Types, Operators & Expressions

This document covers Types, Operators & Expressions in C.

In this section, we will cover the fundamental building blocks of the C programming language: data types, operators, and expressions. Understanding these concepts is crucial as they form the foundation for writing efficient and effective C programs.

Data Types in C

C provides various data types to store different kinds of values. These can be categorized into:

Primary Datatypes

Type	Size (bytes)	Description
char	1	Stores a single character
int	4	Stores whole numbers
float	4	Stores decimal numbers
double	8	Stores double-precision floating-point numbers
void	0	Represents no type (used for functions)

Example:

#include <stdio.h>
int main() {
    int a = 10;
    float b = 5.5;
    char c = 'X';
    printf("Integer: %d\n", a);
    printf("Float: %.1f\n", b);
    printf("Character: %c\n", c);
    return 0;
}

Derived Datatypes

• Arrays: Collection of elements of the same type.
• Pointers: Variables that store memory addresses.
• Structures (struct): User-defined data types that group related variables.
• Enumerations (enum): Used to assign names to integral constants.

The const Keyword (Constant Variables)

The const keyword is used to declare read-only variables, function parameters, and pointers to prevent unintended modifications.

Declaring const Variables

const int MAX_VALUE = 100;
MAX_VALUE = 50;  // ❌ Error: Cannot modify a constant variable

info

const variables must be initialized at the time of declaration. Attempting to modify them results in a compilation error.

tip

It is good practice to name const variables in UPPER_CASE.

Operators

Operators allow you to perform operations on variables and values.

Arithmetic Operators

Operator	Description	Example
+	Addition	a + b
-	Subtraction	a - b
*	Multiplication	a * b
/	Division	a / b
%	Modulus	a % b (remainder)

Example:

int sum = 10 + 5;
printf("Sum: %d", sum);

Comparison Operators

Operator	Description	Example
==	Equal to	a == b
!=	Not equal to	a != b
>	Greater than	a > b
<	Less than	a < b
>=	Greater than or equal to	a >= b
<=	Less than or equal to	a <= b

Logical Operators

Operator	Description	Example
&&	Logical AND	a > 5 && b < 10
||	Logical OR	a > 5 || b < 10
!	Logical NOT	!(a > b)

Example in an if statement

if (a > 5 && b < 10) {
    printf("Both conditions are true");
}

note

Please note that if statements will be covered in control flow.

Bitwise Operators

& (AND), | (OR), ^ (XOR), << (Left Shift), >> (Right Shift)

Used for low-level operations like setting or clearing bits.

Example:

int a = 5; // 0101 in binary
int b = 3; // 0011 in binary
printf("Bitwise AND: %d", a & b); // Output: 1 (0001 in binary)

Assignment Operators

Operator	Example	Equivalent To
=	a = 10;	Assign 10 to a
+=	a += 5;	a = a + 5;
-=	a -= 5;	a = a - 5;
*=	a *= 5;	a = a * 5;
/=	a /= 5;	a = a / 5;
%=	a %= 5;	a = a % 5;

Increment and Decrement Operators

Operator	Description	Example
++	Increment by 1	a++ or ++a
--	Decrement by 1	a-- or --a

Expressions in C

Expressions combine values, operators, and variables to produce results.

Example:

int x = (10 + 5) * 2;
printf("Result: %d", x);

Operator Precedence

• * / % > + - > == != > < > && ||
• Parentheses () overrides all precedence

Example:

int result = 5 + 3 * 2; // Output: 11
int correct = (5 + 3) * 2; // Output: 16

Type Conversions in C

Implicit Type Conversion (Type Promotion)

C automatically converts data types when needed.

int a = 5;
double b = a;  // int is promoted to double

Explicit Type Casting

float a = 5.67;
int b = (int)a;  // Explicit type conversion

Enumerations (enum)

An enumeration (enum) is a user-defined type consisting of named integer constants.

Declaring an enum

enum Day {
    SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY
};

By default, values start at 0 (SUNDAY = 0, MONDAY = 1, ...).

Assigning Custom Values

enum Status {
    SUCCESS = 1,
    FAILURE = 0,
    PENDING = -1
};

Using enum in Code

#include <stdio.h>
int main() {
    enum Day today = FRIDAY;
    printf("Today is day number %d\n", today);
    return 0;
}

Benefits of Using enum

• Improves code readability.
• Reduces the use of magic numbers.
• Groups related constants under a single type.