Adding the printf("Hi!\n") statements allows the code to work. It also works if the bound initial bound is improper and the user enters a new one. When I ran some tests calculate divers sometimes returned a character instead of an integer. I'm thinking it has something to do with my memory allocation. I also noticed that ./a.out 6 10 "|" would work but ./a.out 6 25 "|" would not causing an infinite loop when printing the lines of "|".
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
// Structs
typedef struct data_struct {
int lineNumber;
int divisorSum;
char type[10];
}data;
// Prototypes
int calculateDivsors(int integer);
// Functions
int main (int argc, char *argv[]) {
int lowerBound;
int upperBound;
char character;
// Gets the values from command-line
sscanf(argv[1], "%d", &lowerBound);
sscanf(argv[2], "%d", &upperBound);
sscanf(argv[3], "%c", &character);
// Check to see if bound is proper
while (upperBound <= lowerBound || lowerBound < 2) {
printf("Error, please enter a new range (positive increasing).\n");
scanf("%d %d", &lowerBound, &upperBound);
}
// Structure calls
data* info = NULL;
int totalData = upperBound - lowerBound;
// Allocate the memory
info = (data*)malloc(totalData * sizeof(data));
printf("Hi!\n");
if (info != NULL) {
// Iterate through all the digits between the two bounds
for (int i = lowerBound; i <= upperBound; i++) {
int sum = calculateDivsors(i);
// Write data to indiviual structures
info[i].lineNumber = i;
info[i].divisorSum = sum;
// Check to see if the sum is greater than, less than, or equal to the original
if (sum == i) {
strcpy(info[i].type, "Perfect");
}
else if (sum > i) {
strcpy(info[i].type, "Abundant");
}
else if (sum < i) {
strcpy(info[i].type, "Deficient");
}
// Line n# has a column width of 4, string of 10
printf("%4d is %-10s\t", info[i].lineNumber, info[i].type);
// Generate Pictogram
for (int j = 0; j < info[i].divisorSum; j++) {
printf("%c", character);
}
printf("\n");
}
}
}
// Adds up the sum of diviors
int calculateDivsors(int integer) {
int sum = 0;
for (int i = 1; i < integer; i++) {
// Add to sum if perfectly i is a sum of integer
if (integer % i == 0) {
sum += i;
}
}
return sum; // Returns the sum of diviors
}

printfnor without it.iused forinfo[i]indexing of your allocation is not zero based, but the allocation size,totalData, is (correctly, btw). Therefore, asiincreases it will breachtotalSizeand in so doing, you're program invokes undefined behavior. Also totalData should be sized asint totalData = upperBound - lowerBound + 1;