How to debug a C program producing unexpected output? - c

Question

I am new to programming C and I don't know why my program is not printing the desired output.
#include <stdio.h>
void main(void)
{
char res,res1;
float money=10;
printf("***Wealcome to Peace of Mind***");
printf("\nHello we have the menu please check::");
printf("\n***Menú***");
printf("\n");
printf("\n<<<Bebidas>>>");
printf("\n 1 - Coca-Cola = 1,5 2 - IceTea = 1,4");
printf("\n 3 - Super Bock = 1,70 4 - Sumol = 1,6");
printf("\n");
scanf("%d",&res);
switch(res)
{
case 1 || 'Coca-Cola':money - CocaCola;break;
}
printf("%.1f",money);
//Is that result i want:
printf("\n%.1f",10-1.5);
}
Output of my program:

Answer 1

The syntax of your case statement is not correct. Also the code is using scanf() to read an integer, but storing the integer-sized value in a char.
I tidied up the code:
#include <stdio.h>
int main(void)
{
int res;
float cost = 0;
float money = 10;
printf("***Wealcome to Peace of Mind***\n");
printf("Hello we have the menu please check::\n");
printf("***Menú***\n");
printf("\n");
printf("<<<Bebidas>>>\n");
printf(" 1 - Coca-Cola = 1,5 2 - IceTea = 1,4\n");
printf(" 3 - Super Bock = 1,70 4 - Sumol = 1,6\n");
printf("\n");
scanf("%d", &res);
switch(res)
{
case 1:
cost = 1.5;
break;
case 2:
cost = 1.4;
break;
// TODO: case 3 & 4
default:
printf("Invalid Entry\n");
cost = 0;
}
printf("money = %.1f\n", money - cost);
return 0;
}
Some further notes:
As commentators pointed out, put \n at the end of the string
When you compile, turn on warnings, and try to fix all of them.
In case blocks, it's good practice to have a default to catch errors
It would be worthwhile to store the drink prices as #define constants (or as an array of values, or some common area so the value is only set once in the program, and everything else just references that.)
#define COLA_COST 1.5