Here is source code of the C Program to create employee record and update it. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

/*
* C Program to Create Employee Record and Update it
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define size 200

struct emp
{
int id;
char *name;
}*emp1, *emp3;

void display();
void create();
void update();

FILE *fp, *fp1;
int count = 0;

void main(int argc, char **argv)
{
int i, n, ch;

printf("1] Create a Record\n");
printf("2] Display Records\n");
printf("3] Update Records\n");
printf("4] Exit");
while (1)
{
printf("\nEnter your choice : ");
scanf("%d", &ch);
switch (ch)
{
case 1:
fp = fopen(argv[1], "a");
create();
break;
case 2:
fp1 = fopen(argv[1],"rb");
display();
break;
case 3:
fp1 = fopen(argv[1], "r+");
update();
break;
case 4:
exit(0);
}
}
}

/* To create an employee record */
void create()
{
int i;
char *p;

emp1 = (struct emp *)malloc(sizeof(struct emp));
emp1->name = (char *)malloc((size)*(sizeof(char)));
printf("Enter name of employee : ");
scanf(" %[^\n]s", emp1->name);
printf("Enter emp id : ");
scanf(" %d", &emp1->id);
fwrite(&emp1->id, sizeof(emp1->id), 1, fp);
fwrite(emp1->name, size, 1, fp);
count++; // count to number of entries of records
fclose(fp);
}

/* Display the records in the file */
void display()
{
emp3=(struct emp *)malloc(1*sizeof(struct emp));
emp3->name=(char *)malloc(size*sizeof(char));
int i = 1;

if (fp1 == NULL)
printf("\nFile not opened for reading");
while (i <= count)
{
fread(&emp3->id, sizeof(emp3->id), 1, fp1);
fread(emp3->name, size, 1, fp1);
printf("\n%d %s",emp3->id,emp3->name);
i++;
}
fclose(fp1);
free(emp3->name);
free(emp3);
}

void update()
{
int id, flag = 0, i = 1;
char s[size];

if (fp1 == NULL)
{
printf("File cant be opened");
return;
}
printf("Enter employee id to update : ");
scanf("%d", &id);
emp3 = (struct emp *)malloc(1*sizeof(struct emp));
emp3->name=(char *)malloc(size*sizeof(char));
while(i<=count)
{
fread(&emp3->id, sizeof(emp3->id), 1, fp1);
fread(emp3->name,size,1,fp1);
if (id == emp3->id)
{
printf("Enter new name of emplyee to update : ");
scanf(" %[^\n]s", s);
fseek(fp1, -204L, SEEK_CUR);
fwrite(&emp3->id, sizeof(emp3->id), 1, fp1);
fwrite(s, size, 1, fp1);
flag = 1;
break;
}
i++;
}
if (flag != 1)
{
printf("No employee record found");
flag = 0;
}
fclose(fp1);
free(emp3->name); /* to free allocated memory */
free(emp3);
}


$ a.out emprec1

1] Create a Record
2] Display Records
3] Update Records
4] Exit
Enter your choice : 1
Enter name of employee : aaa
Enter emp id : 100

Enter your choice : 1
Enter name of employee : bbb
Enter emp id : 200

Enter your choice : 1
Enter name of employee : ccc
Enter emp id : 300

Enter your choice : 1
Enter name of employee : ddd
Enter emp id : 400

Enter your choice : 1
Enter name of employee : eee
Enter emp id : 500

Enter your choice : 2

100 aaa
200 bbb
300 ccc
400 ddd
500 eee
Enter your choice : 3
Enter employee id to update : 300
Enter new name of emplyee to update : cdefgh

Enter your choice : 2

100 aaa
200 bbb
300 cdefgh
400 ddd
500 eee
Enter your choice : 4