Process of = and == in if statement.

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in the given c programs what's the process takes place at assignment and equality operators?

What I have tried:

#include <stdio.h>
void main()
{
int x = 0;
if (x = 0)
printf("Its zero\n");
else
printf("Its not zero\n");
}
OUTPUT:Its not zero

#include <stdio.h>
void main()
{
int x = 0;
if (x == 0)
printf("Its zero\n");
else
printf("Its not zero\n");
}
OUTPUT:Its zero

Posted 24-Dec-17 0:52am

Venkatesh Pyla

Updated 24-Dec-17 2:37am

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2 solutions

Solution 2

Read and learn: C++ Built-in Operators, Precedence and Associativity[^]

Posted 24-Dec-17 2:37am

Richard MacCutchan

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Thomas Daniels · Accepted Answer · 2017-12-24T00:58:00

x = 0 sets the value of x to 0, whereas x == 0 is 'true' if x equals 0.

Let's take a look at your if statement in the first code block:

C

if (x = 0)

x = 0 sets the value of x to zero, but this expression has the new value of x (thus zero) as return value. So this if statement is equivalent to if (0) (with the additional effect that the value of x gets set to zero). 0 maps to false (all other integers map to true), so the else block gets executed.

In your second if block:

C

if (x == 0)

x == 0 is true, so the if block gets executed.