Calculator in C - c

Question

I've been trying to make a calculator in C and I am having some trouble cause when I said I wanted to choose again the program ends, or sometimes it works.
I tried this:
#include <stdio.h>
int main(void)
{
int xx;
int Y, N;
int a, b, c, d;
int aa, bb, Sum, ee, ff, Multi;
float cc, dd, Sub, gg, hh, Divi;
printf("\n\nC a l c u l a t o r\n\n");
printf("C h o o s e :\n\n");
printf(" S u m ( 1 ) \t");
printf(" S u b t r a c t i o n ( 2 )\n\n");
printf(" M u l t i p l i c a t i o n ( 3 ) \t");
printf(" D i v i s i o n ( 4 )\n\n");
scanf("%d", &xx);
a = 1;
b = 2;
c = 3;
d = 4;
Y = 10;
N = 20;
if (a == xx)
{
printf("\n\nE n t e r F i r s t N u m b e r :\n");
scanf("%d", &aa);
printf("\n\nE n t e r S e c o n d N u m b e r :\n");
scanf("%d", &bb);
Sum = aa + bb;
printf("%d + %d = %d", aa, bb, Sum);
xx = xx - 1;
printf("\n\nC h o o s e a g a i n ?\n");
printf(" ( Y e s = = S a y 1 0 !)\n");
printf(" ( N o = = S a y 2 0 !)\n");
scanf("%d", &xx);
if (Y == xx)
{
printf("\n\nC h o o s e :\n\n");
printf(" S u m ( 1 ) \t");
printf(" S u b t r a c t i o n ( 2 )\n\n");
printf(" M u l t i p l i c a t i o n ( 3 ) \t");
printf(" D i v i s i o n ( 4 )\n\n");
scanf("%d", &xx);
}
if (N == xx)
{
printf("\n\n F I N\n\n");
}
}
if (b == xx)
{
printf("\n\nE n t e r F i r s t N u m b e r :\n");
scanf("%f", &cc);
printf("\n\nE n t e r S e c o n d N u m b e r :\n");
scanf("%f", &dd);
Sub = cc - dd;
printf("%f - %f = %f", cc, dd, Sub);
xx = xx - 2;
printf("\n\nC h o o s e a g a i n ?\n");
printf(" ( Y e s = = S a y 1 0 !)\n");
printf(" ( N o = = S a y 2 0 !)\n");
scanf("%d", &xx);
if (Y == xx)
{
printf("\n\nC h o o s e :\n\n");
printf(" S u m ( 1 ) \t");
printf(" S u b t r a c t i o n ( 2 )\n\n");
printf(" M u l t i p l i c a t i o n ( 3 ) \t");
printf(" D i v i s i o n ( 4 )\n\n");
scanf("%d", &xx);
}
if (N == xx)
{
printf("\n\n F I N\n\n");
}
}
if (c == xx)
{
printf("\n\nE n t e r F i r s t N u m b e r :\n");
scanf("%d", &ee);
printf("\n\nE n t e r S e c o n d N u m b e r :\n");
scanf("%d", &ff);
Multi = ee * ff;
printf("%d x %d = %d", ee, ff, Multi);
xx = xx - 3;
printf("\n\nC h o o s e a g a i n ?\n");
printf(" ( Y e s = = S a y 1 0 !)\n");
printf(" ( N o = = S a y 2 0 !)\n");
scanf("%d", &xx);
if (Y == xx)
{
printf("\n\nC h o o s e :\n\n");
printf(" S u m ( 1 ) \t");
printf(" S u b t r a c t i o n ( 2 )\n\n");
printf(" M u l t i p l i c a t i o n ( 3 ) \t");
printf(" D i v i s i o n ( 4 )\n\n");
scanf("%d", &xx);
}
if (N == xx)
{
printf("\n\n F I N\n\n");
}
}
if (d == xx)
{
printf("\n\nE n t e r F i r s t N u m b e r :\n");
scanf("%f", &gg);
printf("\n\nE n t e r S e c o n d N u m b e r :\n");
scanf("%f", &hh);
Divi = gg / hh;
printf("%f / %f = %f", gg, hh, Divi);
xx = xx - 4;
printf("\n\nC h o o s e a g a i n ?\n");
printf(" ( Y e s = = S a y 1 0 !)\n");
printf(" ( N o = = S a y 2 0 !)\n");
scanf("%d", &xx);
if (Y == xx)
{
printf("\n\nC h o o s e :\n\n");
printf(" S u m ( 1 ) \t");
printf(" S u b t r a c t i o n ( 2 )\n\n");
printf(" M u l t i p l i c a t i o n ( 3 ) \t");
printf(" D i v i s i o n ( 4 )\n\n");
scanf("%d", &xx);
}
if (N == xx)
{
printf("\n\n F I N\n\n");
}
}
}
I've tried a lot of times trying to fix the code but it simply doesn't.

Answer 1

You have a lot of variables and repetition of code for no reason. I realize that my answer behaves differently than original question but looking at the code I don't think you understand what you really want. Start with this:
#include <stdio.h>
enum {
ADD = 1,
SUBTRACT,
MULTIPLY,
DIVIDE,
YES = 10,
NO = 20,
};
int main(void) {
int choice;
double values[2];
for(;;) {
printf(
"\n\nC a l c u l a t o r\n\n"
"C h o o s e :\n\n"
" S u m ( 1 ) \t"
" S u b t r a c t i o n ( 2 )\n\n"
" M u l t i p l i c a t i o n ( 3 ) \t"
" D i v i s i o n ( 4 )\n\n"
);
if(scanf(" %d", &choice) != 1) {
printf("scanf failed\n");
return 1;
}
printf("\n\nE n t e r F i r s t N u m b e r :\n");
if(scanf("%lf", &values[0]) != 1) {
printf("scanf failed\n");
return 1;
}
printf("\n\nE n t e r S e c o n d N u m b e r :\n");
if(scanf("%lf", &values[1]) != 1) {
printf("scanf failed\n");
return 1;
}
if (choice == ADD) {
double result = values[0] + values[1];
printf("%g + %g = %g", values[0], values[1], result);
} else if(choice == SUBTRACT) {
double result = values[0] - values[1];
printf("%g - %g = %g", values[0], values[1], result);
} else if(choice == MULTIPLY) {
double result = values[0] * values[1];
printf("%g * %g = %g", values[0], values[1], result);
} else if(choice == DIVIDE) {
if(values[1] == 0) {
printf("Cannot divide by zero\n");
} else {
double result = values[0] / values[1];
printf("%g / %g = %g", values[0], values[1], result);
}
}
printf("\n\nC h o o s e a g a i n ?\n");
printf(" ( Y e s = = S a y 1 0 !)\n");
printf(" ( N o = = S a y 2 0 !)\n");
if(scanf("%d", &choice) != 1) {
printf("scanf failed\n");
return 1;
}
if(choice == NO)
break;
}
printf("\n\n F I N\n\n");
}
The space between letters makes the prompt unnecessarily hard to read.
Consider changing the values you accept to be '+', '-', '*', '/' for the operators and 'y' and 'n' for the repeat prompts. This would be much easier on for the user of your program.
Should something different happen if either the first or 2nd choice is wrong? For instance, you could loop the prompt till you get a valid choice.