C - if statement introduction

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Introduction

The if keyword is used to make decisions based upon simple comparisons.

Here's the basic format: 

if(evaluation) 
{ 
      statement; 
}

The evaluation is a comparison, a mathematical operation, the result of a function or some other condition.

If the condition is true, the statements (or statement) enclosed in braces are executed; otherwise, they're skipped.

The if statement's evaluation need not be mathematical. It can be a function that returns a true or false value; for example: 

if(ready())

Any non-zero value is considered true in C. Zero is considered false. So this statement is always true: 

if(1)

And this statement is always false: 

if(0)

When only one statement belongs to an if statement, the braces are optional.

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