Part1 | Part2 | ; Part3 | ; Part4
52) main ( )
{
static char *s[ ] = {“black”, “white”, “yellow”, “violet”};
char **ptr[ ] = {s+3, s+2, s+1, s}, ***p;
p = ptr;
**++p;
printf(“%s”,*--*++p + 3);
}
Answer:
ck
Explanation:
In this problem we have an array of char pointers pointing to start
of 4 strings. Then we have ptr which is a pointer to a pointer of
type char and a variable p which is a pointer to a pointer to a
pointer of type char. p hold the initial value of ptr, i.e. p = s+3.
The next statement increment value in p by 1 , thus now value of p
= s+2. In the printf statement the expression is evaluated *++p
causes gets value s+1 then the pre decrement is executed and we
get s+1 – 1 = s . the indirection operator now gets the value from
the array of s and adds 3 to the starting address. The string is
printed starting from this position. Thus, the output is ‘ck’.
53) main()
{
int i, n;
char *x = “girl”;
n = strlen(x);
*x = x[n];
for(i=0; i
Explanation:
asserts are used during debugging to make sure that certain
conditions are satisfied. If assertion fails, the program will
terminate reporting the same. After debugging use,
#undef NDEBUG
and this will disable all the assertions from the source code.
Assertion
is a good debugging tool to make use of.
55) main()
{
int i=-1;
+i;
printf("i = %d, +i = %d \n",i,+i);
}
Answer:
i = -1, +i = -1
Explanation:
Unary + is the only dummy operator in C. Where-ever it comes
you can just ignore it just because it has no effect in the
expressions (hence the name dummy operator).
56) What are the files which are automatically opened when a C file is
executed?
Answer:
stdin, stdout, stderr (standard input,standard output,standard
error).
57) what will be the position of the file marker?
a: fseek(ptr,0,SEEK_SET);
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b: fseek(ptr,0,SEEK_CUR);
Answer :
a: The SEEK_SET sets the file position marker to the starting of the
file.
b: The SEEK_CUR sets the file position marker to the current
position
of the file.
58) main()
{
char name[10],s[12];
scanf(" \"%[^\"]\"",s);
}
How scanf will execute?
Answer:
First it checks for the leading white space and discards it.Then it
matches with a quotation mark and then it reads all character upto
another quotation mark.
59) What is the problem with the following code segment?
while ((fgets(receiving array,50,file_ptr)) != EOF)
;
Answer & Explanation:
fgets returns a pointer. So the correct end of file check is checking
for != NULL.
60) main()
{
main();
}
Answer:
Runtime error : Stack overflow.
Explanation:
main function calls itself again and again. Each time the function is
called its return address is stored in the call stack. Since there is
no condition to terminate the function call, the call stack overflows
at runtime. So it terminates the program and results in an error.
61) main()
{
char *cptr,c;
void *vptr,v;
c=10; v=0;
cptr=&c; vptr=&v;
printf("%c%v",c,v);
}
Answer:
Compiler error (at line number 4): size of v is Unknown.
Explanation:
You can create a variable of type void * but not of type void, since
void is an empty type. In the second line you are creating variable
vptr of type void * and v of type void hence an error.
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62) main()
{
char *str1="abcd";
char str2[]="abcd";
printf("%d %d %d",sizeof(str1),sizeof(str2),sizeof("abcd"));
}
Answer:
2 5 5
Explanation:
In first sizeof, str1 is a character pointer so it gives you the size of
the pointer variable. In second sizeof the name str2 indicates the
name of the array whose size is 5 (including the '\0' termination
character). The third sizeof is similar to the second one.
63) main()
{
char not;
not=!2;
printf("%d",not);
}
Answer:
0
Explanation:
! is a logical operator. In C the value 0 is considered to be the
boolean value FALSE, and any non-zero value is considered to be
the boolean value TRUE. Here 2 is a non-zero value so TRUE.
!TRUE is FALSE (0) so it prints 0.
64) #define FALSE -1
#define TRUE 1
#define NULL 0
main() {
if(NULL)
puts("NULL");
else if(FALSE)
puts("TRUE");
else
puts("FALSE");
}
Answer:
TRUE
Explanation:
The input program to the compiler after processing by the
preprocessor is,
main(){
if(0)
puts("NULL");
else if(-1)
puts("TRUE");
else
puts("FALSE");
}
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Preprocessor doesn't replace the values given inside the double
quotes. The check by if condition is boolean value false so it goes
to else. In second if -1 is boolean value true hence "TRUE" is
printed.
65) main()
{
int k=1;
printf("%d==1 is ""%s",k,k==1?"TRUE":"FALSE");
}
Answer:
1==1 is TRUE
Explanation:
When two strings are placed together (or separated by whitespace)
they are concatenated (this is called as "stringization"
operation). So the string is as if it is given as "%d==1 is %s". The
conditional operator( ?: ) evaluates to "TRUE".
66) main()
{
int y;
scanf("%d",&y); // input given is 2000
if( (y%4==0 && y%100 != 0) || y%100 == 0 )
printf("%d is a leap year");
else
printf("%d is not a leap year");
}
Answer:
2000 is a leap year
Explanation:
An ordinary program to check if leap year or not.
67) #define max 5
#define int arr1[max]
main()
{
typedef char arr2[max];
arr1 list={0,1,2,3,4};
arr2 name="name";
printf("%d %s",list[0],name);
}
Answer:
Compiler error (in the line arr1 list = {0,1,2,3,4})
Explanation:
arr2 is declared of type array of size 5 of characters. So it can be
used to declare the variable name of the type arr2. But it is not the
case of arr1. Hence an error.
Rule of Thumb:
#defines are used for textual replacement whereas typedefs are
used for declaring new types.
68) int i=10;
main()
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{
extern int i;
{
int i=20;
{
const volatile unsigned i=30;
printf("%d",i);
}
printf("%d",i);
}
printf("%d",i);
}
Answer:
30,20,10
Explanation:
'{' introduces new block and thus new scope. In the innermost
block i is declared as,
const volatile unsigned
which is a valid declaration. i is assumed of type int. So printf
prints 30. In the next block, i has value 20 and so printf prints 20.
In the outermost block, i is declared as extern, so no storage space
is allocated for it. After compilation is over the linker resolves it to
global variable i (since it is the only variable visible there). So it
prints i's value as 10.
69) main()
{
int *j;
{
int i=10;
j=&i;
}
printf("%d",*j);
}
Answer:
10
Explanation:
The variable i is a block level variable and the visibility is inside
that block only. But the lifetime of i is lifetime of the function so it
lives upto the exit of main function. Since the i is still allocated
space, *j prints the value stored in i since j points i.
70) main()
{
int i=-1;
-i;
printf("i = %d, -i = %d \n",i,-i);
}
Answer:
i = -1, -i = 1
Explanation:
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-i is executed and this execution doesn't affect the value of i. In
printf first you just print the value of i. After that the value of the
expression -i = -(-1) is printed.
71) #include
main()
{
const int i=4;
float j;
j = ++i;
printf("%d %f", i,++j);
}
Answer:
Compiler error
Explanation:
i is a constant. you cannot change the value of constant
72) #include
main()
{
int a[2][2][2] = { {10,2,3,4}, {5,6,7,8} };
int *p,*q;
p=&a[2][2][2];
*q=***a;
printf("%d..%d",*p,*q);
}
Answer:
garbagevalue..1
Explanation:
p=&a[2][2][2] you declare only two 2D arrays. but you are trying
to access the third 2D(which you are not declared) it will print
garbage values. *q=***a starting address of a is assigned integer
pointer. now q is pointing to starting address of a.if you print *q
meAnswer:it will print first element of 3D array.
73) #include
main()
{
register i=5;
char j[]= "hello";
printf("%s %d",j,i);
}
Answer:
hello 5
Explanation:
if you declare i as register compiler will treat it as ordinary integer
and it will take integer value. i value may be stored either in
register or in memory.
74) main()
{
int i=5,j=6,z;
printf("%d",i+++j);
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}
Answer:
11
Explanation:
the expression i+++j is treated as (i++ + j)
76) struct aaa{
struct aaa *prev;
int i;
struct aaa *next;
};
main()
{
struct aaa abc,def,ghi,jkl;
int x=100;
abc.i=0;abc.prev=&jkl;
abc.next=&def;
def.i=1;def.prev=&abc;def.next=&ghi;
ghi.i=2;ghi.prev=&def;
ghi.next=&jkl;
jkl.i=3;jkl.prev=&ghi;jkl.next=&abc;
x=abc.next->next->prev->next->i;
printf("%d",x);
}
Answer:
2
Explanation:
above all statements form a double circular linked list;
abc.next->next->prev->next->i
this one points to "ghi" node the value of at particular node is 2.
77) struct point
{
int x;
int y;
};
struct point origin,*pp;
main()
{
pp=&origin;
printf("origin is(%d%d)\n",(*pp).x,(*pp).y);
printf("origin is (%d%d)\n",pp->x,pp->y);
}
Answer:
origin is(0,0)
origin is(0,0)
Explanation:
pp is a pointer to structure. we can access the elements of the
structure either with arrow mark or with indirection operator.
Note:
Since structure point is globally declared x & y are initialized as
zeroes
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78) main()
{
int i=_l_abc(10);
printf("%d\n",--i);
}
int _l_abc(int i)
{
return(i++);
}
Answer:
9
Explanation:
return(i++) it will first return i and then increments. i.e. 10 will be
returned.
79) main()
{
char *p;
int *q;
long *r;
p=q=r=0;
p++;
q++;
r++;
printf("%p...%p...%p",p,q,r);
}
Answer:
0001...0002...0004
Explanation:
++ operator when applied to pointers increments address
according to their corresponding data-types.
80) main()
{
char c=' ',x,convert(z);
getc(c);
if((c>='a') && (c<='z')) x=convert(c); printf("%c",x); } convert(z) { return z-32; } Answer: Compiler error Explanation: declaration of convert and format of getc() are wrong. 81) main(int argc, char **argv) { printf("enter the character"); http://www.exforsys.com Page 26 6/26/2004 26 getchar(); sum(argv[1],argv[2]); } sum(num1,num2) int num1,num2; { return num1+num2; } Answer: Compiler error. Explanation: argv[1] & argv[2] are strings. They are passed to the function sum without converting it to integer values. 82) # include
int one_d[]={1,2,3};
main()
{
int *ptr;
ptr=one_d;
ptr+=3;
printf("%d",*ptr);
}
Answer:
garbage value
Explanation:
ptr pointer is pointing to out of the array range of one_d.
83) # include
aaa() {
printf("hi");
}
bbb(){
printf("hello");
}
ccc(){
printf("bye");
}
main()
{
int (*ptr[3])();
ptr[0]=aaa;
ptr[1]=bbb;
ptr[2]=ccc;
ptr[2]();
}
Answer:
bye
Explanation:
ptr is array of pointers to functions of return type int.ptr[0] is
assigned to address of the function aaa. Similarly ptr[1] and ptr[2]
for bbb and ccc respectively. ptr[2]() is in effect of writing ccc(),
since ptr[2] points to ccc.
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85) #include
main()
{
FILE *ptr;
char i;
ptr=fopen("zzz.c","r");
while((i=fgetch(ptr))!=EOF)
printf("%c",i);
}
Answer:
contents of zzz.c followed by an infinite loop
Explanation:
The condition is checked against EOF, it should be checked against
NULL.
86) main()
{
int i =0;j=0;
if(i && j++)
printf("%d..%d",i++,j);
printf("%d..%d,i,j);
}
Answer:
0..0
Explanation:
The value of i is 0. Since this information is enough to determine
the truth value of the boolean expression. So the statement
following the if statement is not executed. The values of i and j
remain unchanged and get printed.
87) main()
{
int i;
i = abc();
printf("%d",i);
}
abc()
{
_AX = 1000;
}
Answer:
1000
Explanation:
Normally the return value from the function is through the
information from the accumulator. Here _AH is the pseudo global
variable denoting the accumulator. Hence, the value of the
accumulator is set 1000 so the function returns value 1000.
88) int i;
main(){
int t;
for ( t=4;scanf("%d",&i)-t;printf("%d\n",i))
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printf("%d--",t--);
}
// If the inputs are 0,1,2,3 find the o/p
Answer:
4--0
3--1
2--2
Explanation:
Let us assume some x= scanf("%d",&i)-t the values during
execution
will be,
t i x
4 0 -4
3 1 -2
2 2 0
89) main(){
int a= 0;int b = 20;char x =1;char y =10;
if(a,b,x,y)
printf("hello");
}
Answer:
hello
Explanation:
The comma operator has associativity from left to right. Only the
rightmost value is returned and the other values are evaluated and
ignored. Thus the value of last variable y is returned to check in if.
Since it is a non zero value if becomes true so, "hello" will be
printed.
90) main(){
unsigned int i;
for(i=1;i>-2;i--)
printf("c aptitude");
}
Explanation:
i is an unsigned integer. It is compared with a signed value. Since
the both types doesn't match, signed is promoted to unsigned
value. The unsigned equivalent of -2 is a huge value so condition
becomes false and control comes out of the loop.
91) In the following pgm add a stmt in the function fun such that the address
of
'a' gets stored in 'j'.
main(){
int * j;
void fun(int **);
fun(&j);
}
void fun(int **k) {
int a =0;
/* add a stmt here*/
}
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Answer:
*k = &a
Explanation:
The argument of the function is a pointer to a pointer.
92) What are the following notations of defining functions known as?
i. int abc(int a,float b)
{
/* some code */
}
ii. int abc(a,b)
int a; float b;
{
/* some code*/
}
Answer:
i. ANSI C notation
ii. Kernighan & Ritche notation
93) main()
{
char *p;
p="%d\n";
p++;
p++;
printf(p-2,300);
}
Answer:
300
Explanation:
The pointer points to % since it is incremented twice and again
decremented by 2, it points to '%d\n' and 300 is printed.
94) main(){
char a[100];
a[0]='a';a[1]]='b';a[2]='c';a[4]='d';
abc(a);
}
abc(char a[]){
a++;
printf("%c",*a);
a++;
printf("%c",*a);
}
Explanation:
The base address is modified only in function and as a result a
points to 'b' then after incrementing to 'c' so bc will be printed.
95) func(a,b)
int a,b;
{
return( a= (a==b) );
}
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main()
{
int process(),func();
printf("The value of process is %d !\n ",process(func,3,6));
}
process(pf,val1,val2)
int (*pf) ();
int val1,val2;
{
return((*pf) (val1,val2));
}
Answer:
The value if process is 0 !
Explanation:
The function 'process' has 3 parameters - 1, a pointer to another
function 2 and 3, integers. When this function is invoked from
main, the following substitutions for formal parameters take place:
func for pf, 3 for val1 and 6 for val2. This function returns the
result of the operation performed by the function 'func'. The
function func has two integer parameters. The formal parameters
are substituted as 3 for a and 6 for b. since 3 is not equal to 6,
a==b returns 0. therefore the function returns 0 which in turn is
returned by the function 'process'.
96) void main()
{
static int i=5;
if(--i){
main();
printf("%d ",i);
}
}
Answer:
0 0 0 0
Explanation:
The variable "I" is declared as static, hence memory for I will be
allocated for only once, as it encounters the statement. The function
main() will be called recursively unless I becomes equal to 0, and since
main() is recursively called, so the value of static I ie., 0 will be printed
every time the control is returned.
97) void main()
{
int k=ret(sizeof(float));
printf("\n here value is %d",++k);
}
int ret(int ret)
{
ret += 2.5;
return(ret);
}
Answer:
Here value is 7
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Explanation:
The int ret(int ret), ie., the function name and the argument name
can be the same.
Firstly, the function ret() is called in which the sizeof(float) ie., 4 is
passed, after the first expression the value in ret will be 6, as ret is
integer hence the value stored in ret will have implicit type conversion
from float to int. The ret is returned in main() it is printed after and
preincrement.
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