Page 145 - DCAP201_FUNDAMENTALS_OF_DATA_STRUCTURES

Fundamentals of Data Structures

Notes printf(“ STACK FULL, cannot insert more elements”);
exit(0);
}
stack[top]=element; /*Inserting an element to the stack which is an
array*/
printf(“THE TOP OF STACK IS %d”, stack[top]);
}
In the above code we can notice that line starts the beginning of the push() function which
accepts one argument that is the element to be inserted. The first operation we perform is to
increment the variable top which is a variable that holds the index value of the array and
practically holds the value of the TOP of stack. Initially the value of top is initialized to –1 which
means that the stack is empty initially. Hence it is incremented first so that the value of top will
be zero and it will be the first index of the array.

Figure 9.8: TOP = -1(no elements)

Source: http://newtonapples.com/operations-on-stack-c-language/

The variable size holds the size of the stack, i.e. the value of it suggests the maximum elements
that can be accepted by the stack. Hence in line 4 the condition top == stack-1 suggests practically
if the stack is full or not. The stack full condition is even known as stack overflow.

Notes The top variable increments on every insertion of element and when the value of
top is equal to the value of size–1 (–1 since stack is an array and it starts with 0), it means
that the stack cannot accept more elements.

Hence in line 5 we print a message that the stack is full and we cannot insert more elements. Line
6 executes the exit() function because it is not logical to get further in the function since we
cannot insert any more elements.

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