Q1: what does realloc(ptr, 0) and malloc(0) return?

Q2: how do you count all the bits in a number proportional to the number of bits set.

Q3: write a function that removes all of the spaces in a string (in linear time) without allocating additional memory. Modify the input string and remove the spaces from it, without being excessively slow. (good segway: Looking at this how does it relate to issues between memcpy and memmove?)

Q4: a linked list is broken and one of the nodes has broken off and points to a location in the middle. you wish to find which node this occured on to help you debug the problem. write a function that can find this looping point that uses a static amount of memory. it does not have to be fast.

Q5: what is the purpose of the volatile keyword?

Q6: describe this in plain english: char *foo[10];

Q7: write strncpy function

Q8: create a stack that wraps around at 5 elements.

Q9: describe what happens when a user enters "ls" from the keyboard into an xterm and what the shell does. complete round trip description, including the kernel, os and shell.

Q10: implement a queue using only stack operations. LIFO to FIFO.
    (hint: you can use two stacks)

Q11: how do you (in pure C) determine the direction of stack growth?

Q12: what order are function arguments pushed into the stack (do not consider stack growth direction)

Q13: what is the difference between LDT and GDT?

Q14: how does a system call work?

Q15: what are the three possible ways of providing system calls on x86? (old and new ways)

Q16: how can I make say these three for loops for (a=0;a<6;a++) for (b=0;b<6;b++) for (c=0;c<6;c++) in one recursive function ?

Q17: implement a function that solves the subset sub problem. brute force is allowed. for a set S of N numbers does a subset equal P. original: given a set of integers, does the sum of some non-empty subset equal exactly zero?

    { -7, -3, -2, 5, 8}  and 0 is one example.


Q18: what does if(7 < x < 49) { printf("Hello\n"); } do ?

Q19: Why does this program not print anything?
    #include <stdio.h>

    int main()
    {
        int i=0;
        while(i != 20, i++)
            printf("hello\n");
        return 0;
    }

Q20: What is wrong with this program (seems to segfault) ?
    int main()
    {
        char *a = "Hello ";
        char *b = "World!\n";
        strcat(a, b);
        return 0;
    }


Q21: Round a number down to the next boundry. Where B=100 and x=383, results should be 300.

Q22: Round a number up to the next boundry. Where B=100 and x=383, results should be 400. Carefully note what happens when a number already on a boundry is given, it shouldn't be x=300 shouldn't be rounded up.

Q23: what is the meant by a "stable sort" ? Is qsort() required to be stable?