Employee Database System - C
This is a program written in C to implement a employee database system. It allows you to add, edit and delete employees as well as display all registered employees in an alphabetic order.
This program implements a linked list data structure using structs as nodes and pointers. Each node is an employee which stores their name, gender, age and job description as the data. It loops through a menu indicating the options available until you quit. Adding an employee would insert them into the list in an alphabetic order, user input is validated to take in the required data for new employees. Deleting an employee will allow you to select one and their node will be removed from the list and the link or their pointer will be reassigned. Editing an employee would let you choose an employee and change their data, and re sort them in the list if necessary.
A video demonstrating the output and the code is shown below:
View the Source Code below, or view the full codebase on GitHub
1 /******************************************************************************************
2 *Student Name: Mostapha Abdelaziz
3 *Assignment Number: Assignment 2
4 *Assignment Name: Employee Database Implementation
5 *Course: C Language
6 *Source Files: main.c header.h
7 ******************************************************************************************/
8
9 #ifndef header_h
10 #define header_h
11
12 /* needed libraries */
13 #include <stdlib.h>
14 #include <string.h>
15 #include <stdio.h>
16
17 #define MAX_NAME_LENGTH 100
18 #define MAX_JOB_LENGTH 100
19
20 /* Employee structure*/
21 struct Employee
22 {
23 char name[MAX_NAME_LENGTH];
24 char gender[20];
25 int age;
26 char description[MAX_JOB_LENGTH];
27
28 /* pointers to next employee structures in the linked list*/
29 struct Employee *next;
30 };
31
32 /* function declarations */
33 void validateEmployeeDetails(struct Employee *employee);
34 void printEmployees(struct Employee *employee);
35 int validateInt(char *input);
36 int printMenu();
37 void addSortEmployee(struct Employee *head, struct Employee *employee, int empCount);
38 void verifyString(char *string);
39 int findEmployee(struct Employee *head, char *name, int age);
40 void editEmployee(struct Employee *employee);
41 int accessEmployee(struct Employee *head, struct Employee *employee, int empCount, int option);
42
43 #endif
44
1 /******************************************************************************************
2 *Filename: main.c
3 *Version: 1
4 *Author: Mostapha Abdelaziz
5 *Course: C Language
6 *Assignment Number: Assignment 2
7 *Assignment Name: Employee Database Implementation
8 *Purpose: Implement an employee database using linkedlist of structures
9 ******************************************************************************************/
10
11 #include "header.h"
12
13 /******************************************************************************************
14 *Function name: main
15 *Purpose: Main function for the employee database program calls other functions and loops through menu
16 *Function In parameters: None
17 *Function Out parameters: An integer for function success
18 *Version: 1
19 *Author: Mostapha Abdelaziz
20 ******************************************************************************************/
21 int main()
22 {
23 struct Employee *head;
24 struct Employee *employee;
25 int menuChoice = -1;
26 int empCount = 0;
27
28 /* print welcome */
29 printf("\nWelcome to the Employee Database\n--------------------------------\n");
30
31 /* allocate memory */
32 head = (struct Employee *)malloc(sizeof(struct Employee));
33 if (head == NULL)
34 {
35 printf("Error - could not allocate memory for an employee structure\n");
36 return EXIT_FAILURE;
37 }
38 head->next = NULL;
39
40 employee = (struct Employee *)malloc(sizeof(struct Employee));
41 if (employee == NULL)
42 {
43 printf("Error - could not allocate memory for an employee structure\n");
44 return EXIT_FAILURE;
45 }
46
47 /* loop through menu */
48 while (menuChoice != 5)
49 {
50 menuChoice = printMenu();
51 switch (menuChoice)
52 {
53 case 1:
54 /* add an employee if we do not have 150 */
55 if (empCount < 150)
56 {
57 employee->next = NULL;
58
59 /* ask for details */
60 printf("\nEnter information for employee %d\n\n", empCount + 1);
61 validateEmployeeDetails(employee);
62
63 /* first check if the name & age exist already */
64 if (empCount > 0 && findEmployee(head, employee->name, employee->age) == 0)
65 {
66 /* if they were found, print error */
67 printf("\nEmployee with name \"%s\" and age \"%d\" already exists. Employee was not added.\n", employee->name, employee->age);
68 }
69 else
70 {
71 /* otherwise place them in sorted */
72 addSortEmployee(head, employee, empCount);
73 empCount++;
74 }
75 }
76 else
77 {
78 printf("Database is full.\n");
79 }
80 break;
81 case 2:
82 /* delete an employee */
83 if (empCount > 0)
84 {
85 if (accessEmployee(head, employee, empCount, 1) == 1)
86 {
87 empCount--;
88 }
89 }
90 else
91 {
92 printf("There are no employees, use menu option 1 to add.\n");
93 }
94 break;
95 case 3:
96 /* edit an employee */
97 if (empCount > 0)
98 {
99 accessEmployee(head, employee, empCount, 2);
100 }
101 else
102 {
103 printf("There are no employees, use menu option 1 to add.\n");
104 }
105 break;
106 case 4:
107 /* print all employees */
108 if (empCount > 0)
109 {
110 printEmployees(head);
111 }
112 else
113 {
114 printf("There are no employees, use menu option 1 to add.\n");
115 }
116 break;
117 case 5:
118 /* exit program */
119 printf("\nGood Bye.\n");
120 break;
121 default:
122 return EXIT_FAILURE;
123 }
124 }
125
126 free(employee->next);
127 free(employee);
128 /* free every node */
129 while (head != NULL)
130 {
131 /* start from the head, free then move on */
132 employee = head;
133 head = head->next;
134 free(employee);
135 }
136
137 return EXIT_SUCCESS;
138 }
139
140 /******************************************************************************************
141 *Function name: menu
142 *Purpose: Prints the menu for the database functions and validates input
143 *Function In parameters: None
144 *Function Out parameters: The validated input for the menu
145 *Version: 1
146 *Authors: Mostapha Abdelaziz
147 ******************************************************************************************/
148 int printMenu()
149 {
150 char input[3];
151 int menuChoice = -1;
152
153 while (menuChoice == -1)
154 {
155 printf("\nPlease choose one of the following actions:\n1- Add an employee\n2- Delete an employee\n3- Edit an employee\n4- Print all employees\n5- Quit\nPlease your menu choice: ");
156
157 /* read input */
158 fgets(input, 5, stdin);
159 input[strcspn(input, "\n")] = 0;
160
161 /* check if it is an int, then range */
162 menuChoice = atoi(input);
163 if (menuChoice == 0)
164 {
165 if (menuChoice == 0 && input[0] == '0' && input[1] == '\0')
166 {
167 /* input was 0 */
168 printf("Option %d is not a valid choice. Options range from 1 to 5. Try again.\n", menuChoice);
169 menuChoice = -1;
170 }
171 else
172 {
173 /* input wasnt an int */
174 printf("Enter a valid whole number from 1 to 5. Try again.\n");
175 menuChoice = -1;
176 }
177 }
178 else if (menuChoice < 0 || menuChoice > 5)
179 {
180 /* if out of range */
181 printf("Option %d is not a valid choice. Options range from 1 to 5. Try again.\n", menuChoice);
182 menuChoice = -1;
183 }
184 }
185 return menuChoice;
186 }
187
188 /******************************************************************************************
189 *Function name: validateEmployeeDetails
190 *Purpose: Reads input and adds the information to a struct of an Employee
191 *Function In parameters: The employee to add information to
192 *Function Out parameters: None
193 *Version: 1
194 *Authors: Mostapha Abdelaziz
195 ******************************************************************************************/
196 void validateEmployeeDetails(struct Employee *employee)
197 {
198 char input[MAX_NAME_LENGTH];
199 int age = -1;
200 char tempChar;
201
202 input[0] = '\0';
203
204 /* ask for details and verify */
205 while (input[0] == '\0')
206 {
207 printf("Enter Employee Name: ");
208 /* store in temp variable, remove newline */
209 fgets(input, MAX_NAME_LENGTH, stdin);
210 input[strcspn(input, "\n")] = 0;
211 /* validate */
212 verifyString(input);
213 }
214 /* set first letter to capital if its a lower case letter */
215 tempChar = input[0];
216 if ((tempChar >= 97 && tempChar <= 122))
217 {
218 tempChar = tempChar - 32;
219 input[0] = tempChar;
220 }
221 /* copy into struct */
222 strcpy(employee->name, input);
223
224 input[0] = '\0';
225 /* ask for details and verify */
226 while (input[0] == '\0')
227 {
228 printf("Enter Employee Gender: ");
229 /* store and remove new line */
230 fgets(input, 20, stdin);
231 input[strcspn(input, "\n")] = 0;
232 /* validate */
233 verifyString(input);
234 }
235 /* set first letter to capital if its a lower case letter */
236 tempChar = input[0];
237 if ((tempChar >= 97 && tempChar <= 122))
238 {
239 tempChar = (tempChar - 32);
240 input[0] = tempChar;
241 }
242 /* copy into struct */
243 strcpy(employee->gender, input);
244
245 /* validate and save age */
246 while (age == -1)
247 {
248 printf("Enter Employee Age: ");
249 /* read input */
250 fgets(input, 20, stdin);
251 input[strcspn(input, "\n")] = 0;
252 age = validateInt(input);
253 }
254 employee->age = age;
255
256 input[0] = '\0';
257 /* ask for details and verify */
258 while (input[0] == '\0')
259 {
260 /* store and remove new line */
261 printf("Enter Employee Description: ");
262 fgets(input, MAX_JOB_LENGTH, stdin);
263 input[strcspn(input, "\n")] = 0;
264 /* validate */
265 verifyString(input);
266 }
267 /* set first letter to capital if its a lower case letter */
268 tempChar = input[0];
269 if ((tempChar >= 97 && tempChar <= 122))
270 {
271 tempChar = tempChar - 32;
272 input[0] = tempChar;
273 }
274 /* copy into struct */
275 strcpy(employee->description, input);
276 }
277
278 /******************************************************************************************
279 *Function name: validateInt
280 *Purpose: Reads input and validates an integer to ensure it is 0 or greater
281 *Function In parameters: The string input to validate if it was a integer
282 *Function Out parameters: The validated integer value
283 *Version: 1
284 *Authors: Mostapha Abdelaziz
285 ******************************************************************************************/
286 int validateInt(char *input)
287 {
288 int number;
289
290 /* check if it is an int, then range */
291 number = atoi(input);
292 if (number == 0)
293 {
294 if (number == 0 && input[0] == '0' && input[1] == '\0')
295 {
296 /* input was 0 */
297 printf("Cannot be 0. Try again.\n");
298 number = -1;
299 }
300 else
301 {
302 /* input wasnt an int */
303 printf("Input whole numbers only. try again.\n");
304 number = -1;
305 }
306 }
307 else if (number < 0)
308 {
309 /* if it is negative */
310 printf("Must be a positive number. Try again.\n");
311 number = -1;
312 }
313 else if (number > 150)
314 {
315 /* if it is too large */
316 printf("Input is too large. Try again.\n");
317 number = -1;
318 }
319
320 return number;
321 }
322
323 /******************************************************************************************
324 *Function name: verifyString
325 *Purpose: Takes a string and verifies it has no disallowed characters
326 *Function In parameters: The string to compare
327 *Function Out parameters: None
328 *Version: 1
329 *Authors: Mostapha Abdelaziz
330 ******************************************************************************************/
331 void verifyString(char *string)
332 {
333 char tempChar = string[0];
334 int i = 0;
335
336 /* confirm it does not begin with dash, apostrophe or space */
337 if (tempChar == 96 || tempChar == 45 || tempChar == 39 || tempChar == 32)
338 {
339 printf("Can not begin with \"%c\", try again.\n", tempChar);
340 i = strlen(string);
341 string[0] = '\0';
342 }
343 /* verify there are no invalid characters in the whole string */
344 while (i < strlen(string))
345 {
346 if (tempChar != 32 && tempChar != 39 && tempChar != 45 && tempChar != 96 && !(tempChar >= 65 && tempChar <= 90) && !(tempChar >= 97 && tempChar <= 122))
347 {
348 printf("Invalid character \"%c\" entered, try again.\n", tempChar);
349 string[0] = '\0';
350 i = strlen(string);
351 }
352 i++;
353 tempChar = string[i];
354 /* capitalise a letter if its preceeded by a space */
355 if (string[i - 1] == 32 && (tempChar >= 97 && tempChar <= 122))
356 {
357 tempChar = tempChar - 32;
358 string[i] = tempChar;
359 }
360 }
361 }
362
363 /******************************************************************************************
364 *Function name: addSortEmployee
365 *Purpose: Finds where to place the employee based on alphabetic order and places them
366 *Function In parameters: Head/first employee, employee being added and how many employees there are
367 *Function Out parameters: None
368 *Version: 1
369 *Authors: Mostapha Abdelaziz
370 ******************************************************************************************/
371 void addSortEmployee(struct Employee *head, struct Employee *employee, int empCount)
372 {
373
374 int i;
375
376 /* if it's the first one, add it to head otherwise make it current */
377 if (empCount == 0)
378 {
379 /* set as head */
380 *head = *employee;
381 }
382 else if (employee->name[0] < head->name[0])
383 {
384 /* if should be ordered before head, set head as the next data, and the employee as head */
385 if (employee->next == NULL)
386 {
387 employee->next = (struct Employee *)malloc(sizeof(struct Employee));
388 }
389 *employee->next = *head;
390 *head = *employee;
391 }
392 else
393 {
394 /* loop to check where it should enter */
395 for (i = 0; i < empCount; i++)
396 {
397 /* set head next if we are adding to the end */
398 if (head->next == NULL)
399 {
400 head->next = (struct Employee *)malloc(sizeof(struct Employee));
401 /* add to the end of list */
402 employee->next = NULL;
403 *head->next = *employee;
404 }
405 /* if its between two employees add in the middle */
406 else if (employee->name[0] < head->next->name[0])
407 {
408 /* add in sorted position */
409 if (employee->next == NULL)
410 {
411 employee->next = (struct Employee *)malloc(sizeof(struct Employee));
412 }
413 *employee->next = *head->next;
414 *head->next = *employee;
415
416 i = empCount;
417 }
418 head = head->next;
419 }
420 }
421 }
422
423 /******************************************************************************************
424 *Function name: findEmployee
425 *Purpose: Finds a provided employee based on name and age in provided list
426 *Function In parameters: The first employee in linked list, the employee name, the employee age
427 *Function Out parameters: Whether they were found or not
428 *Version: 1
429 *Authors: Mostapha Abdelaziz
430 ******************************************************************************************/
431 int findEmployee(struct Employee *head, char *name, int age)
432 {
433 int i = 1;
434
435 /* first check if it is the head */
436 if (strcmp(name, head->name) == 0 && head->age == age)
437 {
438 /* if it is return true for found */
439 return 0;
440 }
441 else
442 {
443 /* otherwise loop through until they're found */
444 while (head->next != NULL)
445 {
446 /* if its a match return success */
447 if (strcmp(name, head->next->name) == 0 && head->next->age == age)
448 {
449 return 0;
450 }
451 i++;
452 head = head->next;
453 }
454 }
455
456 /* if they were not found return false */
457 return 1;
458 }
459
460 /******************************************************************************************
461 *Function name: printEmployees
462 *Purpose: Prints all employees and their information
463 *Function In parameters: The first employee in linked list to print
464 *Function Out parameters: None
465 *Version: 1
466 *Authors: Mostapha Abdelaziz
467 ******************************************************************************************/
468 void printEmployees(struct Employee *employee)
469 {
470 int count = 1;
471
472 printf("\n-------------------------\n--- Employee Database ---\n-------------------------\n\n");
473 /* loop through until the struct is null */
474 while (employee != NULL)
475 {
476 /* print information */
477 printf("Employee %d\n------------\nName: %s \nGender: %s \nAge: %d \nJob Description: %s\n\n", count, employee->name, employee->gender, employee->age, employee->description);
478 /* increment count, set struct to next one */
479 count++;
480 employee = employee->next;
481 }
482 }
483
484 /******************************************************************************************
485 *Function name: accessEmployee
486 *Purpose: Accesses an selected employee to edit or delete them
487 *Function In parameters: The head of the linked list, a temporary employee, the number of employees and option for deleting or editing
488 *Function Out parameters: Integer how many were deleted
489 *Version: 1
490 *Authors: Mostapha Abdelaziz
491 ******************************************************************************************/
492 int accessEmployee(struct Employee *head, struct Employee *employee, int empCount, int option)
493 {
494 int success;
495 int i = 1;
496 char input[5];
497 int number = -1;
498 char *message;
499 int found = 0;
500 char name[MAX_NAME_LENGTH];
501 int age;
502 struct Employee *temp;
503
504 /* set a variable for deleting or editing */
505 if (option == 1)
506 {
507 message = "Delete";
508 }
509 else
510 {
511 message = "Edit";
512 }
513
514 printEmployees(head);
515
516 /* ask which one to delete */
517 while (number == -1)
518 {
519 printf("Enter employee number to select: ");
520 /* read input */
521 fgets(input, 20, stdin);
522 input[strcspn(input, "\n")] = 0;
523 number = validateInt(input);
524
525 if (number > empCount)
526 {
527 printf("Employee %d is the last employee, %d is too large. Try again.\n", empCount, number);
528 number = -1;
529 }
530 }
531
532 /* Loop until employee */
533 if (number > 2)
534 {
535 for (i = 1; i < number - 1; i++)
536 {
537 head = head->next;
538 }
539 }
540
541 /* confirm */
542 input[0] = '\0';
543 while (input[0] == '\0')
544 {
545 if (number == 1)
546 {
547 printf("%s employee %d: %s, age: %d ? (\"y\" for yes, \"n\" for no): ", message, number, head->name, head->age);
548 }
549 else
550 {
551 printf("%s employee %d: %s, age: %d ? (\"y\" for yes, \"n\" for no): ", message, number, head->next->name, head->next->age);
552 }
553 fgets(input, 20, stdin);
554 input[strcspn(input, "\n")] = 0;
555 /* lower case the letter */
556 if (input[0] >= 65 && input[0] <= 90)
557 {
558 input[0] = input[0] + 32;
559 }
560 /* check if valid */
561 if (input[1] != '\0' || (input[0] != 'y' && input[0] != 'n'))
562 {
563 printf("Invalid input \"%s\", try again.\n", input);
564 input[0] = '\0';
565 }
566 }
567
568 /* if they cancel set success as 0, else success is employee position */
569 if (input[0] != 'n')
570 {
571 success = number;
572 }
573 else
574 {
575 success = 0;
576 }
577
578 /* if employee found, delete and edit - function prints by default */
579 if (success != 0)
580 {
581 /* if we are deleting or editing the head */
582 if (success == 1)
583 {
584 /* copy if editing and delete the head */
585 if (option == 2)
586 {
587 *employee = *head;
588 employee->next = NULL;
589 }
590 if (head->next != NULL)
591 {
592 temp = head->next;
593 *head = *head->next;
594 free(temp);
595 }
596 else
597 {
598 head = NULL;
599 }
600 /* if we are deleting, print so otherwise enter new employee details */
601 if (option == 1)
602 {
603 printf("Employee was deleted.\n");
604 return 1;
605 }
606 else
607 {
608 /* edit the copied employee then re sort */
609 /* copy original name and age in case of duplicate */
610 strcpy(name, employee->name);
611 age = employee->age;
612
613 /* edit the employee */
614 editEmployee(employee);
615
616 /* first check if the name & age exist already */
617 found = findEmployee(head, employee->name, employee->age);
618 if (found == 0)
619 {
620 /* if they were found, print error */
621 printf("\nEmployee with name \"%s\" and age \"%d\" already exists. Changes were not made.\n", employee->name, employee->age);
622
623 /* copy original values back */
624 employee->age = age;
625 strcpy(employee->name, name);
626 }
627
628 /* insert employee */
629 addSortEmployee(head, employee, empCount - 1);
630 }
631 }
632 /* if we are editing or deleting other than the head */
633 else
634 {
635 /* copy if editing then remove the one after head */
636 if (option == 2)
637 {
638 *employee = *head->next;
639 employee->next = NULL;
640 }
641 temp = head->next;
642 head->next = head->next->next;
643 free(temp);
644 /* if we are deleting, print so otherwise enter new employee details */
645 if (option == 1)
646 {
647 printf("Employee was deleted.\n");
648 return 1;
649 }
650 else
651 {
652 /* edit the copied employee then re sort */
653 /* copy original name and age in case of duplicate */
654 strcpy(name, employee->name);
655 age = employee->age;
656
657 /* edit the employee */
658 editEmployee(employee);
659
660 /* first check if the name & age exist already */
661 found = findEmployee(head, employee->name, employee->age);
662 if (found == 0)
663 {
664 /* if they were found, print error */
665 printf("\nEmployee with name \"%s\" and age \"%d\" already exists. Changes were not made.\n", employee->name, employee->age);
666
667 /* copy original values back */
668 employee->age = age;
669 strcpy(employee->name, name);
670 }
671
672 /* insert employee */
673 addSortEmployee(head, employee, empCount - 1);
674 }
675 }
676 }
677 return 0;
678 }
679
680 /******************************************************************************************
681 *Function name: editEmployee
682 *Purpose: Asks what to edit of a provided employee
683 *Function In parameters: The employee to edit
684 *Function Out parameters: None
685 *Version: 1
686 *Authors: Mostapha Abdelaziz
687 ******************************************************************************************/
688 void editEmployee(struct Employee *employee)
689 {
690 char menuOption[10];
691 char string[MAX_NAME_LENGTH];
692 int age = -1;
693 int success;
694
695 /* loop for validation */
696 success = 1;
697 while (success == 1)
698 {
699 /* ask for what to change */
700 printf("Enter the corresponding option\n 1. Name\n 2. Gender\n 3. Age\n 4. Description\n > ");
701 fgets(menuOption, 10, stdin);
702 menuOption[strcspn(menuOption, "\n")] = 0;
703
704 /* if invalid print so */
705 if (menuOption[1] != '\0' || (menuOption[0] != '1' && menuOption[0] != '2' && menuOption[0] != '3' && menuOption[0] != '4'))
706 {
707 printf("Invalid menu choice \"%s\", try again.\n", menuOption);
708 success = 1;
709 }
710 else
711 {
712 /* otherwise implement choice */
713 success = 0;
714 string[0] = '\0';
715 switch (menuOption[0])
716 {
717 case '1':
718 /* ask for name */
719 while (string[0] == '\0')
720 {
721 printf("Enter new Employee Name: ");
722 /* store in temp variable, remove newline */
723 fgets(string, MAX_NAME_LENGTH, stdin);
724 string[strcspn(string, "\n")] = 0;
725 /* validate */
726 verifyString(string);
727 }
728 /* set first letter to capital if its a lower case letter */
729 if ((string[0] >= 97 && string[0] <= 122))
730 {
731 string[0] = string[0] - 32;
732 }
733
734 /* change employee name */
735 strcpy(employee->name, string);
736 break;
737 case '2':
738 /* ask for gender */
739 while (string[0] == '\0')
740 {
741 printf("Enter new Employee gender: ");
742 /* store in temp variable, remove newline */
743 fgets(string, MAX_NAME_LENGTH, stdin);
744 string[strcspn(string, "\n")] = 0;
745 /* validate */
746 verifyString(string);
747 }
748 /* set first letter to capital if its a lower case letter */
749 if ((string[0] >= 97 && string[0] <= 122))
750 {
751 string[0] = string[0] - 32;
752 }
753
754 /* change employee gender */
755 strcpy(employee->gender, string);
756 break;
757 case '3':
758 /* ask for employee age */
759 while (age == -1)
760 {
761 printf("Enter Employee Age: ");
762 /* read input */
763 fgets(string, 5, stdin);
764 string[strcspn(string, "\n")] = 0;
765 age = validateInt(string);
766 }
767 /* change employee age */
768 employee->age = age;
769 break;
770 case '4':
771 /* ask for description */
772 while (string[0] == '\0')
773 {
774 printf("Enter new Employee description: ");
775 /* store in temp variable, remove newline */
776 fgets(string, MAX_NAME_LENGTH, stdin);
777 string[strcspn(string, "\n")] = 0;
778 /* validate */
779 verifyString(string);
780 }
781 /* set first letter to capital if its a lower case letter */
782 if ((string[0] >= 97 && string[0] <= 122))
783 {
784 string[0] = string[0] - 32;
785 }
786
787 /* change employee description */
788 strcpy(employee->description, string);
789 break;
790 default:
791 printf("No changes were made.\n");
792 break;
793 }
794 }
795 }
796 }
797