How do you properly allocate space in C - c

Question

I'm writing a program in C and I'm aware you have to allocate appropriate space for efficient code but am unsure of how to start, I've written and completed my program and it would be a shame to restart. If anyone can guide me how to properly malloc space for my program it would be appreciated.
Here is my code as follows:
main.c
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include "courses.h"
int main (int argc, char *argv[]) {
srand (time(NULL));
createStudents ();
createCourses ();
regiserStudents ();
printCourses ();
return 1;
}
courses.c
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include "structs.h"
void createStudents () {
int random, i;
for (i = 0; i < 12; i++) {
students[i].firstName = *firstName[i];
students[i].lastName = *lastName[i];
random = 10000 + rand() % 89999;
students[i].num.studentNum = random;
printf("%d - %s, %s \n", students[i].num.studentNum, students[i].lastName, students[i].firstName);
}
}
void createCourses () {
int numbers[999];
int numbersLeft = 999;
char courseCode[512];
int numCourses = 3;
int random, i, j;
for (i = 0; i < 999; i++) {
numbers[i] = i;
}
for (j = 0; j < numCourses; j++) {
random = rand() % numbersLeft;
if (random < 10) {
snprintf(courseCode, sizeof courseCode, "CS00%d", random);
}
else if (random < 100 && random > 9) {
snprintf(courseCode, sizeof courseCode, "CS0%d", random);
}
else {
snprintf(courseCode, sizeof courseCode, "CS%d", random);
}
courses[j].cName = courseName[j];
courses[j].cDescription = courseDescription[j];
courses[j].cCode = courseCode;
numbers[random] = numbers[numbersLeft-1];
numbersLeft--;
random = 4 + rand() % 4;
courses[j].maxRegister = random;
}
}
void regiserStudents () {
int checkSum = 0, checkSum1 = 0, checkTemp = 0, count0 = 0, count1 = 0, count2 = 0;
int v, i, j, random;
for (i = 0; i < 2; i++) {
checkTemp = count0;
for (j = 0; j < 12; j++) {
random = rand() % 3;
if (random == 0) {
if (count0 == 0) {
courses[random].registered[count0] = &students[j];
count0++;
}
else {
checkSum1 = students[j].num.studentNum;
for (v = 0; v < checkTemp; v++) {
checkSum = courses[0].registered[v]->num.studentNum;
if (checkSum == checkSum1) {
/*Do Nothing*/
}
else {
courses[random].registered[count0] = &students[j];
count0++;
}
}
}
}
if (random == 1) {
if (count1 == 0) {
courses[random].registered[count1] = &students[j];
count1++;
}
else {
checkSum1 = students[j].num.studentNum;
for (v = 0; v < checkTemp; v++) {
checkSum = courses[1].registered[v]->num.studentNum;
if (checkSum == checkSum1) {
/*Do Nothing*/
}
else {
courses[random].registered[count1] = &students[j];
count1++;
}
}
}
}
if (random == 2) {
if (count2 == 0) {
courses[random].registered[count2] = &students[j];
count2++;
}
else {
checkSum1 = students[j].num.studentNum;
for (v = 0; v < checkTemp; v++) {
checkSum = courses[2].registered[v]->num.studentNum;
if (checkSum == checkSum1) {
/*Do Nothing*/
}
else {
courses[random].registered[count2] = &students[j];
count2++;
}
}
}
}
}
}
courses[0].studentRegistered = count0;
courses[1].studentRegistered = count1;
courses[2].studentRegistered = count2;
}
void printCourses () {
int i;
printf("\n%s - %s\n%s\nRegistered Students (%d/%d):\n", courses[0].cCode, courses[0].cName, courses[0].cDescription, courses[0].studentRegistered, courses[0].maxRegister);
for (i = 0; i < courses[0].studentRegistered; i++) {
printf("%d - %s, %s \n", courses[0].registered[i]->num.studentNum, courses[0].registered[i]->lastName, courses[0].registered[i]->firstName);
}
printf("\n%s - %s\n%s\nRegistered Students (%d/%d):\n", courses[1].cCode, courses[1].cName, courses[1].cDescription, courses[1].studentRegistered, courses[1].maxRegister);
for (i = 0; i < courses[1].studentRegistered; i++) {
printf("%d - %s, %s \n", courses[1].registered[i]->num.studentNum, courses[1].registered[i]->lastName, courses[1].registered[i]->firstName);
}
printf("\n%s - %s\n%s\nRegistered Students (%d/%d):\n", courses[2].cCode, courses[2].cName, courses[2].cDescription, courses[2].studentRegistered, courses[2].maxRegister);
for (i = 0; i < courses[2].studentRegistered; i++) {
printf("%d - %s, %s \n", courses[2].registered[i]->num.studentNum, courses[2].registered[i]->lastName, courses[2].registered[i]->firstName);
}
}
courses.h
#ifndef COURSES_H_
#define COURSES_H_
void createStudents();
void createCourses ();
void regiserStudents ();
void printCourses ();
#endif
structs.h
#ifndef STRUCTS_H_
#define STRUCTS_H_
char *firstName[] = {
"Emma", "Liam", "Olivia",
"Noah", "Ava", "Logan",
"Sophia", "Lucas", "Isabella",
"Mason", "Shaylyn", "Jack"
};
char *lastName[] = {
"Smith", "Johnson", "Williams",
"Brown", "Jones", "Miller",
"Davis", "Garcia", "Rodriguez",
"Wilson", "Seguin", "Loveday"
};
typedef struct{
int studentNum;
}studentNumber;
typedef struct{
char *firstName;
char *lastName;
studentNumber num;
}studentID;
studentID students[12];
char *courseName[] = {"Web Programming", "Technical Communication", "Processor Architecture"};
char *courseDescription[] = {"Learn to make websites!", "Learn the essentials of communication skills", "Learn the basics of circuits and Machine Language coding"};
typedef struct {
int maxRegister;
char *cCode;
char *cName;
char *cDescription;
studentID *registered[8];
studentID *waitlisted[12];
int studentRegistered;
int studentWaitlisted;
}course;
course courses[3];
#endif
Essentially the program should run as: create students, create random school courses, fill the students into the courses, and then print everything while accessing the structs from a header file (structs.h)
Here's the message I receive of running the program after it compiles:
Segmentation fault (core dumped)

Answer 1

In createStudents(), you don't need to dereference firstName[i] nor lastName[i]:
students[i].firstName = *firstName[i];
students[i].lastName = *lastName[i];
Since firstName[i] already gives you a char *, you can assign that pointer directly to students[i].firstName (same goes for lastName):
students[i].firstName = firstName[i];
students[i].lastName = lastName[i];