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# C program to store even, odd and prime numbers into separate files

A file is a physical storage location on disk and a directory is a logical path which is used to organise the files. A file exists within a directory.

The three operations that we can perform on file are as follows −

- Open a file.
- Process file (read, write, modify).
- Save and close file.

## Program

Following is the C program to **store even, odd and prime numbers into separate files** −

#include <stdio.h> #include <stdlib.h> /* Function declarations */ int even(const int num); int prime(const int num); int main(){ FILE * fptrinput, * fptreven, * fptrodd, * fptrprime; int num, success; fptrinput = fopen("numbers.txt", "r"); fptreven = fopen("even-numbers.txt" , "w"); fptrodd = fopen("odd-numbers.txt" , "w"); fptrprime= fopen("prime-numbers.txt", "w"); if(fptrinput == NULL || fptreven == NULL || fptrodd == NULL || fptrprime == NULL){ /* Unable to open file hence exit */ printf("Unable to open file.

"); exit(EXIT_FAILURE); } /* File open success message */ printf("File opened successfully. Reading integers from file.

"); // Read an integer and store read status in success. while (fscanf(fptrinput, "%d", &num) != -1){ if (prime(num)) fprintf(fptrprime, "%d

", num); else if (even(num)) fprintf(fptreven, "%d

", num); else fprintf(fptrodd, "%d

", num); } fclose(fptrinput); fclose(fptreven); fclose(fptrodd); fclose(fptrprime); printf("Data written successfully."); return 0; } int even(const int num){ return !(num & 1); } int prime(const int num){ int i; if (num < 0) return 0; for ( i=2; i<=num/2; i++ ) { if (num % i == 0) { return 0; } } return 1; }

## Output

When the above program is executed, it produces the following result −

File opened successfully. Reading integers from file. Data written successfully.

## Explanation

Given below is an explanation for the program used to store even, odd and prime numbers into separate files −

Input file: numbers.txt file contains: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Which is open in read mode (already exists file) Separated even, odd and prime numbers in separate file after execution even-numbers.txt contains: 4 6 8 10 12 14 16 odd-numbers.txt contains: 9 15 prime-numbers.txt contains: 1 2 3 5 7 11 13 17

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