while loop unexpected (character to int conversion)

Question

#include<stdio.h>
main()
char i=13;
while(i)
{
i++;
}
printf("%d",i);
}

the out put turns out to be zero . how come does it happen

#include<stdio.h>
main()
char i=48;
if(i)
{
printf("%d",i);
}
   }

this program run sucessfully and prints 48. isn't i considered a character o for which it is supposed to fail .How is i stored in the memory as a character or a number

Answer 1

You're missing a bracket after 'main()'. Your first code actually keeps counting up from 13, until it hits 127 (if, on your system, chars are represented as signed integers) because this is the largest positive integer for a char on such a system; then flips to -128 and keeps counting up to 0. At 0, you exit your loop, and print the result. To visualize what happens, copy this and try it out:

#include <stdio.h>

int main()
{
    char i=13;
    while(i){
        i++;
        printf("%d ", i);
    }

    printf("\n%d",i);
}

Output:

14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 -128 -127 -126 -125 -124 -123 -122 -121 -120 -119 -118 -117 -116 -115 -114 -113 -112 -111 -110 -109 -108 -107 -106 -105 -104 -103 -102 -101 -100 -99 -98 -97 -96 -95 -94 -93 -92 -91 -90 -89 -88 -87 -86 -85 -84 -83 -82 -81 -80 -79 -78 -77 -76 -75 -74 -73 -72 -71 -70 -69 -68 -67 -66 -65 -64 -63 -62 -61 -60 -59 -58 -57 -56 -55 -54 -53 -52 -51 -50 -49 -48 -47 -46 -45 -44 -43 -42 -41 -40 -39 -38 -37 -36 -35 -34 -33 -32 -31 -30 -29 -28 -27 -26 -25 -24 -23 -22 -21 -20 -19 -18 -17 -16 -15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0

The positive to negative change has to do with the IEEE representation of integers on computers. You can find many related questions on SO if you google for them.

Answer 2

An if statement compares the numeric value, not the ASCII character that it happens to represent. Only the numeric value 0 will result in the if failing to execute in your second example.