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C Program to Read integers into an array and Reversing them using Pointers
/* C Program to Read integers into an array and Reversing them using Pointers
Write a C program using pointers to read in an array of integers and print its elements in reverse order.
We have declared one pointer variable and one array.
Address of first element of array is stored inside pointer variable.
Accept Size of an Array.
Now we have accepted element one by one using for loop and scanf statement .
Increment pointer variable so that it will then point to next element of array.
After accepting all elements store address of last element inside pointer variable.
Again using reverse for loop and printf statement print an array. */
#include<stdio.h>
#include<conio.h>
#define MAX 30
void main() {
int size, j, arr[MAX];
int *ptr;
clrscr();
ptr = &arr[0];
printf("\nEnter the size of array : ");
scanf("%d", &size);
printf("\nEnter %d integers into array: ", size);
for (j = 0; j < size; j++) {
scanf("%d", ptr);
ptr++;
}
ptr = &arr[size - 1];
printf("\nElements of array in reverse order are :");
for (j = size - 1; j >= 0; j--) {
printf("\nElement%d is %d : ", j, *ptr);
ptr--;
}
getch();
}
In C, the "main" function is treated the same as every function, it has a return type (and in some cases accepts inputs via parameters). The only difference is that the main function is "called" by the operating system when the user runs the program. Thus the main function is always the first code executed when a program starts. main() function is a user defined, body of the function is defined by the programmer or we can say main() is programmer/user implemented function, whose prototype is predefined in the compiler. Hence we can say that main() in c programming is user defined as well as predefined because it's prototype is predefined. main() is a system (compiler) declared function whose defined by the user, which is invoked automatically by the operating system when program is being executed.
Function clrscr() clears the screen and moves the cursor to the upper left-hand corner of the screen. If you are using the GCC compiler, use system function to execute the clear/cls command. clrscr() function is also a non-standard function defined in "conio.h" header. This function is used to clear the console screen. It is often used at the beginning of the program (mostly after variable declaration but not necessarily) so that the console is clear for our output.
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Pointers in C are easy and fun to learn. Some C programming tasks are performed more easily with pointers, and other tasks, such as dynamic memory allocation, cannot be performed without using pointers. So it becomes necessary to learn pointers to become a perfect C programmer. Let's start learning them in simple and easy steps. As you know, every variable is a memory location and every memory location has its address defined which can be accessed using ampersand (&) operator, which denotes an address in memory. Consider the following example, which prints the address of the variables defined. A pointer is a variable whose value is the address of another variable, i.e., direct address of the memory location. Like any variable or constant, you must declare a pointer before using it to store any variable address. The general form of a pointer variable declaration is:
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