Question

Identify and list all the User defined Functions to be used in the system

#include <stdio.h> ///for input output functions like printf, scanf
#include <stdlib.h>
#include <conio.h>
#include <windows.h> ///for windows related functions (not important)
#include <string.h> ///string operations

/** List of Global Variable */
COORD coord = {0,0}; /// top-left corner of window

/**
function : gotoxy
@param input: x and y coordinates
@param output: moves the cursor in specified position of console
*/
void gotoxy(int x,int y)
{
coord.X = x;
coord.Y = y;
SetConsoleCursorPosition(GetStdHandle(STD_OUTPUT_HANDLE),coord);
}

/** Main function started */

int main()
{
FILE *fp, *ft; /// file pointers
char another, choice;

/** structure that represent a employee */
struct emp
{
char name[40]; ///name of employee
int age; /// age of employee
float bs; /// basic salary of employee
};

struct emp e; /// structure variable creation

char empname[40]; /// string to store name of the employee

long int recsize; /// size of each record of employee

/** open the file in binary read and write mode
* if the file EMP.DAT already exists then it open that file in read write mode
* if the file doesn't exit it simply create a new copy
*/
fp = fopen("EMP.DAT","rb+");
if(fp == NULL)
{
fp = fopen("EMP.DAT","wb+");
if(fp == NULL)
{
printf("Connot open file");
exit(1);
}
}

/// sizeo of each record i.e. size of structure variable e
recsize = sizeof(e);

/// infinite loop continues untile the break statement encounter
while(1)
{
system("cls"); ///clear the console window
gotoxy(30,10); /// move the cursor to postion 30, 10 from top-left corner
printf("1. Add Record"); /// option for add record
gotoxy(30,12);
printf("2. List Records"); /// option for showing existing record
gotoxy(30,14);
printf("3. Modify Records"); /// option for editing record
gotoxy(30,16);
printf("4. Delete Records"); /// option for deleting record
gotoxy(30,18);
printf("5. Exit"); /// exit from the program
gotoxy(30,20);
printf("Your Choice: "); /// enter the choice 1, 2, 3, 4, 5
fflush(stdin); /// flush the input buffer
choice = getche(); /// get the input from keyboard
switch(choice)
{
case '1': /// if user press 1
system("cls");
fseek(fp,0,SEEK_END); /// search the file and move cursor to end of the file
/// here 0 indicates moving 0 distance from the end of the file

another = 'y';
while(another == 'y') /// if user want to add another record
{
printf("\nEnter name: ");
scanf("%s",e.name);
printf("\nEnter age: ");
scanf("%d", &e.age);
printf("\nEnter basic salary: ");
scanf("%f", &e.bs);

fwrite(&e,recsize,1,fp); /// write the record in the file

printf("\nAdd another record(y/n) ");
fflush(stdin);
another = getche();
}
break;
case '2':
system("cls");
rewind(fp); ///this moves file cursor to start of the file
while(fread(&e,recsize,1,fp)==1) /// read the file and fetch the record one record per fetch
{
printf("\n%s %d %.2f",e.name,e.age,e.bs); /// print the name, age and basic salary
}
getch();
break;

case '3': /// if user press 3 then do editing existing record
system("cls");
another = 'y';
while(another == 'y')
{
printf("Enter the employee name to modify: ");
scanf("%s", empname);
rewind(fp);
while(fread(&e,recsize,1,fp)==1) /// fetch all record from file
{
if(strcmp(e.name,empname) == 0) ///if entered name matches with that in file
{
printf("\nEnter new name,age and bs: ");
scanf("%s%d%f",e.name,&e.age,&e.bs);
fseek(fp,-recsize,SEEK_CUR); /// move the cursor 1 step back from current position
fwrite(&e,recsize,1,fp); /// override the record
break;
}
}
printf("\nModify another record(y/n)");
fflush(stdin);
another = getche();
}
break;
case '4':
system("cls");
another = 'y';
while(another == 'y')
{
printf("\nEnter name of employee to delete: ");
scanf("%s",empname);
ft = fopen("Temp.dat","wb"); /// create a intermediate file for temporary storage
rewind(fp); /// move record to starting of file
while(fread(&e,recsize,1,fp) == 1) /// read all records from file
{
if(strcmp(e.name,empname) != 0) /// if the entered record match
{
fwrite(&e,recsize,1,ft); /// move all records except the one that is to be deleted to temp file
}
}
fclose(fp);
fclose(ft);
remove("EMP.DAT"); /// remove the orginal file
rename("Temp.dat","EMP.DAT"); /// rename the temp file to original file name
fp = fopen("EMP.DAT", "rb+");
printf("Delete another record(y/n)");
fflush(stdin);
another = getche();
}
break;
case '5':
fclose(fp); /// close the file
exit(0); /// exit from the program
}
}
return 0;
}

Answer 1

note:- I have explained each and everything along with code, not in comment mode so don't directly run it on the compiler. run your original code on the compiler.

in this program, we are just making a simple record storing the program, which will store all records.
let see one by one:-
we can divide our program in four-part
1. Write record for writing a new record
2. Display record for displaying all record
3. Modify Record for modifying the old stored record
4. Delete record for delete our stored record

for implement our whole program we need some header file
below ara some headers
#include <stdio.h> //for standered input output functions like printf, scanf and file handling
#include <stdlib.h> // standered Libraryies and storege we use it like bat extension and file handler
#include <conio.h>
#include <windows.h> ///for windows related functions like space skipping using goto function we will see furthure
#include <string.h> ///string operations

it' s Global Variable use to indicate or start our cursure from located cell

COORD coord = {0,0}; // top-left corner of window indecting

below function just move our cursor into give or silicing cell with the help of gotoxy Imagin loke 2d place and we are moving like a pencile at the paper.

void gotoxy(int x,int y)
{
coord.X = x;   
coord.Y = y;
SetConsoleCursorPosition(GetStdHandle(STD_OUTPUT_HANDLE),coord);
}

/** Main function started */

int main()
{
FILE *fp, *ft; /// file pointers and file indicate as file handler and ft and fp is file pointer as object
char another, choice;

/** structure that represent a employee */
struct emp
{
char name[40]; ///name of employee
int age; /// age of employee
float bs; /// basic salary of employee
};

struct emp e; /// structure variable creation

char empname[40]; /// string to store name of the employee

long int recsize; /// size of each record of employee

* if the file EMP.DAT already exists then it open that file in read write mode

fp = fopen("EMP.DAT","rb+"); // open the file in binary read and write mode
if(fp == NULL)
{
fp = fopen("EMP.DAT","wb+"); // if the file doesn't exit it simply create a new copy wb menas wtitten binary mode
if(fp == NULL)
{
printf("Connot open file"); //if file is not created or not exist.
exit(1); simple close program ans return to main 1.
}
}

recsize = sizeof(e); /// sizeo of each record i.e. size of structure variable e because e is object that store all stodrage

/// infinite loop continues untile the break statement encounter
while(1)
{
system("cls"); ///clear the console window
gotoxy(30,10); /// move the cursor to postion 30, 10 from top-left corner
printf("1. Add Record"); /// option for add record
gotoxy(30,12);
printf("2. List Records"); /// option for showing existing record
gotoxy(30,14);
printf("3. Modify Records"); /// option for editing record
gotoxy(30,16);
printf("4. Delete Records"); /// option for deleting record
gotoxy(30,18);
printf("5. Exit"); /// exit from the program
gotoxy(30,20);
printf("Your Choice: "); /// enter the choice 1, 2, 3, 4, 5
fflush(stdin); /// flush the input buffer

here we decleare on variable for choice making it will run untill we will not give 0(boolean true=0 and false means 0) to while

get the input from keyboard

choice = getche();
switch(choice)
{
case '1':
if user press 1 then this program will execute

system("cls");
fseek(fp,0,SEEK_END);

in fseek file we have fp as object of file handler class(file)
here 0 indicates moving 0 distance from the end of the file
another = 'y'; by defult value is yes Or 1

while(another == 'y') /// if user want to add another record
{
printf("\nEnter name: ");
scanf("%s",e.name);
printf("\nEnter age: ");
scanf("%d", &e.age);
printf("\nEnter basic salary: ");
scanf("%f", &e.bs);

in above printf is just printing our commend which is written inside printf and scanf is taking input in varibable .And below using fwrite function we are writting our data to our EMP.bat file using addresser(onject)) e
and we can access that variable using dot operrator like e.name;

fwrite(&e,recsize,1,fp); /// write the record in the file

when we want to store our data at single storke without pressing enter button then us just use fflush function it's defind insde window header and fush register store caches.

printf("\nAdd another record(y/n) ");
fflush(stdin);
another = getche();
}
break;

in this case 2 decision we are just simple displaying our store data in Emp.bat file

case '2':
system("cls");
rewind(fp); ///this moves file cursor to start of the file
while(fread(&e,recsize,1,fp)==1) /// read the file and fetch the record one record per fetch
{
printf("\n%s %d %.2f",e.name,e.age,e.bs); /// print the name, age and basic salary
}
getch();
break;

in case 3 we gonna modify our data in case any error occurs.

case '3': /// if user press 3 then do editing existing record
system("cls");
another = 'y'; // it;s as it is previous command like decisiion making as eariler i explain.
while(another == 'y')
{
printf("Enter the employee name to modify: "); // just enter name which one record you want ot modify.
scanf("%s", empname);
rewind(fp);
while(fread(&e,recsize,1,fp)==1) /// fetch all record from file
{
if(strcmp(e.name,empname) == 0) ///if entered name matches with that in file
{
printf("\nEnter new name,age and bs: "); // overwritting at that location
scanf("%s%d%f",e.name,&e.age,&e.bs);
fseek(fp,-recsize,SEEK_CUR); /// move the cursor 1 step back from current position
fwrite(&e,recsize,1,fp); /// override the record
break;
}
}
printf("\nModify another record(y/n)");
fflush(stdin);   
another = getche();
}
break;

this case is permanatly delete our record from our data base.
case '4':
system("cls");
another = 'y';
while(another == 'y')
{
printf("\nEnter name of employee to delete: "); //authentication for simply deleteing the record you have to specify which recird do wnat delete that is locate by name so enter name
scanf("%s",empname);
ft = fopen("Temp.dat","wb"); /// create a intermediate file for temporary storage
rewind(fp); /// move record to starting of file
while(fread(&e,recsize,1,fp) == 1) /// read all records from file
{
if(strcmp(e.name,empname) != 0) /// if the entered record match
{
fwrite(&e,recsize,1,ft); /// move all records except the one that is to be deleted to temp file
}
}
fclose(fp);
fclose(ft);
remove("EMP.DAT"); /// remove the orginal file
rename("Temp.dat","EMP.DAT"); /// rename the temp file to original file name
fp = fopen("EMP.DAT", "rb+");
printf("Delete another record(y/n)");
fflush(stdin);
another = getche();
}
break;

case 5 just declreade for exit from that fucntion ....
case '5':
fclose(fp); /// close the file
exit(0); /// exit from the program
}
}
return 0;
}

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