C – atoi() function

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

int atoi (const char * str);

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

Example program for atoi() function in C:

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

int main()
    char a[10] = "100";
    int value = atoi(a);
    printf("Value = %dn", value);
    return 0;


Value = 100


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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