C Interview Questions–to be solved

These programs were asked in various colleges/universities across India. These Questions were in my email dated 1999. So please let me know if any copyright information, so that I will remove it. But these questions are very much helpful for budding Student (engineers and interviewees).

//  Carefully study the given program

#include <stdio.h>
#include <alloc.h>

void main(void);

typedef struct NType
{
    int i;
    char c;
    long x;
}NewType;

void main(void)
{
    NewType *c;
    c=(NewType*)malloc(sizeof(NewType));
    c->i=100;
    c->c='C';
    (*c).x=100l;

    printf("%d,%c,%4ld",c->i,c->c,c->x);
}

/* What is the output of this program ?
a)  It will produce a variable redefinition error
b)  It will print some junk
c)  It will print 100,C,100
d)  It will print 100,C,l100
*/

// Carefully go through the following program
#include <stdio.h>

void main(void);

const int k=100;

void main(void)
{
   int a[100];
   int sum=0;

   for(k=0;k<100;k++)
    *(a+k)=k;
    sum += a[--k];
   printf("%d",sum);
}

/*
What will be the out put of this program ?
a) It will print the sum of all the elements
b) It will print 99
c) It will produce a runtime error
d) None of the above
*/

// Read the following program carefully
#include <stdio.h>

void main(void);
int printf(const char*,...);

void main(void)
{
   int i = 100,j=10,k=20;
   int sum;
   float ave;
   char myformat[]="ave = %.2f";
   sum=i+j+k;
   ave=sum/3;

   printf(myformat,ave);
}

/*
What will the above program do ?
a) It will print 43.33
b) It will print 43.34
c) It will produce a compilation error
d) None of the above
*/

//   Consider the following program code
#include <stdio.h>
void main(void)
{
    int a[10];
    printf("%d",*(a/(a+9)));
}

/* What will the program do ?
a)  It will print some junk as array a is not initialised.
b)  It will result in a compilation error.
c)  It will produce a runtime error as array a is not initialised.
d)  None of the above. */

//   Carefully go through the following code
#include <stdio.h>
void main(void);

void main(void)
{
    struct s{
        int x;
        float y;
        }s1 = {25,45.00};

    union u{
        int x;
        float y;
        }u1;

        u1=(union u)s1;

        printf("%d and %f",u1.x,u1.y);
}

/* What will this program point ?

a)  25 and 45.00
b)  Produce a compilation error
c)  45 and 45.00
d)  Produce a runtime error  */

//  Consider the following C program.
#include <stdio.h>
void main(void)
{
    unsigned int c;
    unsigned x=0x0003;
    scanf("%u",&c);

    switch(c&x)
    {
        case 3 : printf("Hello! \t");
        case 2 : printf("Welcome \t");
        case 1 : printf("To All \t");
        default: printf("\n");
}
}

/* If the value input for the variable c is 10, what will be the output
of the program ?

a)  The program will generate a compile time error as there is no break
    statement for the various case choices.
b)  The program will print Hello!
c)  The program will print Welcome    To All
d)  None of the above  */

// 16)
#include <stdio.h>
// print the sum of series 1/5 + 1/4 + ...
static int i=5;

void main(void)
{
    int sum = 0;
    do
    {
        sum+=(1/i);
    }while (0 < i--);
}

/* What will this program output ?
a)  It will point the sum of the series 1/5 + 1/4 + ... + 1/1
b)  It will produce a compilation error
c)  It will produce a runtime error
d)  None of the above
*/

//

#include <stdio.h>

void main(void);

void main(void)
{
    int i = 100,j=20;

    i++=j;
    i*=j;

    printf("%d\t%d\n",i,j);
}

/*  What will this program output ?
a)  It will print 400    20
b)  It will produce a compilation error
c)  It will print 401    21
d)  It will print some garbage
*/

// 18) What will the following program do ?
#include <stdio.h>
int fn(void);
void print(int,int(*)());

int i = 10;

void main(void)
{
    int i = 20;
    print(i,fn);
}

void print(int i,int (*fn1)())
{
    printf("%d\n",(*fn1)());
}

int fn(void)
{
    return(i-=5);
}

/*
a) There will be a compilation error.
b) It will print 5
c) There will be a linkage error as there is no fn1() function definition
d) both (a) and (c).
*/

//    1)    Consider the following program
#include <stdio.h>
void main()
{
    int y,z;
    int x=y=z=10;
    int f=x;
    float ans=0.0;

    f=x*y;
    ans=x/3.0 + y/3;
    printf("%d,%.2f",f,ans);
}

/*    What will be the output of this program ?
    a)    It will print 1000,6.66;
    b)    It will give a type mismatch error;
    c)    It will generate a compile-time error;
    d)    None of the above;
*/

//    2)    Study the following code carefully
#include <stdio.h>
void main(void);
double dbl=20.4530,d=4.5710,dblvar3;

void main()
{
    double dbfn(void);
    dblvar3=dbfn();
    printf("%.2f\t%.2f\t%.2f\n",dbl,d,dblvar3);
}

double dbfn(void)
{
    double d,dblvar3;
    dbl=d=dblvar3=4.5;
    return(dbl+d+dblvar3);
}

/*    The output of the above program will be
    a)    4.50    4.57    29.52;
    b)    4.50    4.57    13.50;
    c)    4.57    4.57    29.52;
    d)    4.57    4.50    13.50; */

//    3)    Consdier the following program
#include <stdio.h>
int SumElement(int *,int);

void main(void)
{
    int x[10];
    int i=10;
    for(;i;)
    {
        i--;
        *(x+i)=i;
    }
    printf("%d",SumElement(x,10));
}

int SumElement(int array[],int size)
{
    int i=0;
    float sum=0;
    for(;i<size;i++)
        sum+=array[i];
    return sum;
}

/*    What will be the output of this program ?
    a) It will print 45;
    b) It will produce a type mismatch error as SumElement's return
        statement returns a float;
    c) It will produce a compilation error in statement for(;,i,;);
    d) Both (b) and (c); */

  // 4) Carefully study the following
#include <stdio.h>

void main(void)
{
    int oldvar=25, newvar=-25;
    int swap(int,int);
    swap(oldvar,newvar);
    printf("Numbers are %d \t %d",newvar,oldvar);
}

int swap(int oldval,int newval)
{
    int tempval= oldval;
        oldval = newval;
        newval = tempval;
}

/*     The output of this program will be
    a)  Numbers are 25  -25
    b)    Numbers are 25   25
    c)  Numbers are -25  25
    d)    Numbers are -25 -25  */

// 5) Consider the following program
#include <stdio.h>

void main(void);
int newval(int);

void main(void)
{
    int ia[]={12,24,45,0};
    int i,sum=0;

    for(i=0;ia[i];i++)
    {
        sum+=newval(ia[i]);
    }
    printf("Sum = %d",sum);
}

int newval(int x)
{
    static int div = 1;
    return (x/div++);
}

/*     The output of this program will be
    a)  Sum = 61;
    b)    Sum = 39;
    c)  Runtime error
    d)    Compilation error */

// 6)  Study the following program
#include <stdio.h>
void main(void);

void main(void)
{
    int var1=5,var2=5,var3=6,minmax;
    minmax = (var1 > var2) ? (var1 > var3) ? var1:var3:(var2 > var3) ? var2:var3;
    printf("%d\n",minmax);
}

/*  This program will
    a)  Produce a runtime error
    b)  Produce a compilation error
    c)  Print 5
    d)  Print 6 */

// 7) Consider the following program
#include <stdio.h>
void main(void);

void main(void)
{
    void pa(int *a,int n);
    int arr[5]={5,4,3,2,1};
    pa(arr,5);
}

void pa(int *a,int n)
{
    int i;
    for(i=0;i<n;i++)
        printf("%d\n",*(a++)+i);
}

/*  Which of the following is correct ?
    a)  The Program prints the alternate elements of array.
    b)  It will not compile as 'array' cannot be incremented.
    c)  It will print 6,5,4,3,2 on individual lines.
    d)  It will print 5 five times 6 */

// 8)  Consider the program in two files.
// The content of the file1.c is
#include <stdio.h>
void main(void);
void print(void);

void main(void)
{
    print();
}

void f1(void)
{
    printf("\n f1();");
}

// and the content of the file2.c is
#include <stdio.h>

void print(void)
{
    extern void f1(void);
    f1();
}
static void f1(void)
{
    printf("\n static f1();");
}

/*  Which will be the output of the program ?
    a)  It will print f1().
    b)  It will print the value returned by f1().
    c)  It will produce a compile-time error as f1() is defined twice.
    d)  None of the above */

// 9) Read the following code
#include <stdio.h>
void main(void);

static int i=50;
int print(int i);

void main(void)
{
    static int i=100;
    while (print(i))
    {
        printf("%d\n",i);
        i--;
    }
}
int print(int x)
{
    static int i = 2;
    return(i--);
}

/* What will be the output of this program ?
a)  It will print from 100 to 0 in steps of -1
b)  It will print 100 and 99 on two steps
c)  It will print 100,99 and 98 and stop
d)  None of the above
*/

-----------------

//  10)  Carefully study the given program

#include <stdio.h>
#include <alloc.h>

void main(void);

typedef struct NType
{
    int i;
    char c;
    long x;
}NewType;

void main(void)
{
    NewType *c;
    c=(NewType*)malloc(sizeof(NewType));
    c->i=100;
    c->c='C';
    (*c).x=100l;

    printf("%d,%c,%4ld",c->i,c->c,c->x);
}

/* What is the output of this program ?
a)  It will produce a variable redefinition error
b)  It will print some junk
c)  It will print 100,C,100
d)  It will print 100,C,l100
*/

//  11) Carefully go through the following program
#include <stdio.h>

void main(void);

const int k=100;

void main(void)
{
   int a[100];
   int sum=0;

   for(k=0;k<100;k++)
    *(a+k)=k;
    sum += a[--k];
   printf("%d",sum);
}

/*
What will be the out put of this program ?
a) It will print the sum of all the elements
b) It will print 99
c) It will produce a runtime error
d) None of the above
*/

// 12) Read the following program carefully
#include <stdio.h>

void main(void);
int printf(const char*,...);

void main(void)
{
   int i = 100,j=10,k=20;
   int sum;
   float ave;
   char myformat[]="ave = %.2f";
   sum=i+j+k;
   ave=sum/3;

   printf(myformat,ave);
}

/*
What will the above program do ?
a) It will print 43.33
b) It will print 43.34
c) It will produce a compilation error
d) None of the above
*/

// 13)  Consider the following program code
#include <stdio.h>
void main(void)
{
    int a[10];
    printf("%d",*(a/(a+9)));
}

/* What will the program do ?
a)  It will print some junk as array a is not initialised.
b)  It will result in a compilation error.
c)  It will produce a runtime error as array a is not initialised.
d)  None of the above. */

// 14)  Carefully go through the following code
#include <stdio.h>
void main(void);

void main(void)
{
    struct s{
        int x;
        float y;
        }s1 = {25,45.00};

    union u{
        int x;
        float y;
        }u1;

        u1=(union u)s1;

        printf("%d and %f",u1.x,u1.y);
}

/* What will this program point ?

a)  25 and 45.00
b)  Produce a compilation error
c)  45 and 45.00
d)  Produce a runtime error  */

// 15) Consider the following C program.
#include <stdio.h>
void main(void)
{
    unsigned int c;
    unsigned x=0x0003;
    scanf("%u",&c);

    switch(c&x)
    {
        case 3 : printf("Hello! \t");
        case 2 : printf("Welcome \t");
        case 1 : printf("To All \t");
        default: printf("\n");
}
}

/* If the value input for the variable c is 10, what will be the output
of the program ?

a)  The program will generate a compile time error as there is no break
    statement for the various case choices.
b)  The program will print Hello!
c)  The program will print Welcome    To All
d)  None of the above  */

// 16)
#include <stdio.h>
// print the sum of series 1/5 + 1/4 + ...
static int i=5;

void main(void)
{
    int sum = 0;
    do
    {
        sum+=(1/i);
    }while (0 < i--);
}

/* What will this program output ?
a)  It will point the sum of the series 1/5 + 1/4 + ... + 1/1
b)  It will produce a compilation error
c)  It will produce a runtime error
d)  None of the above
*/

// 17)
#include <stdio.h>

void main(void);

void main(void)
{
    int i = 100,j=20;

    i++=j;
    i*=j;

    printf("%d\t%d\n",i,j);
}

/*  What will this program output ?
a)  It will print 400    20
b)  It will produce a compilation error
c)  It will print 401    21
d)  It will print some garbage
*/

// 18) What will the following program do ?
#include <stdio.h>
int fn(void);
void print(int,int(*)());

int i = 10;

void main(void)
{
    int i = 20;
    print(i,fn);
}

void print(int i,int (*fn1)())
{
    printf("%d\n",(*fn1)());
}

int fn(void)
{
    return(i-=5);
}

/*
a) There will be a compilation error.
b) It will print 5
c) There will be a linkage error as there is no fn1() function definition
d) both (a) and (c).
*/

//    1)    Consider the following program
#include <stdio.h>
void main()
{
    int y,z;
    int x=y=z=10;
    int f=x;
    float ans=0.0;

    f=x*y;
    ans=x/3.0 + y/3;
    printf("%d,%.2f",f,ans);
}

/*    What will be the output of this program ?
    a)    It will print 1000,6.66;
    b)    It will give a type mismatch error;
    c)    It will generate a compile-time error;
    d)    None of the above;
*/

//    2)    Study the following code carefully
#include <stdio.h>
void main(void);
double dbl=20.4530,d=4.5710,dblvar3;

void main()
{
    double dbfn(void);
    dblvar3=dbfn();
    printf("%.2f\t%.2f\t%.2f\n",dbl,d,dblvar3);
}

double dbfn(void)
{
    double d,dblvar3;
    dbl=d=dblvar3=4.5;
    return(dbl+d+dblvar3);
}

/*    The output of the above program will be
    a)    4.50    4.57    29.52;
    b)    4.50    4.57    13.50;
    c)    4.57    4.57    29.52;
    d)    4.57    4.50    13.50; */

//    3)    Consdier the following program
#include <stdio.h>
int SumElement(int *,int);

void main(void)
{
    int x[10];
    int i=10;
    for(;i;)
    {
        i--;
        *(x+i)=i;
    }
    printf("%d",SumElement(x,10));
}

int SumElement(int array[],int size)
{
    int i=0;
    float sum=0;
    for(;i<size;i++)
        sum+=array[i];
    return sum;
}

/*    What will be the output of this program ?
    a) It will print 45;
    b) It will produce a type mismatch error as SumElement's return
        statement returns a float;
    c) It will produce a compilation error in statement for(;,i,;);
    d) Both (b) and (c); */

  // 4) Carefully study the following
#include <stdio.h>

void main(void)
{
    int oldvar=25, newvar=-25;
    int swap(int,int);
    swap(oldvar,newvar);
    printf("Numbers are %d \t %d",newvar,oldvar);
}

int swap(int oldval,int newval)
{
    int tempval= oldval;
        oldval = newval;
        newval = tempval;
}

/*     The output of this program will be
    a)  Numbers are 25  -25
    b)    Numbers are 25   25
    c)  Numbers are -25  25
    d)    Numbers are -25 -25  */

// 5) Consider the following program
#include <stdio.h>

void main(void);
int newval(int);

void main(void)
{
    int ia[]={12,24,45,0};
    int i,sum=0;

    for(i=0;ia[i];i++)
    {
        sum+=newval(ia[i]);
    }
    printf("Sum = %d",sum);
}

int newval(int x)
{
    static int div = 1;
    return (x/div++);
}

/*     The output of this program will be
    a)  Sum = 61;
    b)    Sum = 39;
    c)  Runtime error
    d)    Compilation error */

// 6)  Study the following program
#include <stdio.h>
void main(void);

void main(void)
{
    int var1=5,var2=5,var3=6,minmax;
    minmax = (var1 > var2) ? (var1 > var3) ? var1:var3:(var2 > var3) ? var2:var3;
    printf("%d\n",minmax);
}

/*  This program will
    a)  Produce a runtime error
    b)  Produce a compilation error
    c)  Print 5
    d)  Print 6 */

// 7) Consider the following program
#include <stdio.h>
void main(void);

void main(void)
{
    void pa(int *a,int n);
    int arr[5]={5,4,3,2,1};
    pa(arr,5);
}

void pa(int *a,int n)
{
    int i;
    for(i=0;i<n;i++)
        printf("%d\n",*(a++)+i);
}

/*  Which of the following is correct ?
    a)  The Program prints the alternate elements of array.
    b)  It will not compile as 'array' cannot be incremented.
    c)  It will print 6,5,4,3,2 on individual lines.
    d)  It will print 5 five times 6 */

// 8)  Consider the program in two files.
// The content of the file1.c is
#include <stdio.h>
void main(void);
void print(void);

void main(void)
{
    print();
}

void f1(void)
{
    printf("\n f1();");
}

// and the content of the file2.c is
#include <stdio.h>

void print(void)
{
    extern void f1(void);
    f1();
}
static void f1(void)
{
    printf("\n static f1();");
}

/*  Which will be the output of the program ?
    a)  It will print f1().
    b)  It will print the value returned by f1().
    c)  It will produce a compile-time error as f1() is defined twice.
    d)  None of the above */

// 9) Read the following code
#include <stdio.h>
void main(void);

static int i=50;
int print(int i);

void main(void)
{
    static int i=100;
    while (print(i))
    {
        printf("%d\n",i);
        i--;
    }
}
int print(int x)
{
    static int i = 2;
    return(i--);
}

/* What will be the output of this program ?
a)  It will print from 100 to 0 in steps of -1
b)  It will print 100 and 99 on two steps
c)  It will print 100,99 and 98 and stop
d)  None of the above
*/