04_data_types.md

Data Types in C Programming

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Data types in C specify the type of data that a variable can hold.
They help the compiler allocate memory and interpret the data correctly.

Basic Data Types

Data Type	Size (bytes)	Format Specifier	Example Usage
int	4	%d	int age = 25;
float	4	%f	float temp = 36.6;
double	8	%lf (scanf), %f (printf)	double pi = 3.14;
char	1	%c	char grade = 'A';
char[] (string)	varies	%s	char name[20] = "John";
_Bool / bool	1	%d	_Bool flag = 1;

Note: Sizes may vary depending on system and compiler, but these are typical for most platforms.

Usage

• int: Used for whole numbers (positive, negative, zero).
• float: Used for decimal numbers with single precision.
• double: Used for decimal numbers with double precision.
• char: Used for single characters.
• char[] (string): Used for storing sequences of characters (strings).
• _Bool / bool: Used for boolean values (0 for false, 1 for true).
  To use bool, include #include <stdbool.h>.

Format Specifiers

• %d for int and bool
• %f for float and for double in printf
• %lf for double in scanf
• %c for char
• %s for strings (char[])

Important:
For double, use %f in printf and %lf in scanf:

• printf("%f", myDouble); // prints double value
• scanf("%lf", &myDouble); // reads double value

Taking Input for Different Data Types

#include <stdio.h>
#include <stdbool.h>

int main() {
    int num;
    float fnum;
    double dnum;
    char ch;
    char inputStr[10];
    bool flag;

    printf("Enter an integer: ");
    scanf("%d", &num);

    printf("Enter a float: ");
    scanf("%f", &fnum);

    printf("Enter a double: ");
    scanf("%lf", &dnum);

    printf("Enter a character: ");
    scanf(" %c", &ch); // Note the space before %c to consume any leftover newline

    printf("Enter a string: ");
    scanf("%s", inputStr); // No & needed for arrays when passing to scanf for strings

    printf("Enter a boolean (0 or 1): ");
    scanf("%d", &flag);

    printf("\nYou entered:\n");
    printf("Integer: %d\n", num);
    printf("Float: %f\n", fnum);
    printf("Double: %f\n", dnum); // use %f for double in printf
    printf("Character: %c\n", ch);
    printf("String: %s\n", inputStr);
    printf("Boolean: %d\n", flag);

    return 0;
}

Derived Data Types

• Array: Collection of elements of the same type.
  Example: int numbers[5];
• Pointer: Stores the address of another variable.
  Example: int *ptr;
• Structure: Group of variables of different types.
  Example:

  struct Person {
      char name[50];
      int age;
  };

• Union: Stores different data types in the same memory location.
  Example:

  union Data {
      int i;
      float f;
      char str[20];
  };

Data Types and Memory Organization

• Primitive data types (int, float, etc.) are stored in memory as single blocks.
• Arrays are stored as contiguous blocks (like a queue, elements are accessed in order).
• Structures are stored as a collection of blocks, one for each member.
• Unions share the same memory location for all members.
• Pointers store the memory address of another variable.

Note: Data types themselves do not behave like queues or stacks.
Queues and stacks are data structures that can be implemented using arrays, structures, or pointers.

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Choosing the correct data type is important for efficient memory usage and program correctness.

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