C Basics

C Functions

C Structures

C Standard Libraries

C Advanced

C File Handling

C Errors

C Best Practices

C Data Types

❮ Previous Next ❯

C Data Types: Understanding Memory

In C, variables must be declared with a specific data type. The data type tells the compiler how much memory to allocate for the variable and what kind of values it can securely hold.

Choosing the right data type is crucial for memory efficiency and ensuring your program behaves correctly. C provides several basic (built-in) data types.

1. Basic Data Types

Here are the most common basic data types used in C:

Data Type Description Size (typical) Example Format Specifier
int Stores whole numbers (integers), without decimals. 4 bytes int age = 25; %d or %i
float Stores fractional numbers containing a decimal point. Sufficient for storing 6-7 decimal digits. 4 bytes float pi = 3.14f; %f
double Stores fractional numbers containing a decimal point. Sufficient for storing 15 decimal digits. 8 bytes double precisePi = 3.1415926535; %lf
char Stores a single character, letter, number, or ASCII value. Enclosed in single quotes. 1 byte char initial = 'A'; %c

2. Integer Types (int)

The int data type is used to store positive and negative whole numbers.

Integer Example

#include <stdio.h>


int main() {
  int items = 50;
  int negativeTemp = -15;


  printf("Number of items: %d\n", items);
  printf("Temperature is: %d\n", negativeTemp);


  return 0;
}

Size Modifiers

You can modify the int type to optimize memory usage if you know the exact range of values your variable will hold:

3. Floating-Point Types (float and double)

Use float or double when you need to store numbers with decimals.

A float offers single precision, while a double provides double precision. If you need highly accurate calculations (like scientific data or financial applications), double is the preferred choice, although it takes up twice as much memory.

Floating-Point Example

#include <stdio.h>


int main() {
  float myFloat = 9.99f;
  double myDouble = 19.99;


  // Notice the format specifiers: %f for float, %lf for double
  printf("Float value: %f\n", myFloat);
  printf("Double value: %lf\n", myDouble);


  return 0;
}

Note: It's a common practice to append an 'f' to a float literal (e.g., `3.14f`). If you omit the 'f', the compiler might treat the literal as a double by default.

4. Character Type (char)

The char data type is used to store a single character. The character must be surrounded by single quotes, like 'A' or 'c'.

Under the hood, C stores characters as integer values based on the ASCII table. For example, the character 'A' is stored as the number 65.

Exercise

?

Which format specifier is used to print a `double` variable?

❮ Previous Next ❯