Question

4. Write a program marks.c which consists of a main function and three other functions called. readmarks , changemarks (, and writemarks() The program begins by calling the function readmarks () to read the input file marksin. txt which consists of a series of lines containing a student ID number (an integer) and a numeric mark (a float). Once the ID numbers and marks have been read into arrays (by readmarks () the main program asks if the user wants to adjust a mark. If so, the user enters an ID number and the new mark. The main then calls the function changemarks () to change the mark associated with the provided student ID. The main then asks the user if they want to adjust another mark, and so on, until the user enters a student ID number of 0. Finallly, the main calls the function writemarks() to write the marks out to a file called marksout.txt. You may assume that the input file will consist of no more than 20 marks. In detail, your functions should perform the following: main: opens the input file marksin.txt and the output file marksout.txt and then calls readmarks , passing it the input file pointer, to read the IDs and marks into two arrays Once the arrays have been read, the main then prompts the user to enter a student ID and the revised mark, calls changemark () to revise the mark, and repeats these steps until the user enters a student ID number of 0. If changemark() cannot find the student ID in the list of possible IDs, the main should print out an error message, then prompt for the next student ID and revised mark. The user quits revising marks by entering the student ID number of 0 Finally, the main calls writemarks() (passing it the output file pointer) to write the revised marks to a file readmarks): takes a file pointer and the arrays as arguments and reads the student IDs and marks into arrays id and marks. The function must also return the number of marks read changemarks ): this function should take 5 values as arguments: 1) the number of marks read, 2) the ID array 3) the marks arrays, 4) the ID number of the student whose mark is to be revised, and 5) the revised mark Assignment 9 3 The function should then revise the mark of the student with the ID specified in the 4th argument. If the function cannot find the specified student ID in the ID array, it should return 0. Otherwise the function should change the mark and return 1. (NOTE: if this function returns 0, the main should report "That student is not in the marks list".) writemarks (): this function should take as arguments a file pointer, the number of marks, the ID array, and the marks array, and write the revised marks out to the output file in the same format as the input file (an ID number followed by the mark on each line). For marking purposes, change the marks of the students with the ID numbers of 2315 and 2929 to 72 and 66, respectively

Kindly solve this using C PROGRAMMING ONLY.

Answer 1

// C program to read a file containing student id and marks and output the updated details to output file
#include <stdio.h>
#include <stdlib.h>
# define MAX 20 // maximum number of students in file

// function declaration
int readmarks(FILE *fp, int studentID[], float marks[]);
int changemarks(int studentID[], float marks[], int size, int id, float mark);
void writemarks(FILE *fp, int studentID[], float marks[], int size);

int main(void) {

   int studentID[MAX]; // array to store student id
   float marks[MAX]; // array to store student marks
   int size; // number of students read
   int id;
   float mark;

   // open the input file
   FILE *fp = fopen("marksin.txt","r");
   // if input file can be opened
   if(fp != NULL)
   {
       size = readmarks(fp, studentID, marks); // call readmarks to read the data from file and return the number of records read
       fclose(fp); // close the input file
       // loop that continues till the user wants
       do
       {
           // input the student id whise marks is to be updated
           printf("Enter student id whose marks is to be updated (0 to exit) : ");
           fflush(stdout);
           scanf("%d",&id);
           if(id == 0) // check if user wants to exit
               break;
           // input the updated marks
           printf("Enter updated marks : ");
           fflush(stdout);
           scanf("%f",&mark);
           // call changemarks to update and return the outcome of the operation
           int result = changemarks(studentID, marks,size, id,mark);
           if(result == 0) // if operation is not successful
               printf("That student is not in the marks list\n");
       }while(1);

       // open the output file
       fp = fopen("marksout.txt","w");
       // call writemarks to output the details to output file
       writemarks(fp,studentID, marks, size);
       fclose(fp); // close the output file

   }else
       printf("\nUnable to open file : marksin.txt");
   return EXIT_SUCCESS;
}

// function to read student id and marks in arrays and return the number of records read
int readmarks(FILE *fp, int studentID[], float marks[])
{
   int count = 0;
   // loop till end of file
   while((!feof(fp)) && (count < MAX))
   {
       fscanf(fp,"%d %f",&studentID[count],&marks[count]); // read a record
       count++; // increment the count
   }

   return count; // return the count
}

// function to update the marks of student with id to mark
int changemarks(int studentID[], float marks[], int size, int id, float mark)
{
   // loop over the array
   for(int i=0;i<size;i++)
   {
       if(studentID[i] == id) // if id is present,update the marks
       {
           marks[i] = mark;
           return 1; // successful
       }
   }

   return 0; // student id doesn't exist
}

// function to output the data student ID and marks to output file in the same format as input file
void writemarks(FILE *fp, int studentID[], float marks[], int size)
{
   if(size > 0) // if number of records > 0
   {
       // loop over the array
       for(int i=0;i<size;i++)
       {
           if(i == size-1) // if last record, then don't add new line
           {
               fprintf(fp,"%d %f",studentID[i],marks[i]);
           }else // else add a new line
               fprintf(fp,"%d %f\n",studentID[i],marks[i]);
       }
   }
}
//end of program

Output:

Input file:

| 11234467 2165775.5 32315 80 | 42299 85 58896 58

Console:

Enter student id whose marks is to be updated (0 to exit) : 2315 Enter updated marks : 72 Enter student id whose marks is to be updated (0 to exit) : 2929 Enter updated marks : 66 That student is not in the marks list Enter student id whose marks is to be updated (0 to exit) : 0

Output file:

11234 67.000000 2165775.500000 32315 72.000000 42299 85.000000 | 58896 50.000000