Why array variable doesn't work inside the IF statement of C?

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I wrote a C program using VS code, and tried to assign a string to an array inside an If-statement of C language. But it doesn't work. However, only integer variables are successfully assigned. Why is that?

Here is the code:

C

#include <stdio.h>

int main ()
{
    char NumberType[] = "POSITIVE";
    int Number;
    printf("Enter a number: ");
    scanf ("%d", &Number);
    if (Number <0)
    {
        NumberType[10] = "NEGATIVE";
    }

    if (Number == 0)
    {
        Number = 4;
    }

    Number = (Number/2);
    printf("The number divided by 2 is %d and it's a %s number", Number, NumberType);
    return 0;
}

What I have tried:

The string "NEGATIVE" can't be assigned to the array NumberType[10] when the first if-statement is entered, but the integer '4' is assigned to 'Number' variable when the second if-statement is entered.

Posted 24-May-23 1:39am

Member 8730814

Updated 24-May-23 2:20am

Richard Deeming

v2

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2 solutions

Solution 1

Quote:

C

NumberType[10] = "NEGATIVE";

That attempts to store an array of chars in element 10 of an eight-element array of char values. That's not going to work.

c - Assigning strings to arrays of characters - Stack Overflow[^]

Apparently, you can't assign one array to another in C, so NumberType = "NEGATIVE"; won't work. You'll need to use strcpy instead.

C

strcpy(NumberType, "NEGATIVE");

Posted 24-May-23 2:02am

Richard Deeming

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OriginalGriff · Accepted Answer · 2023-05-24T02:20:00

To add to what Richard has said, this code can never work:

    char NumberType[] = "POSITIVE";
...
        NumberType[10] = "NEGATIVE";

because NumberType is an array of characters, and so is "NEGATIVE" (string literals are stored as an array of characters because C has no concept of strings). You are trying to assign nine characters (because C strings are null terminated which means they have a "hidden character" at the end which tells the system when to stop processing it) into a single character location in a character array which will not fit.

In fact it's worse than that, because the assignment would attempt to write a pointer value (because arrays are really pointers to the data they contain) and that means it would get really messed up depending on the size of a pointer in your system.

What I'd suggest is to use a flag which says if it's position or negative (an int is fine: 0 is FALSE, non-zero is TRUE in C). So I'd do this:

C

#define TRUE 1
#define FALSE 0
#define POSITIVE TRUE
#define NEGATIVE FALSE
...
int NumberType = POSITIVE;
...
if (...)
   {
   NumberType = NEGATVE;
   }
...
printf("The number divided by 2 is %d and it's a %s number", Number, NumberType ? "POSITIVE" : "NEGATIVE");

Now your code is both more readable and easier to work with.