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Before proceeding to the consideration of syntaxfunction "if", we define its purpose. It is known from English language lessons that "if" means "if", and from the lessons of computer science "if" (IF) is a logical function of the condition: IF condition 1 is fulfilled, then TRUE, otherwise  FALSE. Condition 1 implies some logical expression (for example, a comparison), TRUE means that the condition is true. As a result of the condition, some mathematical expression may appear.
For an understanding, let us consider an example of prices in a movie theater. It is known that most sessions in the morning hours (say, up to 12 hours) are cheaper than in the daytime (up to 22 hours), and those in turn are cheaper than evening (up to 24 hours). Since we have 3 possible conditions (up to 12, up to 20 and up to 24), then we have a branching algorithm (nested if loop):
 IF to 12, then 100 rubles., AKA
 IF up to 20, then 200 rubles.
 Otherwise 250 rubles.
 IF up to 20, then 200 rubles.
Use of this function is useful, in the first placeturn, mathematicians, accountants and financiers (for calculating wages, calculating loans, etc.). It is most simple to implement it in MS Office Excel, since "excel" is the most common spreadsheet program in the Windows operating system, and the syntax is the same for all versions (from 97 to 2012).
How to make "if" in Excel?
To use the function, you need to click the left mouse button (LMB) in the free field of the table, put the "=" sign and write "IF". "Excel" will give a popup hint in the form:
 IF (log_expression; [value_if_true]; [value_if_long]
To select this expression, click on it 2 times LMC.
The fields described in square brackets [] are optional.
Consider the example:
Let's have a warehouse of a home appliance store, and among the goods you need to find TV sets of the Russian assembly costing up to 15 000 rubles.
The table has 4 columns: the column Aname of the product, B  the producer country, C  the price for the goods, D  the marks about the desired product.
In order to fulfill our 3 conditions (TV and Russia and Up to 15,000 rubles), you need to write the following expression in the free field (D2second row of column D):
 = IF (AND (A2 = "TV"; B2 = "Russia"; C2 <15000); "+";)
Name 
a country 
Price, rub 

TV  Russia  10000  + 
fridge  Germany  10000  0 
kettle  Poland  2000  0 
fridge  Russia  18000  0 
TV  Russia  160000  0 
kettle  Russia  1000  0 
toaster  Hungary  1500  0 
TV  China  12000  0 
fridge  Russia  19000  0 
kettle  China  1800  0 
fridge  Belarus  10500  0 
toaster  China  2000  0 
kettle  China  2500  0 
TV  Russia  14800  + 
fridge  Germany  25000  0 
Knowing how the "if" function works, you can create nested loops to solve more complex tasks and multiple condition checks.