Write a C program to convert a string to a long integer

Approach-1:

• We use strtol() function to covert string to long integer.
• It is belongs to stdlib.h header file.
• The prototype of function is
  • long int strtol(const char *str, char **endptr, int base)
• It converts the initial part of the string in str to a long int value according to the given base, which must be between 2 and 36 inclusive, or be the special value 0.

#include<stdio.h>
#include<stdlib.h>
int main ()
{
	char s[] = "2021 1a 1101";
	char *p;
	long int a, b, c;

	a = strtol (s,&p,10);
	b = strtol (p,&p,16);
	c = strtol (p,&p,2);
	printf ("Result values : %ld, %ld, %ld\n", a, b, c);
	return 0;
}

Approach-2:

• dos.h header file providing another library function to convert given string into long type.
• The prototype of function is
  • long atol(char* s);

#include<stdio.h>
#include<dos.h>
int main()
{
	long res;
	res = atol("123456");
	printf("String \"123456\" converted to long int is %ld\n", res);
	return 0;
}