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Arithmetic Operations: |
In almost all of our applications we need to construct arithmetic expressions using variables declared in our program and constant numbers. This is done ( as in algebra) using four different devices.
1) Unary arithmetic operators:
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Example |
Equivalent to |
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- 78.9 |
Unary minus or additive inverse |
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k++ |
k = k + 1 ( use k and then increase it by one ) |
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k-- |
k = k - 1 |
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++k |
k = k + 1 ( first increase it by one then use it ) |
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--k |
k = k - 1 |
2) Binary arithmetic operators ( operations involving two numbers):
Operator |
Effect |
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+ |
addition |
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- |
subtraction |
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* |
multiplication |
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/ |
division |
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% |
remainder after integer division |
NOTE 1: The two numbers used in a binary operation must, in general, agree in type. This is to say, both must be integers or both float or both double, etc. However the compiler uses some rules to proceed with operations of “mixed mode”. These rules may be complicated, but we must remember the following:
| int & float | both are converted to float |
| int & double | both are converted to double |
| float & double | both are converted to double |
NOTE 2: When we divide two integers the result is truncated to integer, consequently:
2 / 3 = 0
7 / 3 = 2
1 / 2 = 0
11 / 4 = 2
But,
2.0 / 3.0 = 0.666667
2.0 / 3 = 0.666667
2 / 3. = 0.666667
Writing 1 / 2 when one wants to write 0.5 is a very common mistake that many programers do. Please remember to add the period at the end of both or at least one of the integers, to avoid the truncation error.
3) Parentheses
Using parentheses we can group certain operations the way we mean to write them. For example:
cost = 7.2 + ( 4.0 / 0.5 ) will store 15.2 to the memory location named cost, but
cost = ( 7.2 + 4.0 ) / 0.5 will store 22.4 to cost .
4) Library functions
We can use several build in functions so that we can write expressions with sines, cosines, exponents, logarithms, exponentials, etc. In order to use these functions we must include the mathematics header by writing up on top of our program something like: #include<math.h>. Look at your book for a detailed description of the functions. Here we note only two:
pow( base, exponent) used to write powers, for example in order to write x5 we write POW(x,5).
exp( exponent ) used to write exponential, for example in order to write e5x we write exp(5*x)
