Why does my program keep printing garbage values? - c

Question

For some reason when i input my time , description and index and click quit to print the array that i have populated with values and strings, i get a bunch of garbage values printed instead of what i inputed, not sure what im doing wrong. any advice?
For some reason when i input my time , description and index and click quit to print the array that i have populated with values and strings, i get a bunch of garbage values printed instead of what i inputed, not sure what im doing wrong. any advice?
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX 5
struct event //data type called event which holds time and description for events
{
int hour; //holds the hour digit between 0-23
int minute; //holds the minute digit between 0-59
char description[41];
//holds the description for the reason of the alarm
};
typedef struct event Event; //allows coder to only have to use "Event" instead of "struct event"
int InputRange(int min, int max);
Event* InputEvent(Event *newEvent);
int AddEventAtIndex(Event list[], Event e, int i);
//int InsertionSortEvent(Event list[], int *p_size, Event e);
//void DisplayEvent(Event e);
//void DisplayEventList(Event list[], int size);
//int DeleteEvent(Event list[], int i, int *p_size);
int main (void)
{
Event EventList[MAX];
Event e;
int i=0;
int eventListSize = 0;
int choice;
do
{
printf("__= Scheduler v1.0 =__\n");
printf("1. Schedule an event.\n");
printf("2. Delete an event.\n");
printf("3. Display schedule.\n");
printf("4. Save schedule.\n");
printf("5. Load schedule.\n");
printf("6. Exit\n");
switch(choice = InputRange(1, 6))
{
case 1: InputEvent( EventList );
i = AddEventAtIndex(EventList, e, i);
break;
/* case 2: pHead = deleteStudent(pHead);
break;
case 3: printf("Press 1 to search by ID or 2 to search by name: \n");
scanf("%d", &search);
if (search == 1){
searchStudentID(pHead);
}
else if (search == 2){
searchStudentlName(pHead);
}
else{
printf("Invalid selection");
}
break;
case 4: displayStudentInfo(pHead);
break;
case 5: saveStudentInfo(pHead);
break;
case 6: end(pHead);
break;*/
default: printf("Exiting Program\n\n");
}
}
while ( choice != 6 );
printf("Index #[]\tTime\tDescription");
for ( int j = 1; j < 6; j++)
{
printf("\n[%d]\n\t%d:%d \t %s", j, EventList[j].hour,
EventList[j].minute, EventList[j].description);
}
}
int InputRange(int min, int max)
{
int timenumber;
printf("Please enter a number between %d - %d\n", min, max);
scanf("%d", &timenumber);
printf("\n");
if (timenumber < min || timenumber > max)
{
printf("Invalid Entry\n");
InputRange(min, max);
}
return timenumber;
}
Event* InputEvent(Event *newEvent)
{
if (newEvent != NULL) // quality assurance:
// make sure the pointer is valid
{
printf("Enter the event time:\n");
newEvent->hour = InputRange(0, 23);
newEvent->minute = InputRange(0, 59);
printf("Enter the event description:\n");
fgetc(stdin);
fgets(newEvent->description, 41, stdin);
printf("\n");
}
return newEvent;
}
int AddEventAtIndex(Event list[], Event e, int i)
{
--i;
printf("Where in the array would you like to store this event\n");
i = InputRange(1, 5);
list[i].hour = e.hour;
list[i].minute = e.minute;
strcpy(list[i].description, e.description);
return i;
}

Answer 1

Why does my program keep printing garbage values?
You use non initialized data, in main you have :
Event e;
...
i = AddEventAtIndex(EventList, e, i);
where e is not initialized but used in AddEventAtIndex :
int AddEventAtIndex(Event list[], Event e, int i)
{
...
list[i].hour = e.hour;
list[i].minute = e.minute;
strcpy(list[i].description, e.description);
the behavior of strcpy with an non initialized value is undefined and can have a dramatic consequences.
Probably the call InputEvent( EventList ); must be replaced by InputEvent(&e);
In
for ( int j = 1 ; j < 6 ; j++)
{
printf("\n[%d]\n\t%d:%d \t %s", j, EventList[j].hour,
EventList[j].minute, EventList[j].description);
}
You access out of EventList when j is 5 and 6, do for instance :
for ( int j = 0 ; j < MAX ; j++)
{
printf("[%d]\t%d:%d \t %s\n", j+1, EventList[j].hour,
EventList[j].minute, EventList[j].description);
}
But you also write entries never set printing 'garbage values', more the fact to print a string non initialized has undefined effect. A way to separate entries set and not set is to initialize all the hours by 24 and to test that value in the loop to write or not the entry.
I also changed the format because the newline after the index is not compatible with printf("Index #[]\tTime\tDescription"); and it is better to put the other newline after all rather than before to flush the output line, so also change printf("Index #[]\tTime\tDescription"); by puts("Index #[]\tTime\tDescription");
MAX is not a very good name because it is more a SUP, or just rename it by SIZE
In main you do not use eventListSize
In AddEventAtIndex
--i must be done after i = InputRange(1, 5); or just do i = InputRange(1, 5) - 1; else when i values 5 list[i] is out of list so you write out of list with an undefined behavior.
So finally the parameter i is useless, remove it.
The return index is also not used in main, you use it to assign i and do not used the value of i after. AddEventAtIndex do not need to return a value.
In InputRange
You do not check the result of scanf so the value of timenumber is undefined if a non valid integer was enter and if you do not purge the input so all the next scanf to get a number will not success
Also if the value is not in the range you just call InputRange(min, max); without returning its value so you finally return the invalid value, put all in a for(;;) for instance to only return when the value is correct.
You use fgets in InputEvent, to mix it with scanf to read number is a source of problem, replace the scanf by the use of fgets then a sscanf on the read line
In InputEvent
When you do fgetc(stdin); you probably hope to bypass a newline but if the user enter characters after the number in InputRange (supposing a number was enter) fgets will read the first of them and fgets will not get the expected description. The solution is to do fgets then sscanf in InputRange as I said above allowing you to remove that fgetc
A proposal taking into account my remarks :
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX 5
struct event //data type called event which holds time and description for events
{
int hour; //holds the hour digit between 0-23
int minute; //holds the minute digit between 0-59
char description[41]; //holds the description for the reason of the alarm
};
typedef struct event Event; //allows coder to only have to use "Event" instead of "struct event"
int InputRange(int min, int max);
Event* InputEvent(Event *newEvent);
void AddEventAtIndex(Event list[], Event e);
//int InsertionSortEvent(Event list[], int *p_size, Event e);
//void DisplayEvent(Event e);
//void DisplayEventList(Event list[], int size);
//int DeleteEvent(Event list[], int i, int *p_size);
int main (void)
{
Event EventList[MAX];
Event e;
int choice;
/* mark uset entries */
for (int i = 0; i != MAX; ++i)
EventList[i].hour = 24;
do
{
printf("__= Scheduler v1.0 =__\n");
printf("1. Schedule an event.\n");
printf("2. Delete an event.\n");
printf("3. Display schedule.\n");
printf("4. Save schedule.\n");
printf("5. Load schedule.\n");
printf("6. Exit\n");
switch(choice = InputRange(1, 6))
{
case 1:
InputEvent( &e );
AddEventAtIndex(EventList, e);
break;
/*case 2: pHead = deleteStudent(pHead);
break;
case 3: printf("Press 1 to search by ID or 2 to search by name: \n");
scanf("%d", &search);
if (search == 1){
searchStudentID(pHead);
}
else if (search == 2){
searchStudentlName(pHead);
}
else{
printf("Invalid selection");
}
break;
case 4: displayStudentInfo(pHead);
break;
case 5: saveStudentInfo(pHead);
break;
case 6: end(pHead);
break;*/
default: printf("Exiting Program\n\n");
}
}
while ( choice != 6 );
puts("Index #[]\tTime\tDescription");
for ( int j = 0 ; j < MAX ; j++)
{
if (EventList[j].hour != 24)
printf("\t[%d]\t%d:%d \t %s\n", j+1, EventList[j].hour,
EventList[j].minute, EventList[j].description);
}
}
int InputRange(int min, int max)
{
char line[32];
int timenumber;
for (;;) {
printf("Please enter a number between %d - %d\n", min, max);
if (fgets(line, sizeof(line), stdin) == NULL)
/* EOF */
exit(-1);
if ((sscanf(line, "%d", &timenumber) == 1) &&
(timenumber >= min) &&
(timenumber <= max))
return timenumber;
printf("Invalid Entry\n");
}
}
Event* InputEvent(Event *newEvent)
{
if (newEvent != NULL) // quality assurance:
// make sure the pointer is valid
{
printf("Enter the event time:\n");
newEvent->hour = InputRange(0, 23);
newEvent->minute = InputRange(0, 59);
printf("Enter the event description:\n");
fgets(newEvent->description, sizeof(newEvent->description), stdin);
printf("\n");
}
return newEvent;
}
void AddEventAtIndex(Event list[], Event e)
{
printf("Where in the array would you like to store this event\n");
int i = InputRange(1, 5) - 1;
list[i].hour = e.hour;
list[i].minute = e.minute;
strcpy(list[i].description, e.description);
}
Compilation and execution :
pi#raspberrypi:/tmp $ gcc -g -pedantic -Wextra -Wall c.c
pi#raspberrypi:/tmp $ ./a.out
__= Scheduler v1.0 =__
1. Schedule an event.
2. Delete an event.
3. Display schedule.
4. Save schedule.
5. Load schedule.
6. Exit
Please enter a number between 1 - 6
1
Enter the event time:
Please enter a number between 0 - 23
2
Please enter a number between 0 - 59
22
Enter the event description:
descr1
Where in the array would you like to store this event
Please enter a number between 1 - 5
1
__= Scheduler v1.0 =__
1. Schedule an event.
2. Delete an event.
3. Display schedule.
4. Save schedule.
5. Load schedule.
6. Exit
Please enter a number between 1 - 6
1
Enter the event time:
Please enter a number between 0 - 23
3
Please enter a number between 0 - 59
33
Enter the event description:
descr2
Where in the array would you like to store this event
Please enter a number between 1 - 5
4
__= Scheduler v1.0 =__
1. Schedule an event.
2. Delete an event.
3. Display schedule.
4. Save schedule.
5. Load schedule.
6. Exit
Please enter a number between 1 - 6
12
Invalid Entry
Please enter a number between 1 - 6
6
Exiting Program
Index #[] Time Description
[1] 2:22 descr1
[4] 3:33 descr2
note the empty line in the final print, this is because the newline is part of the description, it must be remove is present in InputEvent