Introducing long

Long is a type of data that allows a plenty of numbers, if you need to show too much numbers, here's your type. By the way, signed and unsigned not work for long. Unsigned int is the same memory space for long, so use it as you want.

#include <stdio.h>

main()
{
      long st, nd;
     
      printf("Enter the first number ");
      scanf("%d", &st);
      printf("Enter the second number ");
      scanf("%d", &nd);
      printf("The result is %d", st * nd);
      getchar();
      getchar();
      getchar();
}

Introducing unsigned and signed

Just looking the signed and unsigned instructions, to be simple, unsigned is for numbers that are positive ONLY, and the signed is for negative numbers. This instructions goes before the data type, example, unsigned int. Here's an example code.

#include <stdio.h>

main()
{
      int st;
      signed int nd;
      unsigned int rd;
     
      st = -1;
      nd = -2;
      rd = 3;
     
      printf("The first number is %d", st);
      getchar();
      printf("The second number is %d", nd);
      getchar();
      printf("The third number is %d", rd);
      getchar();
}

Using formulas and multiplicating with variables

 The program will ask you for the numbers and show the result, for my opinion, I'll put a clrscr(); under the first getchar();. I have to learn the pow instruction, I knew how to do this without the math.h header but I lost that code. Nevermind, enjoy the program.

#include <stdio.h>

main()
{
      int a, b, st_rslt, nd_rslt;
      printf("Enter the first number ");
      scanf("%d", &a);
      printf("Enter the second number ");
      getchar();
      scanf("%d", &b);
      st_rslt = (a+b)*(a-b);
      nd_rslt = (a * a) - (b * b);
      printf("The result of the (a+b)*(a-b) formula is %d", st_rslt);
      getchar();
      getchar();
      printf("The result of the a^2-b^2 formula is %d", nd_rslt);
      getchar();
}