C Program to Read a Line From a File and Display it

#include <stdio.h>
#include <stdlib.h> // For exit() function
int main()
{
    char c[1000];
    FILE *fptr;

    if ((fptr = fopen("program.txt", "r")) == NULL)
    {
        printf("Error! opening file");
        // Program exits if file pointer returns NULL.
        exit(1);         
    }

    // reads text until newline 
    fscanf(fptr,"%[^\n]", c);

    printf("Data from the file:\n%s", c);
    fclose(fptr);
    
    return 0;
}

If the file program.txt is not found, this program prints error message.





If the file is found, the program saves the content of the file to a string c until '\n' newline is encountered.

Suppose, the program.txt file contains following text.
C programming is awesome.
I love C programming.
How are you doing?
The output of the program will be:
Data from the file: C programming is awesome.

C Program to Write a Sentence to a File

#include <stdio.h>
#include <stdlib.h>  /* For exit() function */
int main()
{
   char sentence[1000];
   FILE *fptr;

   fptr = fopen("program.txt", "w");
   if(fptr == NULL)
   {
      printf("Error!");
      exit(1);
   }
   
   printf("Enter a sentence:\n");
   gets(sentence);

   fprintf(fptr,"%s", sentence);
   fclose(fptr);

   return 0;
}

Output

Enter sentence: 
I am awesome and so are files.

C Program to Store Information Using Structures with Dynamically Memory Allocation

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

struct course
{
   int marks;
   char subject[30];
};

int main()
{
   struct course *ptr;
   int i, noOfRecords;
   printf("Enter number of records: ");
   scanf("%d", &noOfRecords);

   // Allocates the memory for noOfRecords structures with pointer ptr pointing to the base address.
   ptr = (struct course*) malloc (noOfRecords * sizeof(struct course));

   for(i = 0; i < noOfRecords; ++i)
   {
       printf("Enter name of the subject and marks respectively:\n");
       scanf("%s %d", &(ptr+i)->subject, &(ptr+i)->marks);
   }

   printf("Displaying Information:\n");

   for(i = 0; i < noOfRecords ; ++i)
       printf("%s\t%d\n", (ptr+i)->subject, (ptr+i)->marks);

   return 0;
}

Output

Enter number of records: 2
Enter name of the subject and marks respectively:
Programming
22
Enter name of the subject and marks respectively:
Structure
33

Displaying Information:
Programming      22
Structure        33

C Program to Store Information of Students Using Structure

#include <stdio.h>
struct student
{
    char name[50];
    int roll;
    float marks;
} s[10];

int main()
{
    int i;

    printf("Enter information of students:\n");

    // storing information
    for(i=0; i<10; ++i)
    {
        s[i].roll = i+1;

        printf("\nFor roll number%d,\n",s[i].roll);

        printf("Enter name: ");
        scanf("%s",s[i].name);

        printf("Enter marks: ");
        scanf("%f",&s[i].marks);

        printf("\n");
    }

    printf("Displaying Information:\n\n");
    // displaying information
    for(i=0; i<10; ++i)
    {
        printf("\nRoll number: %d\n",i+1);
        printf("Name: ");
        puts(s[i].name);
        printf("Marks: %.1f",s[i].marks);
        printf("\n");
    }
    return 0;
}

Output

Enter information of students: 

For roll number1,
Enter name: Tom
Enter marks: 98

For roll number2,
Enter name: Jerry
Enter marks: 89
.
.
.
Displaying Information:

Roll number: 1
Name: Tom
Marks: 98
.
.
.

C Program to Calculate Difference Between Two Time Periods

#include <stdio.h>
struct TIME
{
  int seconds;
  int minutes;
  int hours;
};
void differenceBetweenTimePeriod(struct TIME t1, struct TIME t2, struct TIME *diff);

int main()
{
    struct TIME startTime, stopTime, diff;

    printf("Enter start time: \n");
    printf("Enter hours, minutes and seconds respectively: ");
    scanf("%d %d %d", &startTime.hours, &startTime.minutes, &startTime.seconds);

    printf("Enter stop time: \n");
    printf("Enter hours, minutes and seconds respectively: ");
    scanf("%d %d %d", &stopTime.hours, &stopTime.minutes, &stopTime.seconds);

    // Calculate the difference between the start and stop time period.
    differenceBetweenTimePeriod(startTime, stopTime, &diff);

    printf("\nTIME DIFFERENCE: %d:%d:%d - ", startTime.hours, startTime.minutes, startTime.seconds);
    printf("%d:%d:%d ", stopTime.hours, stopTime.minutes, stopTime.seconds);
    printf("= %d:%d:%d\n", diff.hours, diff.minutes, diff.seconds);

    return 0;
}

void differenceBetweenTimePeriod(struct TIME start, struct TIME stop, struct TIME *diff)
{
    if(stop.seconds > start.seconds){
        --start.minutes;
        start.seconds += 60;
    }

    diff->seconds = start.seconds - stop.seconds;
    if(stop.minutes > start.minutes){
        --start.hours;
        start.minutes += 60;
    }

    diff->minutes = start.minutes - stop.minutes;
    diff->hours = start.hours - stop.hours;
}

Output

Enter start time:
Enter hours, minutes and seconds respectively: 12
34
55
Enter stop time:
Enter hours, minutes and seconds respectively:8
12
15

TIME DIFFERENCE: 12:34:55 - 8:12:15 = 4:22:40

C Program to Add Two Complex Numbers by Passing Structure to a Function

#include <stdio.h>
typedef struct complex
{
    float real;
    float imag;
} complex;
complex add(complex n1,complex n2);

int main()
{
    complex n1, n2, temp;

    printf("For 1st complex number \n");
    printf("Enter real and imaginary part respectively:\n");
    scanf("%f %f", &n1.real, &n1.imag);

    printf("\nFor 2nd complex number \n");
    printf("Enter real and imaginary part respectively:\n");
    scanf("%f %f", &n2.real, &n2.imag);

    temp = add(n1, n2);
    printf("Sum = %.1f + %.1fi", temp.real, temp.imag);

    return 0;
}

complex add(complex n1, complex n2)
{
      complex temp;

      temp.real = n1.real + n2.real;
      temp.imag = n1.imag + n2.imag;

      return(temp);
}

Output

For 1st complex number
Enter real and imaginary part respectively: 2.3
4.5

For 2nd complex number
Enter real and imaginary part respectively: 3.4
5
Sum = 5.7 + 9.5i

C Program to Add Two Distances (in inch-feet) System Using Structures

#include <stdio.h>

struct Distance
{
    int feet;
    float inch;
} d1, d2, sumOfDistances;

int main()
{
    printf("Enter information for 1st distance\n");
    printf("Enter feet: ");
    scanf("%d", &d1.feet);
    printf("Enter inch: ");
    scanf("%f", &d1.inch);

    printf("\nEnter information for 2nd distance\n");
    printf("Enter feet: ");
    scanf("%d", &d2.feet);
    printf("Enter inch: ");
    scanf("%f", &d2.inch);


    sumOfDistances.feet = d1.feet+d2.feet;
    sumOfDistances.inch = d1.inch+d2.inch;

    // If inch is greater than 12, changing it to feet.

    if (sumOfDistances.inch>12.0)
    {
        sumOfDistances.inch = sumOfDistances.inch-12.0;
        ++sumOfDistances.feet;
    }

    printf("\nSum of distances = %d\'-%.1f\"",sumOfDistances.feet, sumOfDistances.inch);
    return 0;
}

Output

Enter information for 1st distance
Enter feet: 23
Enter inch: 8.6

Enter information for 2nd distance
Enter feet: 34
Enter inch: 2.4

Sum of distances = 57'-11.0"