C – atol() function

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  • atol() function in C language converts string data type to long data type. Syntax for atol() function is given below.

long int atol ( const char * str );

  • “stdlib.h” header file supports all the type casting functions in C language.

Example program for atol() function in C:

#include <stdio.h>
#include <stdlib.h>

int main()
    char a[20] = "100000000000";
    long value = atol(a);
    printf("Value = %ldn", value);
    return 0;


Value = 100000000000


Other inbuilt typecasting functions in C language:

    • Typecasting functions in C language performs data type conversion from one type to another.
    • Click on each function name below for description and example programs.
S.no Typecast function Description
1 atof() Converts string to float
2 atoi() Converts string to int
3 atol() Converts string to long
4 itoa() Converts int to string
5 ltoa() Converts long to string

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