String to Integer Conversion.c

// C Program to convert string
// into integer using for loop
#include <stdio.h>
#include <string.h>

int main()
{
	char* str = "4213\0";
	int num = 0;

	// converting string to number
	for (int i = 0; str[i] != '\0'; i++) {
		num = num * 10 + (str[i] - 48);
        #num = 0 * 10 + (52 - 48) = 0 + 4 = 4
        #num = 4 * 10 + (50 - 48) = 40 + 2 = 42
        #num = 42 * 10 + (49 - 48) = 420 + 1 = 421 
        #num = 421 * 10 + (51 - 48) = 4210 + 3 = 4213
	}

	// at this point num contains the converted number
	printf("%d\n", num);
	return 0;
}