Was ist der unterschied ca-1 und ca-40

The only difference is the order of operations between the increment of the variable and the value the operator returns.

This code and its output explains the the difference:

#include<stdio.h>

int main(int argc, char* argv[])
{
  unsigned int i=0, a;
  printf("i initial value: %d; ", i);
  a = i++;
  printf("value returned by i++: %d, i after: %d\n", a, i);
  i=0;
  printf("i initial value: %d; ", i);
  a = ++i;
  printf(" value returned by ++i: %d, i after: %d\n",a, i);
}

The output is:

i initial value: 0; value returned by i++: 0, i after: 1
i initial value: 0;  value returned by ++i: 1, i after: 1

So basically ++i returns the value after it is incremented, while i++ return the value before it is incremented. At the end, in both cases the i will have its value incremented.

Another example:

#include<stdio.h>

int main ()
  int i=0;
  int a = i++*2;
  printf("i=0, i++*2=%d\n", a);
  i=0;
  a = ++i * 2;
  printf("i=0, ++i*2=%d\n", a);
  i=0;
  a = (++i) * 2;
  printf("i=0, (++i)*2=%d\n", a);
  i=0;
  a = (i++) * 2;
  printf("i=0, (i++)*2=%d\n", a);
  return 0;
}

Output:

i=0, i++*2=0
i=0, ++i*2=2
i=0, (++i)*2=2
i=0, (i++)*2=0

Many times there is no difference

Differences are clear when the returned value is assigned to another variable or when the increment is performed in concatenation with other operations where operations precedence is applied (i++*2 is different from ++i*2, as well as (i++)*2 and (++i)*2) in many cases they are interchangeable. A classical example is the for loop syntax:

for(int i=0; i<10; i++)

has the same effect of

for(int i=0; i<10; ++i)

Efficiency

Pre-increment is always at least as efficient as post-increment: in fact post-increment usually involves keeping a copy of the previous value around and might add a little extra code.

As others have suggested, due to compiler optimisations many times they are equally efficient, probably a for loop lies within these cases.

Rule to remember

To not make any confusion between the two operators I adopted this rule:

Associate the position of the operator ++ with respect to the variable i to the order of the ++ operation with respect to the assignment

Said in other words:

• ++ before i means incrementation must be carried out before assignment;
• ++ after i means incrementation must be carried out after assignment:

• Overview
• Definition of milligram
• Definition of international unit (IU)
• Difference between Milligram and International unit
• How to Convert Between IU & mg?
• Drugs that measured by mg and others by IU
• What does an IU measure used for?

1- Overview of Difference Between Milligram and International Unit

• In this article will show you the difference between the two units.

2- Definition of a milligram (mg):

Milligram: A unit of mass measurement in the metric system equal to a thousandth of a gram. A gram is similar to the group of one millilitre, one-thousandth of a litre, of water at 4 degrees C.

The abbreviation for milligram is mg.1

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3-Definition of international unit:

In pharmacology, International Unit (IU) is the quantity of a substance, such as a vitamin, hormone, or toxin, that produces a specified effect when tested according to an internationally accepted biological procedure. For certain substances, the IU has been identified with a weight of a particular purified form of the material; for example, one gram of vitamin A acetate contains 2.904 × 106 IU.2

The international unit differs from substance to substance; each import has international agreements. For example, 1 IU of Vit A does not equal 1 IU of Vit C.

4- Difference between Milligram and International unit

Milligram is used to measure the mass and concentration of the substance and follow the metric system.

But the international unit measures the biological effect of Vitamins or toxins.3

IU (international unit): An international unit (IU) is an internationally accepted amount of a substance.

This measure is used for fat-soluble vitamins (such as vitamins A, D and E) and certain hormones, enzymes, and biologicals (such as vaccines).

The definition of an international unit (IU) is generally arbitrary, technical, and eminently forgettable. For example, an IU of vitamin E is the specific biological activity of 0.671 milligrams of d-alpha-tocopherol. Nonetheless, most IUs are pretty handy and helpful in use as a means of standardising measures.

The International Conference for Unification of Formulae officially defines all international units.

For example:

VITAMIN A :
One milligram of beta carotene = 1667IU of Vitamin A activity.
15mg of beta carotene = 25,000IU of Vitamin A activity.

VITAMIN E :
One milligram of Vitamin E = 1.21 to 1.49IU (depending on the carrier).
400IU of d-alpha tocopherol = 268mg.

VITAMIN D:
One microgram of Vitamin D = 40 IU.
400IU of Vitamin D = 10ug.

And if their biological equivalent of the same substance may have different IU.

For example:

Vitamin A: There are two widely available preparations of vitamin A: retinol and beta carotene. The IU equivalent of vitamin A in the retinol format is 0.3 µg per 1 IU. The value for beta carotene is 0.6 µg per IU. If the RDA for vitamin A as a retinol preparation is 3,000 IU, the equivalent in micrograms is 900 µg. Converted to milligrams, this amount equals 0.9 mg.

Vitamin E: Vitamin E is available in two formats: d-alpha-tocopherol, a natural source, and dl-alpha-tocopherol, a synthetic source. One IU of d-alpha-tocopherol equals 0.67 mg. Converted to micrograms, it equals 670 µg. The dl-alpha-tocopherol formulation contains 0.9 mg of vitamin E per IU. In micrograms, that is equivalent to 900 µg. The RDA for an adult is 22.4 IU of the natural version and 33.3 IU of the synthetic version, or about 15 mg and 30 mg.

Vitamin D: The most commonly available vitamin D preparation is vitamin D3 or cholecalciferol. 40 IU of vitamin D equals one µg, which can be converted to 0.001 mg. The RDA for an adult range from 600-800 IU. In micrograms, that would be 15 to 20 µg. Using milligrams changes the value range to 0.015-0.020 mg.5

5- How to Convert Between IU & mg?

Each IU Vitamin has its specific mass of millimetre, which differ from one vitamin to another, and to convert from IU to Mg, you must know the converting value.

• Vitamin A: 1 IU is the biological equivalent of 0.3 mcg retinol or 0.6 mcg beta-carotene
• Vitamin C: 1 IU is 50 mcg L-ascorbic acid
• Vitamin D: 1 IU is the biological equivalent of 0.025 mcg cholecalciferol or ergocalciferol
• Vitamin E: 1 IU is the biological equivalent of about 0.67 mg d-alpha-tocopherol or 0.9 mg of dl-alpha-tocopherol. 4

Example conversion

Let’s say I have a soft gel capsule containing 500 IU of Vitamin A as retinol. To convert this to mcg, using the information above, I would multiply it by 0.3:

500 × 0.3 = 150mcg.

Conversely, if the soft gel capsule was described as ‘150mcg of Vitamin A as retinol’ and I wanted to convert to IU, I would divide it by 0.3.

150 ÷ 0.3 = 500 IU.

6- Drugs that measured by mg and others by IU

• Most drugs measured by Mg and gm, even with different dosage forms such as tablets, suspension, or syrup, use mg/ml.
• For example, antibiotics such as Amoxicillin – Flucloxacillin – ceftriaxone – cefotaxime, and all Cephalosporins – metronidazole
• Most OTC drugs measured by using mg: as Paracetamol – aspirin – Pantoprazole – omeprazole
• There are many drugs measured using IU

For example, Insulin and another hormone as oxytocin

Penicillin as Benzathine penicillin G measured by IU.

Many blood drugs such as coagulation factor VIII and erythropoietin, and Heparin

7- What does an IU measure use for?

IU is used in the measurement of vitamins such as vitamins A and B, Vitamin D and Vitamin E and their bio-equivalent substances, also enzymes of the human body in biological Assay, and hormone as oxytocin and insulin and vaccines.

8- What Does IU Stand for in Vitamins?

• So, what does IU mean on vitamin labels?
• When it comes to vitamins and minerals, IU stands for the same thing: international unit.
• The IU of a vitamin tells you how much that vitamin is going to make a difference in your body.
• IU measures how specific forms of vitamins will react in your body differently.
• For example, vitamin D is cholecalciferol (vitamin D3) and ergocalciferol (vitamin D2).
• Vitamin D3 (cholecalciferol) will have a different effect on the body than ergocalciferol.
• Likewise, vitamin A is available as retinol or beta-carotene, while vitamin E comes as alpha-tocopherol or dl-alpha-tocopherol. Each one of these fat-soluble vitamins has a different level of potency or biological activity in the body. Therefore, we have to measure vitamin levels with the standard unit of measurement, the IU.

What Does 5,000 IU Stand For?

• 5,000 IU does not tell you the amount based on mass.
• In fact, the IU does not measure mass or volume.
• Remember, each vitamin supplement has its level of biological effectiveness. The IU measures the point rather than the weight or amount.
• Let’s think about an example. 5,000 mg of vitamin D3 will affect the body differently from 5,000 mg of beta-carotene.
• These measurements don’t mean anything in terms of effectiveness, so we need to measure the effectiveness of each vitamin through a standardised measurement like the IU.
• 5,000 IU of Vitamin D3 is a standard daily amount of vitamin D3, especially for women with a slightly low vitamin D level.
• On the other hand, 5,000 IUs of beta-carotene is too much of the vitamin.
• In fact, this much vitamin A can leave someone prone to fractures.

Is IU the Same as MG or MCG?

• IU is not the same as mg or mcg. To refresh, IU stands for the international unit, mg stands for milligrams, and mcg stands for micrograms.
• Each one of these units of measurement stands on its own. The difference between all of these units is crucial to understand.
• IU doesn’t measure mass or volume; during mg and mcg, measure mass. While both measure weight, mg is 1,000 times more than mcg.
• When reading the vitamin label, you must read carefully to ensure you get the necessary dosage.
• Unfortunately, some vitamin labels use IUs while others use mg and mcg. You may need to do a little math in the pharmacy aisle.
• Or, you can cross your fingers in the hope that the back of the bottle tells you the weight and IU values.
• If converting from IU to weight, you must divide by the conversion factor.
• However, you must multiply by the conversion factor if converting from weight to IU.
• Since each vitamin has its potency and biological effectiveness, each kind of vitamin has its conversion factor.

Is 1,000 IU the Same as 1,000 MG?

• 1,000 IU is not the same as 1,000 mg.
• As of now, no vitamin or mineral has a conversion factor equal to one.
• Therefore, there is no case where these two values could equal one another.

In Conclusion:

• All drugs must have a specific concentration to identify and control the biological effect.
• Most drugs have a milligram (mg) concentration unit or gram (g).
• Still, different classes of medications are biological drugs, and an international team measures some vitamin concentrations.