program 7: Use of 'if' and 'else'

The need:
     After the previous 2 programs I was asked to make the program which would ask the user to choose whether he wanted to convert temperature from degree C to degree F or vice-versa. For that I thought that there must be a 'keyword' to select an option based on some condition(if C was developed by intelligent people) and I was right. There existed a keyword 'if' for that purpose.
I had to make out how if works. This program was written just to check the use of 'if'.
 
The code:
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#include<stdio.h>
int main()
{
    int i=0;
    if(i==0)
    printf("i is equal to zero\n");
    else
    printf("i is not equal to zero\n");
    return 0;
}
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  After the success of this program I came to know only that if there are 2 possibilities upon which we have to decide accordingly(like in our case either i can be equal to 1 or cannot be, there is no other possibility), we can use 'if' with a following 'else'. In the 'if' statement the condition is given between the parenthesis. Like in our case 'i==0' is a condition which claims that value of 'i' is equal to 0 or should I say compares 'i' to 0. The functionality of 'if' is some thing like, if the condition inside the parenthesis of 'if' statement is true (in this case (i==0)) then the statement just after if is executed otherwise skipped and statement just after 'else' is executed. In our case the output is:

  i is equal to zero

 as the condition that i is equal to 0 is always true. Two worth-noting points:
    1. The statement following if has nothing to do with the condition.
    2. There may be an 'if' statement without 'else'. but there is no 'else' case without 'if'