Newer processor designs often include all the instructions of a predecessor and may add additional instructions. Sometimes, a newer design will discontinue or alter the meaning of an instruction code (typically because it is needed for new purposes), affecting code compatibility; even nearly completely compatible processors may show slightly different behavior for some instructions, but this is rarely a problem.
Systems may also differ in other details, such as memory arrangement, operating systems, or peripheral devices. Because a program normally relies on such factors, different systems will typically not run the same machine code, even when the same type of processor is used.
Most instructions have one or more opcode fields. They specify the basic instruction type. Other fields may give the type of the operands, the addressing mode, and so on. There may also be special instructions that are contained in the opcode itself. These instructions are called "immediates".
Processor designs can be different in other ways. Different instructions can have different lengths. Also, they can have the same length. Having all instructions have the same length can simplify the design.
The MIPS architecture has instructions which are 32 bits long. This section has examples of code. The general type of instruction is in the "op" (operation) field. It is the highest 6 bits. J-type (jump) and I-type (immediate) instructions are fully given by "op". R-type (register) instructions include the field "funct". It determines the exact operation of the code. The fields used in these types are:
"rs", "rt", and "rd" indicate register operands. "shamt" gives a shift amount. The "address" or "immediate" fields contain an operand directly.
Example: add the registers 1 and 2. Place the result in register 6. It is encoded:
Load a value into register 8. Take it from the memory cell 68 cells after the location listed in register 3:
Jump to the address 1024:
Area
Area is the amount of space a two dimensional (flat) surface takes up. It is useful because it is how much of a material is needed to make a hollow container. Area is the amount of surface covered by a close object or shape.
Small areas can be measured in square centimetre and large areas in square kilometre. The area of a planar figure is often written as formula_1. Areas of regular shapes such as square, rectangle, triangle and circle can be calculated through formulas. The area of an irregular shape can be approximated through grid or graph paper.
One can use different formulas to find the area of different shapes. For example:
The area of a flat object is related to the surface area and volume of a three-dimensional object.
The area under a curve can be found using integration, a concept from calculus.
Some units used to measure area are square foot, square mile, square metre and square kilometre.
Air space
Air space is the area of the air that is controlled by a country or organisation. You have to have the permission of the controller to enter their air space in an airplane. The air traffic controllers make sure the planes go in the right place and do not hit each other or something else. Some countries are very protective of their air space.
Swamp cooler
Swamp coolers are simple type of air conditioning device that can cool a room of a house or a car by using the cooling effect of the evaporation of water. Swamp coolers can cool the air temperature in a small space by drawing the air through wet pads (some are made of aspen wood) using an electric fan.
Swamp coolers work best in dry climates such as the American Southwest and the American South. They are usually much cheaper to buy and operate than refrigerated air-conditioning devices.
This type of air conditioner was first used thousands of years ago in ancient Iran
Saskatoon
Saskatoon is a city in Saskatchewan, Canada. Saskatoon is the biggest city in Saskatchewan. Saskatoon, though, is not the capital of Saskatchewan. Regina is the capital of Saskatchewan. The South Saskatchewan River flows through the centre of the city and many people enjoy boating, biking and walking in this area. The University of Saskatchewan is also in Saskatoon.
The name "Saskatoon" [in Cree: "sâskwatôn", "Saskatoon"] comes from the Cree inanimate noun "misâskwatômina" "saskatoon berries", which refers to the sweet, violet-coloured berry that grows in the area.
Glass rod
Glass rods are sometimes used as stirrers in laboratory environments.
Glass rods are often used to spread liquids evenly onto something. An example would be to coat glass surfaces with liquids to look at them under a microscope.
Glass rods rubbed with silk or fur were used in early demonstrations of electrical energy.
Glass rods are commonly manufactured in diameters of 3 mm, 6 mm, and 10 mm.
Glass is used for these rods because it does not react with most laboratory chemicals.
Thermometer
A thermometer is an instrument for measuring or showing temperature (how hot or cold something is). One type of thermometer is a narrow, concealed glass tube containing mercury or alcohol which extends along the tube as it expands. Another type is a digital thermometer, which uses electronics to measure temperature.
Early thermometers from the time of Galileo measured the expansion and contraction of air. After the middle 17th century many used alcohol or mercury. In the 19th century a mechanical thermometer was in invented that used a bimetallic strip to move a pointer. This kind is still popular where people like to read temperature from a distance.
A laboratory thermometer is a tool used in laboratories to measure temperature with high accuracy. It can be partially or fully immersed in the substance being measured. A laboratory thermometer is recognizable by its long stem with a silver bulb at the end. The silver color in the bulb normally indicates the presence of mercury. Mercury expands as the temperature increases, thus raising the reading, while decreasing temperatures contract the mercury, lowering the reading. Mercury-in-glass thermometers are less used in the 21st century as preference is shifted to other types of thermometers, such as digital, alcohol-filled and organic-based thermometers.
In the 20th century, the traditional clinical thermometer was a mercury-in-glass thermometer. People put the end of this in their mouth ("oral" temperature), under their arm, or in their rectum ("rectal" temperature).
It is only possible to find oral temperatures on patients who can hold the thermometer correctly in their mouth. So small children cannot use this method. It is also a problem for people with a cough or people who are vomiting. In the past it was a big problem because mercury thermometers needed a long time to measure the temperature. Today's digital thermometers are faster. If a person drinks something hot or cold, one still needs to wait before testing their oral temperature.
When measuring a person's rectal temperature, it helps to use a cream on the thermometer. Rectal thermometers are usually more reliable since they aren't as much influenced by other factors. In some countries people think it is embarrassing to use them for people older than two or three. In other countries, it is considered normal for children and adults to use rectal thermometers.
In the 1990s, people in many countries thought mercury thermometers were too risky, as mercury is dangerous if it leaks out. Today we use electronic thermometers. Sometimes thermometers with liquids are used, but not with mercury.
There are other kinds of medical thermometers: "tympanic" thermometers test the temperature of the tympanic membrane (the eardrum) with infrared; "band" thermometers test a person's temperature on the front of their head.
Week
A week is 7 days in connecting order. There are usually 52 weeks in a year.
In the English language, the days of the week are named after gods in Norse mythology, except for Saturday, which is named after a Roman god.