the standard metric system does not work well, particularly with memory sizes for a computer or storage device. If a memory or storage device uses a binary number for addresses, the number of different positions to be accessed (the size of the memory) can be expressed as a power of 2, rather than a power of 10.
Subatomic particle
A subatomic particle is a particle smaller than an atom. This means it is very, very small. Like atoms and molecules, a subatomic particle is far too small to be seen with the naked eye. It is also very interesting to scientists who try to understand atoms better. The commonly studied subatomic particles are the main ones that make atoms: protons, neutrons, and electrons. The study of subatomic particles is called particle physics.
These particles are often held together within an atom by one of the four fundamental forces (gravity, electromagnetic force, strong force, or weak force). Outside of the atom the particles often move very, very quickly- near the speed of light which is very, very fast (around 300,000 kilometres per second).
Subatomic particles are divided into two groups, Baryons and Leptons.
Baryons are made of quarks while Leptons are thought to be among the smallest particles, called elementary particles. Baryons have a given Baryon number. In reactions, the Baryon number must be conserved, meaning that both the starting and ending sides of a reaction must have the same number of Baryons. Baryonic particles are made up of a combination of 3 of the six quarks, which are among the smallest particles. The six quark types are up, down (making up protons and neutrons), strange, charm, top, and bottom.
Leptons are generally much smaller than Baryons. This category includes electrons, Muons, Taus and neutrinos. Leptons are not made up of quarks and are not divisible.
For every one of these types, there is also an antiparticle. Antiparticles have the same mass as their normal counterparts, except they have the opposite electric charge. Anti-matter and matter cannot exist near each other. Whenever matter and antimatter collide, they destroy each other with a huge release of energy equivalent to E=mc, where m is the combined mass of the particles, c is the speed of light, and E is the energy produced. These collisions often take place in large particle accelerators, where the energy can be converted the other way, into matter by the same equation. This can produce many odd, often heavy (large mass) particles that exist only for a short time.
Most of the particles discovered are created by accelerating particles and colliding them against others, creating huge showers of new subatomic particles which decay extremely quickly. However, because the particles are moving close to the speed of light, the laws of special relativity become important and time dilation occurs. This means that time passes slower for the particle, and they can travel (and be measured) over a longer distance than non-relativity science would predict.
Screen
A screen can be:
Breathing
Breathing is moving air in and out of the lungs. The air going in and out is called "breath". If a person cannot breathe, they will die.
Breathing helps people do two very important things:
When a person breathes in, they bring air into their lungs. Air has oxygen in it. The oxygen goes from the lungs into the person's bloodstream. When oxygen goes into the bloodstream, extra carbon dioxide comes out and goes into the lungs. This is called gas exchange: basically, oxygen and carbon dioxide are changing places. Oxygen is now in the bloodstream, which can carry that oxygen around to every part of the body. Also, carbon dioxide is now in the lungs, where it can be breathed out.
Adults breathe about 18 times a minute, which is more than 25,000 times a day. Children breathe even faster.
A part of the brainstem called the medulla oblongata controls breathing. Groups of neurons in the medulla tell the breathing muscles when to breathe in, when to breathe faster, and when to breathe slower.
The brainstem measures how much carbon dioxide is in a person's blood. If there is too much carbon dioxide, the medulla tells the body to breathe faster. This helps the person breathe out the extra carbon dioxide. Once the amount of carbon dioxide in the blood is normal again, the medulla tells the body to breathe slower again.