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Data Types in C

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Categories of Data Types

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Primitive Data Types

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Integer (int)

• Stores whole numbers (positive, negative, or zero)
• Can be signed (default) or unsigned
• Size: 4 bytes
• Range (signed): −2,147,483,648 to 2,147,483,647
• Range (unsigned): 0 to 4,294,967,295

• Signed: min = −2^(n−1), max = 2^(n−1) − 1
• Unsigned: min = 0, max = 2^n − 1

#include <stdio.h>
int main() {
    int num = 2147483648;  // exceeds max signed int
    printf("%d", num);
    return 0;
}
// Output: -2147483648  (wraps around)

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Character (char)

• Stores a single character enclosed in single quotes: 'A', 'z', '3'
• Internally stored as its ASCII value (an integer)
• Size: 1 byte
• Range (signed): −128 to 127 | Range (unsigned): 0 to 255

• Attendance: 'P' for Present, 'A' for Absent
• Voting: 'Y' for Yes, 'N' for No
• Product sizes: 'S', 'M', 'L'

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Float (float)

• Stores decimal numbers with single precision (~6–7 significant digits)
• Size: 4 bytes | Range: 1.2E−38 to 3.4E+38
• Used when decimal values are needed but high precision isn’t critical

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Double (double)

• Stores decimal numbers with double precision (~15–16 significant digits)
• Size: 8 bytes | Range: 1.7E−308 to 1.7E+308
• long double provides even higher precision (10–16 bytes)

#include <stdio.h>
int main() {
    float f  = 1.1234567890123456f;
    double d = 1.1234567890123456;
    printf("Float : %.15f\n", f);
    printf("Double: %.15lf\n", d);
    return 0;
}
// Output:
// Float : 1.123456716537476   (less accurate)
// Double: 1.123456789012346   (more accurate)

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Void (void)

• No return type: void display() — function returns nothing
• Void pointer: void *ptr — can hold address of any type
• No parameters: int main(void) — function takes no arguments

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Data Modifiers

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Non-Primitive Data Types