## Can the index of an array be negative?

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We can access the elements of an array by going through their indexes. But no programming language allows us to use a negative index value such as -4. Python programming language supports negative indexing of arrays, something which is not available in arrays in most other programming languages.

## What will happen if array index is negative in C?

It is invalid. By the C standard, it explicitly has undefined behavior.

**Does Fortran have 0 index?**

C arrays always start at zero, but by default Fortran arrays start at 1. There are two usual ways of approaching indexing.

**Can you have a negative index?**

What are negative indices? Negative indices are powers (also called exponents) with a minus sign in front of them. E.g. We get negative indices by dividing two terms with the same base where the first term is raised to a power that is smaller than the power that the second term is raised to.

### Is negative indexing allowed in CPP?

That means that you can have a pointer to the middle element of an array, and use it with a positive or negative index, and it’s simple arithmetic. That is, negative indexes here will be out of bounds of the array, and will lead to undefined behavior.

### What does negative index mean in C?

So, a[-1] means the element in the address 1000 + -1 , which is element in the address 999 . In other words, the integer, that precedes even the first element of the array.

**What is index in Fortran?**

INDEX(a1,a2) returns an integer value indicating the starting position within the character string a1 of a substring identical to string a2 . If a2 occurs more than once in a1 , the starting position of the first occurrence is returned. If a2 does not occur in a1 , the value zero is returned.

**What is Fortran index ordering?**

‘A’ means to read the elements in Fortran-like index order if a is Fortran contiguous in memory, C-like order otherwise. ‘K’ means to read the elements in the order they occur in memory, except for reversing the data when strides are negative. By default, ‘C’ index order is used.

#### How do I indicate to Fortran that we are using an array?

To indicate to FORTRAN that we are using an array, we just specify its size when we declare it. This snippet of code allocates 100 memory locations to the array x.

#### Why is there a negative 0 in Fortran 95?

This facility is provided in Fortran 95 because some processors, following an IEEE standard, have one bit pattern for positive zero and another for negative zero. 5.4 Numeric inquiry functions The precision of real number arithmetic, and the maximum and minimum sizes of real numbers, depend on the processor.

**What is a one-dimensional array in Fortran?**

Arrays can be one- dimensional (like vectors), two-dimensional (like matrices) and Fortran allows you to create up to 7-dimensional arrays. Arrays are declared with the dimension attribute. For example, to declare a one-dimensional array named number, of real numbers containing 5 elements, you write,

**How many strings are in a pointer array in Fortran?**

is an array of 30 strings each of 20 characters. Fortran 95 features not in Fortran 90 Pointers (Chapter 13) may be initially disassociated by pointer assignment to NULL (). Initialization of derived-type data is allowed, as in TYPE (Link), PARAMETER :: empty = Node(0, NULL())