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Основи C

Understanding the sizeof Operator

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The sizeof() function is a staple in C programming. It helps determine the size (in bytes) of the specified object or type. For instance, let's see how many bytes the int data type occupies:

main.c

main.c


              
12345678

            
#include <stdio.h>

int main()
{
	printf("Size of int type: %d bytes\n", sizeof(int));
	
	return 0;
}

The int data type occupies 4 bytes.

Note
Note

Keep in mind that different compilers might allocate varying byte sizes for the same data type.

Bits

A bit is the most basic unit of data a computer uses. Every byte consists of eight bits.

bit and byte

It was collectively decided by engineers to equate one byte to 8 bits because this configuration conveniently represents decimal numbers. You've likely heard of the binary number system, which forms the foundation of computer operations.

binary

At its essence, the goal is to represent numerical values we use in our daily lives using combinations of zeros and ones. Any number can be represented as a combination of powers of two. For instance, the number 7 can be portrayed as 111, and here's the breakdown:

binary first example

The values 0 or 1 don't inherently have mathematical significance; they merely indicate a bit's state.

  • 0 – the bit is inactive;
  • 1 – the bit is active.

The number 113, in binary, appears as 01110001:

binary second example
Main.c

Main.c


              
123456789101112

            
#include <stdio.h>

int main() {
    
	printf("Size of int type: %d bytes\n", sizeof(int));

	printf("Size of char type: %d bytes\n", sizeof(char));

	printf("Size of double type: %d bytes\n", sizeof(double)); 

	return 0;
}

You can also use the sizeof() function on an array to ascertain its size:

main.c

main.c


              
12345678910

            
#include <stdio.h>

int main() {
    
	int intArray[10];

	printf("Size of int array: %d bytes\n", sizeof(intArray));

	return 0;
}

An array with 10 integer elements occupies 40 bytes, meaning each individual element consumes 4 bytes. If you divide the total array size by the size of one of its elements, you'll determine the array's element count:

main.c

main.c


              
1234567891011121314151617

            
#include <stdio.h>

int main() {
    
	int data[] = {		
            4, 8, 1, 5, 0, 123, 66, 11,
			64, 2, 7, 78, -0, 34, 23, 545,
			98, 890, 65, 32, 412, 6, 5465,
			87859, 656534, 324, 324, 456,
			356, 341, 5654, 534, 756, 12
    };
    
	printf("Elements in an array: %d\n", sizeof(data) / sizeof(int));
    //  Alternatevly you can use       `sizeof(data) / sizeof(data[0])`

	return 0;
}
question mark

Which C expression returns the number of elements in the array arr?

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