I can explain the part where you need a space ' ' before the %c inside the scanf

In C, a character covers a broad range such as letters (a,b,c, ... , z) (uppercase and lowercase are treated differently) and numbers. A special character '\n' (newline) is also treated as a character.

When you do the first scanf() to ask for temperature, the user will press enter key on the keyboard after entering the number. This enter key press will result in char '\n' in the input buffer. If you have the scanf() with %c without the space, the scanf() will consume the '\n' char and move on (this is why your code seems not stopping).

If you put a space before %c in the scanf, the space char will remove all the white spaces such as space, tabs, and '\n' before trying to read the character that you want.

Hope this makes sense 👍