Expressions statements and operators 

All C programs are made up of statements, which are commands given to the computer executed in sequence.  These statements are usually written one per line, although this is not a coding requirement. C statements always end with a semicolon except for preprocessor directives.

Whitespace

Whitespace refers to characters that are used for formatting purposes. In C, this refers primarily to spaces, tabs, and newlines. The C compiler generally ignores whitespace, with a few minor exceptions. Whitespace serves the purpose of making the code more readable to programmers.

Null Statements

A null statement is a semicolon on a line that performs no action. 

Compound Statements

A compound statement or block comprises one or more statements enclosed within a bracket.{}

Although every statement in a compound statement must end with a semicolon, the compound statement itself does not end with a semicolon. Variables declared within the statement are local to that compound statement.

Operators

An operator is a symbol that tells the compiler to perform a specific mathematical or logical operation.  C operators fall into several categories: assignment operators, mathematical operators, relational operators, and logical operators.

Assignment Operator - is used to assign a value to a variable. The Assignment Operator is denoted by equal to sign. An assignment Operator is a binary operator which operates on two operands. The following table lists the assignment operators supported by the C language -

The Mathematical Operators - C’s arithmetic operator performs mathematical operations such as addition, subtraction, and multiplication on numerical values

assuming a=2 and b=1

Postfix or Prefix? - In C the increment ++ operator increases the value of a variable by 1 and the use of decrement -- operator decreases the value of a variable by 1. The operator placement has an important effect on the way the operations are evaluated

Placing the operator before the operand ie ++var causes the variable to be increased before it returns a value

Placing the operator after the operand ie var+ causes the value of the variable to be returned before it is incremented by 1

Relational Operators - checks if the values of two operands are equal. 

assuming a=2 and b=1

Logical Operators - applies standard boolean algebra operations to their operands

Assume variable A holds 2 and variable B holds 1, then −

Bitwise Operators - perform manipulations of data at the bit level. These operators also perform the shifting of bits from right to left. Bitwise operators are not applied to float or double.  The difference between logical and bitwise operators is that bitwise operators don’t return a boolean result but manipulate individual bits.

The Bitwise operators supported by the C language are listed in the following table. Assume variable A holds 50 and variable B holds 25, then −

A = 0011 0010

B = 000 11001

 
Misc Operators

? or ternary operator - Can be used to replace if-else statements

example:y = (x > 10) ? 10 : 20;

Here, y is assigned the value of 10 if x is greater than 10 and 20 if not

. ->(dot and arrow) ---- used to reference individual structures and unions.

&(ampersand) ---- returns the address of a variable. For example, &x; returns the location of the variable x in memory

*(asterisk) ---- Used to Declare and Dereference a pointer.

Operator Precedence in C++

Operator precedence is the order in which operators are evaluated in a compound expression. In C++, when the compiler encounters an expression, it must similarly analyse and determine how it should be evaluated. To assist with this, all operators are assigned a level of precedence. Those with the highest precedence are evaluated first.

Here, operators with the highest precedence appear at the top of the table, and those with the lowest appear at the bottom. Within an expression, higher precedence operators will be evaluated first.

for example

int myNumber = 20 * 50 + 25 – 25 * 25 << 2;

simplifies to 1000+25-625>>2

simplifies to 400>>2=100