Instructions and operators

Expressions

• Simple expressions:

  • Variable: m

  • Constant: 4

• Composed expressions:

  • Arithmetic operators precedence

    1. Post-increase/Post-decrease ➡️ e.g.: i++, i--

    2. Pre-increase/Pre-decrease ➡️ e.g.: ++i, --i

    3. * / % ➡️ e.g.: i*2, i/2, i%2

    4. + - ➡️ e.g.: i+1, i-1

    5. = ➡️ e.g.: i=1

    These operators have Side Effect on the operands (they can modify their values).

  • Relational

    • Comparison ➡️ < <= > >=

    • Equality ➡️ =

    • Inequality ➡️ !=

  • Logical

    • NOT ➡️ !

    • OR ➡️ ||

    • AND ➡️ &&

    These operators have Lazy evalutation:

    • expr1 && expr2: if expr1 is false, expr2 is not evaluated ➡️ returns false

    • expr1 || expr2: if expr1 is true, expr2 is not evaluated ➡️ returns true

  • Bitwise applicable only to two data types (int and char) and all the other derivated types (short int, unsigned int, long int, unsigned char)

Operator	Operator name	Notes
~x	Bitwise Complement
x ^ y	AND
x | y	OR
x ^ y	XOR
x >> n	Right SHIFT (by n bits)	Add 1s on the left
x << n	Left SHIFT (by n bits)	Add 0s on the right

L-value

Modifiable entities and variable:

• on the left of the assignment operator (=)

• they should not be:

  • constants

  • results of expressions (m+n = 0;)

Instruction (Expression Statement)

Expression with Side Effect followed by ;.

Example: The following expression is not read by the compiler (the same happens for the comments):

i+4;

because the previous instruction has not side effect.