C program to calculate sum of integers in string

In this tutorial we are going to learn writing C program to calculate the sum of integers given in string. This program is not that much tough as we have to find the available integer in string and then add them to print the output.

How our program to calculate sum of integers work?

  • First we will take the string as an input from the users. Also we have one integer variable to store the sum.
  • We will iterate the string using loop and check the each character using isdigit() function.
  • If digit comes then add it into sum variable otherwise skip the steps.

C program to find sum of integers in String

#include <stdio.h>
#include <string.h>
#include <ctype.h>
int main()
  char str[256],sum=0;
  printf("C Program to sum all digits of a String\n");
  printf("Please enter a string : ");
  int len= strlen(str);
  for(int i=0; i<len; i++){
  printf("Sum of digits inside string is = %d",sum);
  return 0;


C program to calculate sum of integers in string

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