Basic Calculator Using C Language

 #include <stdio.h>

//function to add two numbers 

 int Add(int a,int b){

   return a+b;

 }

//function to substract two numbers

 int substract(int a,int b){

   return a-b;

 }

//function to multiply two numbers

 int multiply(int a,int b){

   return a*b;

 }

//function to divide two numbers

 int divide(int a,int b){

   return a/b;

 }

   int main(void) 

{

  int a,b,c;

  start:

  printf("\n_____calculator_____\n");

  printf("press 1 for addition\n");

  printf("press 2 for substraction\n");

  printf("press 3 for multiplication\n");

  printf("press 4 for division\n");

  printf("press 5 to quit\n");

  scanf ("\n%d", &c);

  if (c==1) {

    printf ("ADDITION\n");

  printf("enter any two number\n") ;

  scanf("%d", &a);

  scanf("%d",&b);

  printf("Addition = %d",Add(a,b));

    goto start;

  }

  else if(c==2){

    printf("\nSUBSTRACTION\n");

    printf("enter any two number\n") ;

  scanf("%d", &a);

  scanf("%d",&b);

  printf("Substraction = %d",substract(a,b));

goto start;

  }

  else if(c==3){

    printf ("\nMULTIPLICATION\n");

    printf("enter any two number\n") ;

    scanf("%d", &a);

    scanf("%d",&b);

    printf("Multiplication = %d",multiply(a,b));

    goto start;

  }

  else if(c==4){

    printf("\nDIVISION\n");

    printf("enter any two number\n") ;

    scanf("%d", &a);

    scanf("%d",&b);

    printf("Division = %d",divide(a,b));

  goto start;

  }

    else if (c==5){

      printf("quitting the program");

      goto end;

    }

  else{

    printf ("\ninvalid input");

  }

  end:

  return 0;

}

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