User assigned values into an Array

[Mark Labarbara]

Hey guys! I have been using this site for a while now I gotta say, I love it!

I have a question now, though. I am writing a very simple program where a user can input 10 GPA's and then list them in either ascending or descending order. I am running into an issue though. I have tried two different ways so far, but neither seem to be working.

This first way gets the loop that I want, but when the last 'printf' is called, it always displays random numbers...

main()
 {
    float iGpa[10];
    int x=0;

    while (x<10){
        printf("Please enter 10 GPA's\n: ", x++);
        scanf("%f", &iGpa[x]);
    }
    printf("%f", iGpa[10]);
}

...And for this one, I get a SEGFAULT error

main()
{

    float iGpa[10];
    int x=0;

    for(x=0;x<10;x++){
        printf("Enter 10 GPA's: ",x++);
        scanf("%f", &iGpa[10]);
    }
    prinf("%f", iGpa[10]);
}

My suspicion is either my code to assign the values into the array is incorrect, of my code to display the array is incorrect, but I can not figure out a which/how.

Also, I am pretty sure I could get it if I assign each GPA to it's own variable, but I would rather a loop for cleaner code.

Any help is greatly appreciated, Thanks!

[Tclausex]

In the first, you are incrementing x before you scanf, increment in scanf and that problem is solved.

In both you are referring to an out of bounds index. Remember array indexes start with zero and end with N-1.

To print each element of the array, use a for loop.

[Mark Labarbara]

In the first, you are incrementing x before you scanf, increment in scanf and that problem is solved.

In both you are referring to an out of bounds index. Remember array indexes start with zero and end with N-1.

I know that the indexes will be 0-9 (which=10), but how would I tell it to assign the values in iGpa[0], iGpa[1], etc... in the loop? Do I need to remove the [10] from the scanf?

[failure67]

In a for loop:

int i;
int myArray[10];

/*Placing stuff into an array*/
for(i = 0; i < 10; i++)
{
     myArray[i] = /* some value */
}

/* Some intermediate steps... */

/*Printing values from an array*/
for(i = 0; i < 10; i++)
{
     printf("myArray[%d] = %d", i, myArray[i]);
}

[Tclausex]

Your first code was correct up to the printf and needing to increment x in scanf.

Yes. iGpa[10] refers to nothing - it is out of bounds of the array. And using an incrementing variable is how to step through an array.

[Mark Labarbara]

In a for loop:

int i;
int myArray[10];

/*Placing stuff into an array*/
for(i = 0; i < 10; i++)
{
     myArray[i] = /* some value */
}

/* Some intermediate steps... */

/*Printing values from an array*/
for(i = 0; i < 10; i++)
{
     printf("myArray[%d] = %d", i, myArray[i]);
}

Thanks for the help, but I already know that. The problem I am having is getting the array values to be assigned by the user input.

Your first code was correct up to the printf and needing to increment x in scanf.

Yes. iGpa[10] refers to nothing - it is out of bounds of the array. And using an incrementing variable is how to step through an array.

After changing the x++ to scanf, it still doesn't work right. When the last printf is called, it just displays the last gpa entered (i.e. if the last gpa was 3 it will display 3.00000).

I am sorry, but I am just not understanding what you are saying, I suppose.

[Tclausex]

main()
 {
    float iGpa[10];
    int x=0;

    while (x<10){
        printf("Please enter 10 GPA's\n: ");
        scanf("%f", &iGpa[x++]);
    }
    
}

This is correct! Just moved where the increment occurred.

[Mark Labarbara]

main()
 {
    float iGpa[10];
    int x=0;

    while (x<10){
        printf("Please enter 10 GPA's\n: ");
        scanf("%f", &iGpa[x++]);
    }
    
}

This is correct! Just moved where the increment occurred.

If I do it that way, how would I print the contents of the array?

[Tclausex]

If I do it that way, how would I print the contents of the array?

That was already answered.

[Mark Labarbara]

That was already answered.

When I do it that way

main()
{
    float iGpa[10];
    int x;


    while (x<10){
        printf("Enter 10 GPA's\n: ");
        scanf("%f", &iGpa[x++]);
    }
    for (x=0;x<10;x++){
        printf("\niGpa[%d] = %f", x, iGpa[x]);
    }
}

the output is

 
$ ./GPA
iGpa[0]= 0
iGpa[1]= 536870912
iGpa[2]= 536870912
iGpa[3]= 0
etc...
...

It never lets me input the ten GPA's and prints random numbers.

[Tclausex]

What is your input?

Of course the output is bad. Look at your printf format specifiers and ask yourself if they match the variables' data types.

[failure67]

Hint: What is %d and %f used for?

[Mark Labarbara]

What is your input?

Of course the output is bad. Look at your printf format specifiers and ask yourself if they match the variables' data types.

Sorry about that, typed it wrong. Still doesn't work though...

Hint: What is %d and %f used for?

integer and float. But when I fixed that, the program still won't let me input numbers and outputs different random numbers.

[Tclausex]

Your problem is yet another format specifier - look at your scanf.

[Mark Labarbara]

Fixed, still not it.

Does the same thing, doesn't let me input any numbers and goes straight to the for loop and prints random numbers.

Thanks again for all of your help, guys. I really appreciate it