C Program Snippet Samples-1

1. void main()
   {
    int  const * p=5;
    printf("%d",++(*p));
   }

   Answer:

   Compiler error: Cannot modify a constant value.

   Explanation:

   p is a pointer to a "constant integer". But we tried to change the value of the "constant integer".

2. main()
   {
    char s[ ]="man";
    int i;
    for(i=0;s[ i ];i++)
    printf("\n%c%c%c%c",s[ i ],*(s+i),*(i+s),i[s]);
   }

   Answer:
   

   mmmm
   aaaa
   nnnn

   Explanation:
   

   s[i], *(i+s), *(s+i), i[s] are all different ways of expressing the same idea. Generally array name is the base address for that array. Here s is the base address. i is the index number/displacement from the base address. So, indirecting it with * is same as s[i]. i[s] may be surprising. But in the case of C it is same as s[i].

3. main()
   {
    float me = 1.1;
    double you = 1.1;
    if(me==you)
   printf("I love U");
   else
     printf("I hate U");
   }

   Answer:
   

   I hate U

   Explanation:
   

   For floating point numbers (float, double, long double) the values cannot be predicted exactly. Depending on the number of bytes, the precession with of the value represented varies. Float takes 4 bytes and long double takes 10 bytes. So float stores 0.9 with less precision than long double.

   Rule of Thumb:
   

   Never compare or at-least be cautious when using floating point numbers with relational operators (== , >, <, <=, >=,!= ).

   4.main()
    {
    static int var = 5;
    printf("%d ",var--);
    if(var)
     main();
    }

   Answer:

   5 4 3 2 1

   Explanation:

   When static storage class is given, it is initialized once. The change in the value of a static variable is retained even between the function calls. Main is also treated like any other ordinary function, which can be called recursively.

   5.main()
   

   {
     int c[ ]={2.8,3.4,4,6.7,5};
     int j,*p=c,*q=c;
     for(j=0;j<5;j++) {
     printf(" %d ",*c);
        ++q;   }
     for(j=0;j<5;j++){
   printf(" %d ",*p);
   ++p;   }
   }
   

   Answer:

   2 2 2 2 2 2 3 4 6 5