Section 9.6 Combining Multiple Logic Statements
The way to write the logical 
AND in C is with two ampersand signs: 
&&
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The way to write the logical 
OR in C is with two vertical bars: 
||
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The way to negate a condition in C is to put an exclamation mark in front of it: 
!(...)
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Investigate 9.4.
Zero is the value which C interprets as false. How could you use a logical operator so that C would interpret anything 
except zero as false, such as in an 
if statement?