Basic Conditional Checking for IF statements in C
Can someone please explain what really 开发者_运维技巧goes on in this code ? If I put the AND statement, the message wont show if values are less than 0 or greater than 10 ... I think I must use 1 0 logic to work this out right ? I just need someone to briefly explain it please.
#include<stdio.h>
main(){
puts("enter number");
scanf("%d",num);
if(num<0 || num >10)
puts("yay");
}
How is that IF statement different when AND is put :
#include<stdio.h>
main(){
puts("enter number");
scanf("%d",num);
if(num<0 && num >10)
puts("yay");
}
Thanks !!
This is based on Boolean logic:
true || true -> true
true || false -> true
false || true -> true
false || false -> false
true && true -> true
true && false -> false
false && true -> false
false && false -> false
Notice how those differ when one side is true and the other is false.
Anyway, in your test:
if(num<0 && num >10)
It's not possible for a number to both be < 0
and at the same time be > 10
. Because of this, you will either evaluate true && false
(for negative numbers), false && false
(for numbers between 0 and 10 inclusive) or false && true
(for numbers larger then 10). In all those cases, the boolean logic says the answer is false
.
Boolean logic.
If you use || (OR), the statement is true if ANY of the conditions are met. If you use && (AND), the statement is true ONLY if ALL of the conditions are met. SO in your second example, the statement will be true if the number is BOTH smaller than 0 AND larger than 10. Clearly there is no such number.
1) I believe you forgot some char in scanf string:
scanf("%d",&num);
2) first example will say "yay" if number is LESS THAN 0 or GREATER THAN 10
second example will never say "yay" b/c number must be LESS THAN 0 and GREATER THAN 10 simultaneously
精彩评论