Know what defines a legal variable name in C.

Understand how the modulus operator works in simple cases (i.e., with positive operands).

Understand how logical expressions work.  What evaluates to "true" or "false"?  What is the numerical value of an expression that evaluates to "true" or "false"?

Understand the meaning of and difference between prefix and postfix versions of the increment and decrement operators.

Understand how conditional expressions are evaluated.  (Are all parts of a conditional expression always evaluated?)

Understand the basics of type conversion, especially between common type pairs, such as int and char, and int and float.

What happens if you try to pass a value of the wrong type in a function call?

Be able to understand and use the ternary operator.

You will need to be familiar with the binary representation of numbers.  (You can reasonably be expected to handle numbers from 0 to 256.)

Understand the use of bitwise operators.

What is the largest number that can be represented in a char?  What happens if you attempt to store a larger number in a char?