data representation

Complete

lang
/
c

Summary

Primitive types in C

kind	type	size(bytes)	size(bits)	value range
byte	`char`	1	8
	`unsigned char`	1	8
integer	`short int`	2	16
	`unsigned short int`	2	16
	`int`	4	32
	`unsigned int`	4	32
	`long int`	8	64
	`unsigned long int`	8	64
floating-point	`float`	4	32	to
	`double`	8	64
	`long double`	16	128

may change depending on architecture, x86_64 vs 32-bit

Concept

Units

byte = 8 bits
nibble = 4 bits
word = n bytes

Capacity

bits can represent up to values
to represent values, bits are required

0 is counted as a value

Application

Sizes of different types

#include <stdio.h>

int main(void) {
	printf("Size of 'char' (in bytes): %d\n", sizeof(char));               // 1

	printf("Size of 'short int' (in bytes): %d\n", sizeof(short int));     // 2
	printf("Size of 'int' (in bytes): %d\n", sizeof(int));                 // 4
	printf("Size of 'long int' (in bytes): %d\n", sizeof(long int));       // 8
	
	printf("Size of 'float' (in bytes): %d\n", sizeof(float));             // 4
	printf("Size of 'double' (in bytes): %d\n", sizeof(double));           // 8
	printf("Size of 'long double' (in bytes): %d\n", sizeof(long double)); // 16
	
  return 0;
}

when run on a 64-bit Arch Linux

Interpretation of different types

int num = 65;
printf("num (in %%d) = %d\n", num); // prints 70
printf("num (in %%c) = %c\n", num); // prints A

char ch = 'F';
printf("ch (in %%c) = %c\n", ch); // prints F
printf("ch (in %%d) = %d\n", ch); // prints 70

char decodes/encodes the value using the ASCII convention