C language beginner's basic tutorial judgment
- 2020-05-30 20:50:38
- OfStack
(1)
Write a program first:
#include <stdio.h>
int main()
{
if(1)
{
printf("The condition is true!\n");
}
return 0;
}
Operation results:
The condition is true!
Then I changed the 1 to 2,5,100, -10, and found that the result was exactly the same.
If I change it to if(0), I will find that there is no result, indicating that the printf() statement has not been executed.
The C language takes as true any non-zero or non-null value in the judgment statement. So if(1), if(2), if(5), if(100), if(-10) have the same effect.
(2)
Write another program:
#include <stdio.h>
int main()
{
int a = 100;
if(a > 0)
{
printf("The condition value is %d\n", (a > 0));
}
return 0;
}
Operation results:
The condition value is 1
Analysis:
a = 100, a
>
0 is true, so if(a)
>
0) is the same thing as if of 1.
In C, the judgment statement has a value of either 1 or 0. For example, a in this program
>
The value of 0 is 1.
(3)
Finally, write a program:
#include <stdio.h>
int main()
{
char c1 = '\0';
if(c1)
{
printf("The condition is true!\n");
}
else
{
printf("The condition is false!\n");
}
char c2 = ' ';
if(c2)
{
printf("The condition is true!\n");
}
else
{
printf("The condition is false!\n");
}
char c3 = 'A';
if(c3)
{
printf("The condition is true!\n");
}
else
{
printf("The condition is false!\n");
}
return 0;
}
Operation results:
The condition is false!
The condition is true!
The condition is true!
Note: C USES '\0' to represent empty characters. The space ' 'is also one character, as you can see from the if(c2) condition that it is true.