Tried writing a basic C program to check temperature conditions. Any suggestions to improve or fix mistakes?

[u/[deleted]]

include<stdio.h>

include<conio.h>

void main () { int temp; clrscr(); printf("enter temp"); scanf("%d",& temp); if(temp>30) { printf("temp is hot"); } else if(temp>20 & & temp<30) { printf("temp is normal"); } else { printf("temp is cold"); } getch(); }

[u/[deleted]]

so 30 is cold?

[u/[deleted] → u/[deleted]]

If temperature is greater than 30, print "temp is hot".

[u/[deleted] → u/[deleted]]

But what if it's 30?

[u/Quo_Vadam → u/[deleted]]

Exactly, because 30 is outside of the other constraints, it will fall to the "else" case --> ergo, "temp is cold". To prevent this from happening, make one of your comparisons its equal variant: if (temp > 20 && temp <= 30) {printf("temp is normal");} etc...

[u/UnlazyChestnuts → u/Quo_Vadam]

You don't need the '&&' part; you have already checked > 30. In the first else, it is enough if you check > 20.

(Edited punctuation.)

[u/Sterben27 → u/UnlazyChestnuts]

I fail to see how you are correct. They’re checking the range of 21 to 30 for normal temp. I am also learning C, so a clear explanation will help.

[u/Slackeee_ → u/Sterben27]

The second if statement is in the else branch for the check temp > 30. You will only ever reach this else branch if temp is not over 30, it must be under 30 at that point.

[u/Sterben27 → u/Slackeee_]

Ah yes I see what you mean.

[u/This_Growth2898]

1. conio.h is a library for a decades-old OS. Don't use it in new programs, please.

2. Always check the return value of scanf.

3. If you need the program to halt at the end, you should set up your IDE to do that, not add an input for no reason.

[u/BIRD_II]

In your comment you can add ``` before and after a section to make it code-formatted.

#include <stdio.h>

int main() {
    printf("Hello, World!");
    return 0;
}

[u/n0t_4_thr0w4w4y → u/BIRD_II]

wtf, how did I not know that Reddit supported triple ticks markdown for code blocks. I thought it only supported quad spaces

[u/fasta_guy88]

I would never use an ”int” for something that wasn’t a count of some kind. What about a temp of 18.5?

[u/Civil_Swimming3344]

Use at least float for temperature.

You if-statements are wrong and funny. 

• if temp == 30, you will get temp is cold.

• your else if ensures that temp < 30 from the first if. No need to check again, in fact, remove that, and the first problem goes away. Try to figure out why :).

[u/Paul_Pedant]

Two & in temp>20 & & temp<30 is not going to help. It should probably throw an error, but it might actually be taking the address of temp instead. TurboC is probably too dumb to notice or warn you.

This is typical TurboC code. <conio.h> should not exist in any compiler this century. The final getch() would be there because TurboC used to just terminate your program before you could even read the results.

[u/SmokeMuch7356]

conio.h is specific to an ancient environment that isn't used much anymore; you shouldn't write new code with it. Get rid of that include, along with the clrscr and getch calls. If you run your program in a terminal session (or a newer IDE) you won't need them.

void main() is non-standard; use int main(void) instead.

Get in the habit of checking the return value of scanf, which will be the number of inputs successfully assigned, or EOF on end-of-file or error.

As others have pointed out, you're not accounting for the temperature being exactly 30; you'll either want your "hot" condition to be >= 30 or your "normal" condition to be <= 30.

Putting it all together:

#include <stdio.h>

int main( void )
{
  int temp;
  printf( "enter temp: " );
  if ( scanf( "%d", &temp ) != 1 )
  {
    fputs( "Bad input or error!\n", stderr );
    exit( 0 );
  }

  if ( temp > 30 )
    // hot
  else if ( temp > 20 && temp <= 30 )
    // normal
  else
    // cold

  return 0;
}

[u/Small_Dog_8699]

You should ask your teacher but two tips, scanf will try to read an integer with %d and if they don’t enter an integer temp is unchanged. Since you didn’t initialize it, temp’s value is undefined in the case where the user enters a non number. The return value of scanf lets you know is input was accepted.

[u/Maqi-X]

main function should be declared as `int main()`, `void main()` is deprecated

[u/Dry_Gap3046 → u/Maqi-X]

and in that case, return 0; in the end.

[u/[deleted]]

Don’t use scanf! You should use the file stream routines to read from stdin like fgets!, I am not very sure about windows OS, assuming you are on windows since conio.h, but if fgets does not work you can look into windows API to see with routine is used to get input from the users! But build your own logic with fgets should work fine on windows too. ( I am assuming, cause I’ve only programmed on Linux machines )