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    <p><code>\n</code> in <code>scanf</code> was the problem </p> <pre><code>#include&lt;stdio.h&gt; int main() { int marks[3]; int i; for(i=0;i&lt;3;i++) { printf("Enter a no\n"); scanf("%d",(marks+i)); } printf("\nEntered values:\n"); for(i=0;i&lt;3;i++) { printf("%d\n",*(marks+i)); } return 0; } </code></pre> <p><strong>Reason:</strong> </p> <blockquote> <p>I expect only <code>3</code> values is stored in an array but it stores 4 values and in next 'for' loop as expected show 3 values. My Question is why in 1st 'for' loop it takes 4 values instead of 3?</p> </blockquote> <p><strong>First:</strong> No, it only stores <code>3</code> number but not <code>4</code> numbers in array <code>marks[]</code>. </p> <p><strong>Second:</strong> interesting to understand loop runs only for three times for <code>i = 0</code> to <code>i &lt; 3</code>. The for loop runs according to condition. More interesting code is stuck in <code>scanf()</code> as described below: </p> <p>Your confusion is why you have to enter four numbers, its not because you loop runs <code>4</code> times but its because <code>scanf()</code> function returns only when you enter a non-space char (and after some <kbd>enter</kbd> press you inputs a number symbol that is non-space char). </p> <p>To understand this behavior read manual: <a href="http://man7.org/linux/man-pages/man3/scanf.3.html" rel="nofollow"><code>int scanf(const char *format, ...);</code></a>: </p> <blockquote> <p>A sequence of white-space characters (space, tab, newline, etc.; see <code>isspace(3)</code>). This directive <strong>matches any amount of white space, including none, in the input</strong>. </p> </blockquote> <p>Because in first for loop's, in <code>scanf()</code> you have included <code>\n</code> in format string, so <code>scanf()</code> returns only if press a number <kbd>enter</kbd> (or a non-space <kbd>key</kbd>). </p> <pre><code> scanf("%d\n",(marks+i)); ^ | new line char </code></pre> <p>What happens? </p> <p>Suppose input to program is: </p> <pre><code>23 &lt;--- because of %d 23 stored in marks[0] as i = 0 &lt;enter&gt; &lt;--- scanf consumes \n, still in first loop 543 &lt;--- scanf returns, and leave 542 unread, then in next iteration 543 read by scanf in next iteration &lt;enter&gt; 193 &lt;enter&gt; &lt;--- scanf consumes \n, still in 3rd loop &lt;enter&gt; &lt;--- scanf consumes \n, still in 3rd loop 123 &lt;--- remain unread in input stream </code></pre>
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    1. USGrijesh Chauhan
    1. USSanyam Goel
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    1. COthanx DX but when i used \n after %d in scanf, it takes 2 values first time when value of i is 0 but when value of i becomes 1 and 2 it takes only 1, why this happens?
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      1. USranaarjun
    2. COplease go through this http://answers.yahoo.com/question/index?qid=20110801122000AA07FO8 hope this gives you the exact reason
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    3. CO@GrijeshChauhan sure it will be helpful for all :) Please do
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