An **`expression`** in C is a combination of *operands* and *operators* -- it computes a single value stored in a *variable*. The **operator** denotes the action or operation to be performed. The **operands** are the items to which we apply the operation.

An `expression` can be defined depending on the position and number of its operator and operands:
1. **Infix Expression** (operator is used *between* the operands)
```C
a = x + y
```

2. **Postfix Expression** (operator is used *after* the operands)
```C
xy+
```

3. **Prefix Expression** (operator is used *before* the operands)
```C
+xy
```

4. **Unary Expression** (*one* operator and *one* operand)
```C
x++
```

5. **Binary Expression** (*one* operator and *two* operands)
```C
x+y
```


# Types of Expression
There are six types of `expressions`. These are shown below:

## Arithmetic expression
It consists of arithmetic operators ( + , - , * , and / ) and computes values of `int, float, or double` type.


#include <stdio.h>

int main(){

  //Arithmetic Expression
  int a = (6 * 2) + 7 - 9; 
  printf("The arithmetic expression returns: %d\n", a);
  return 0;
}

 

## Relational expression 
It usually consists of comparison operators (> , < , >= , <= , === , and !== ) and computes the answer in the `bool` type, i.e., true (1) or false (0). 


#include <stdio.h>

int main(){

  //Relational Expression
  int b = 10;
  printf("The relational expression returns: %d\n", b % 2 == 0);

  return 0;
}


## Logical expression
It consists of logical operators (&&, ||, and !) and combines relational expressions to compute answers in the `bool` type. 


#include <stdio.h>

int main(){

  //Logical Expression
  int c = (7 > 9) && ( 5 <= 9);
  printf("The logical expression returns: %d\n", c);

  return 0;
}


## Conditional expression
It consists of conditional statements that return `true` if the condition is met and `false` otherwise. 



#include <stdio.h>

int main(){

  //Conditional Expression
  int d = (34 > 7) ? 1 : 0;
  printf("The conditional expression returns: %d\n", d);

  return 0;
}



## Pointer expression
It may consist of an ampersand (&) operator and returns `address` values. 


#include <stdio.h>

int main(){

  //Pointer Expression
  int e = 20; 
  int *addr = &e;
  printf("The pointer expression returns: %p\n", addr);

  return 0;
}


## Bitwise expression
It consists of [bitwise operators](https://www.educative.io/answers/what-are-bitwise-operators) ( >>, <<, ~, &, |, and ^ ) and performs operations at the bit level. 

#include <stdio.h>

int main(){

  //Bitwise Expression
  int f = 10;
  int shift = 10 >> 1;
  printf("The bitwise expression returns: %d\n", shift);

  return 0;
}

What are expressions in C?

Expressions in C combine operands and operators to compute values, including arithmetic, relational, logical, conditional, pointer, and bitwise types.