C Aptitude Questions and answers with explanation

C Aptitude 24
C program is one of most popular programming language which is used for core level of coding across the board. C program is used for operating systems, embedded systems, system engineering, word processors,hard ware drivers, etc.

In this site, we have discussed various type of C programs till date and from now on, we will move further by looking at the C aptitude questions.

The C aptitude questions and answers for those questions along with explanation for the interview related queries.

We hope that this questions and answers series on C program will help students and freshers who are looking for a job, and also programmers who are looking to update their aptitude on C program.
Some of the illustrated examples will be from the various companies, and IT industry experts.
Read more about how to prepare and write the C Aptitude Exams?
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

 

Predict the output or error(s) for the following:

C aptitude 24.1

main()

{

char str[4]="test";

printf("%s",str);


}

Answer: test#$634278621@!

Explanation: The character array has the memory just enough to hold the string “test” and doesn’t have enough space to store the terminating null character. So it prints the test correctly and continues to print garbage values till it accidentally comes across a NULL character.

C aptitude 24.2

 
main()

{

char * str = "hello";

char * ptr = str;

char least = 127;

while (*ptr++)

least = (*ptr <least ) ?*ptr :least;

printf("%d",least);

}

Answer: 0

Explanation: After ‘ptr’ reaches the end of the string the value pointed by ‘str’ is ‘’. So the value of ‘str’ is less than that of ‘least’. So the value of ‘least’ finally is 0.

C aptitude 24.3

     main()

{

int i = 257;

int *iPtr = &i;

printf("%d %d", *((char*)iPtr), *((char*)iPtr+1) );

}

Answer: 11

Explanation: The integer value 257 is stored in the memory as, 00000001 00000001, so the individual bytes are taken by casting it to char * and get printed.

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C Program to change the text colors.

Write a C Program to change the text colors.
In this program, we give the example of changing the text colors, background colors using conio.h library.
Syntax: void textcolor(int_color);
Here color is the integer variable, you can specify a color name also, but it should be a proper color name in capital letters.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

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* contact info@c-program-example.com
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* and browse!
*
* Happy Coding
***********************************************************/

#include<stdio.h>
#include<conio.h>
int main()
{
clrscr();
textcolor(BLUE); // Change font colour to blue
textbackground(WHITE); //change the background colour to white
cprintf("Color is Blue with white backgroundnn");
clrscr();
textcolor(RED+BLINK);//this one is blinking the text
cprintf("Color is RED with blinkingnn");
return 0;
}
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C Aptitude Questions and answers with explanation

C Aptitude 23
C program is one of most popular programming language which is used for core level of coding across the board. C program is used for operating systems, embedded systems, system engineering, word processors,hard ware drivers, etc.

In this site, we have discussed various type of C programs till date and from now on, we will move further by looking at the C aptitude questions.

The C aptitude questions and answers for those questions along with explanation for the interview related queries.

We hope that this questions and answers series on C program will help students and freshers who are looking for a job, and also programmers who are looking to update their aptitude on C program.
Some of the illustrated examples will be from the various companies, and IT industry experts.
Read more about how to prepare and write the C Aptitude Exams?
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

 

Predict the output or error(s) for the following:

C aptitude 23.1

void main(){
int res;
res= 56>76 ? return 0:return 1;
printf("%d",res);
}

Answer: Compilation error.

Explanation: We cannot use return keyword in conditional operator.

C aptitude 23.2
Note: here input for command line argument is, example 5 4 7 8

 
/* example.c */
#include

int main(int argc, char *argv[])
{
int j;
j = argv[1] + argv[2] + argv[3] + argv[4];
printf("%d", j);
return 0;
}

Answer: Error

Explanation: Command line arguments are string types, we can’t add or do the arithmetic operations on string types in C, we have to convert the argv[] to the integer types using atoi function.

C aptitude 23.3

     int main()
{
int num1 = 123;
float num2 = 123.0;
if(num1 == num2)
printf("num1 and num2 are equal");
else
printf("num1 and num2 are not equal");
return 0;
}

Answer: num1 and num2 are equal

Explanation: This is the tricky question, in if statement we are comparing 123=123.0, condition satisfied, so the result is num1 and num2 are equal.

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C program to sort a string

C Strings:
Write a C program to sort a string.
In this program we sort the string using bubble sort technique.
Bubble Sort is the simplest and easiest sorting technique. In this technique, the two successive items A[i] and A[i+1] are exchanged whenever A[i]>=A[i+1]. The larger values sink to the bottom of the array and hence it is called sinking sort. The end of each pass smaller values gradually “bubble” their way upward to the top(like air bubbles moving to surface of water) and hence called bubble sort.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

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* programs for commercial purposes,
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* and browse!
* 
*                      Happy Coding
***********************************************************/

#include<stdio.h>
#include<string.h>
int main(){
    int i,j,n;
    char str[50],temp[50];
    printf("Enter a String:nn");
    scanf("%s",str);
    n=strlen(str);
    for(i=0;i<=n;i++)
    for(j=i+1;j<=n;j++){
        if(strcmp(str[i],str[j])>0){
            strcpy(temp,str[i]);
            strcpy(str[i],str[j]);
            strcpy(str[j],temp);
        }
    }
    printf("The sorted string is:%sn",str);
    return 0;
}
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C Aptitude Questions and answers with explanation

C Aptitude 22
C program is one of most popular programming language which is used for core level of coding across the board. C program is used for operating systems, embedded systems, system engineering, word processors,hard ware drivers, etc.

In this site, we have discussed various type of C programs till date and from now on, we will move further by looking at the C aptitude questions.

In the coming days, we will post C aptitude questions, answers and explanation for interview preparations.

The C aptitude questions and answers for those questions along with explanation for the interview related queries.

We hope that this questions and answers series on C program will help students and freshers who are looking for a job, and also programmers who are looking to update their aptitude on C program.
Some of the illustrated examples will be from the various companies, and IT industry experts.
Read more about how to prepare and write the C Aptitude Exams?
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

 

Predict the output or error(s) for the following:

C aptitude 22.1

int main()
{
int *ptr;
*ptr=100;
return 0;
}

Answer: No error.

Explanation: At the time of compilation ,their is a no error, but at the run time you may caught up with the error “null pointer assignment”, because variable *ptr is not initialized during the declaration..

C aptitude 22.2

 
int main()
{
int example[]={2, 3, 4, 1, 6};
printf("%u, %u, %un", example, &example[0], &example);
return 0;
}

Answer: 1200 1200 1200

Explanation: In the printf statement example, &example are returning the base address of the array, i.e 1200, and &example[0] pointing to the address of the first element of array example, i.e 1200, so answer is 1200 1200 1200.

C aptitude 22.3

     int main()
{
char str1[20] = "Hello", str2[20] = " World";
printf("%sn", strcpy(str2, strcat(str1, str2)));
return 0;
}

Answer: Hello World

Explanation: In the printf statement strcat function concatenates or appends the string str2 to string str1, so str1 contains Hello World, then strcpy function copies the value of string str1 to string str2, so output is Hello World.

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Write a C program to reverse a string using pointers.

C Strings:
Write a C program to reverse a string using pointers.
In this program, we reverse the given string by using the pointers. Here we use the two pointers to reverse the string, strptr holds the address of given string and in loop revptr holds the address of the reversed string.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

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* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact info@c-program-example.com
* To find more C programs, do visit www.c-program-example.com
* and browse!
*
* Happy Coding
***********************************************************/

#include<stdio.h>
int main(){
int i=-1;
char str[100];
char rev[100];
char *strptr = str;
char *revptr = rev;
printf("Enter the string:n");
scanf("%s",str);
while(*strptr)
{
strptr++;
i++;
}
while(i >=0) {
strptr--;
*strptr = *revptr;
revptr++;
--i;
}
printf("nn Reversed string is:%s",rev);
return 0;
}



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C Aptitude Questions and answers with explanation

C Aptitude 19
C program is one of most popular programming language which is used for core level of coding across the board. C program is used for operating systems, embedded systems, system engineering, word processors,hard ware drivers, etc.

In this site, we have discussed various type of C programs till date and from now on, we will move further by looking at the C aptitude questions.

In the coming days, we will post C aptitude questions, answers and explanation for interview preparations.

The C aptitude questions and answers for those questions along with explanation for the interview related queries.

We hope that this questions and answers series on C program will help students and freshers who are looking for a job, and also programmers who are looking to update their aptitude on C program.
Some of the illustrated examples will be from the various companies, and IT industry experts.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

Predict the output or error(s) for the following:

C aptitude 19.1

  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 white-space) 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”.

C aptitude 19.2

  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.

C aptitude 19.3

     #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.

C aptitude 19.4

      int i=10;
main()
{
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: a'{‘ 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.

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C Aptitude Questions and answers with explanation

C Aptitude 18
C program is one of most popular programming language which is used for core level of coding across the board. C program is used for operating systems, embedded systems, system engineering, word processors,hard ware drivers, etc.

In this site, we have discussed various type of C programs till date and from now on, we will move further by looking at the C aptitude questions.

In the coming days, we will post C aptitude questions, answers and explanation for interview preparations.

The C aptitude questions and answers for those questions along with explanation for the interview related queries.

We hope that this questions and answers series on C program will help students and freshers who are looking for a job, and also programmers who are looking to update their aptitude on C program.
Some of the illustrated examples will be from the various companies, and IT industry experts.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

Predict the output or error(s) for the following:

C aptitude 18.1

  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 ‘’ termination character). The third sizeof is similar to the second one.

C aptitude 18.2

  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.

C aptitude 18.3

    #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”);
 }
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.

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C Aptitude Questions and answers with explanation

C Aptitude 17
C program is one of most popular programming language which is used for core level of coding across the board. C program is used for operating systems, embedded systems, system engineering, word processors,hard ware drivers, etc.

In this site, we have discussed various type of C programs till date and from now on, we will move further by looking at the C aptitude questions.

In the coming days, we will post C aptitude questions, answers and explanation for interview preparations.

The C aptitude questions and answers for those questions along with explanation for the interview related queries.

We hope that this questions and answers series on C program will help students and freshers who are looking for a job, and also programmers who are looking to update their aptitude on C program.
Some of the illustrated examples will be from the various companies, and IT industry experts.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

Predict the output or error(s) for the following:

C aptitude 17.1

  int i,j;
for(i=0;i<=10;i++)
{
j+=5;
assert(i<5);
}


Answer: Runtime error: Abnormal program termination. assert failed (i<5), ,

Explanation: sserts 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.

C aptitude 17.2

  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).

C aptitude 17.3

    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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C Aptitude Questions and answers with explanation

C Aptitude 15
C program is one of most popular programming language which is used for core level of coding across the board. C program is used for operating systems, embedded systems, system engineering, word processors,hard ware drivers, etc.

In this site, we have discussed various type of C programs till date and from now on, we will move further by looking at the C aptitude questions.

In the coming days, we will post C aptitude questions, answers and explanation for interview preparations.

The C aptitude questions and answers for those questions along with explanation for the interview related queries.

We hope that this questions and answers series on C program will help students and freshers who are looking for a job, and also programmers who are looking to update their aptitude on C program.
Some of the illustrated examples will be from the various companies, and IT industry experts.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

Predict the output or error(s) for the following:

C aptitude 15.1

  main()
{
extern out;
printf("%d", out);
}
int out=100;


Answer: 100

Explanation: This is the correct way of writing the previous program 14.3

C aptitude 15.2

 main()
{
show();
}
void show()
{
printf("I'm the greatest");
}

Answer: Compier error: Type mismatch in redeclaration of show.

Explanation:When the compiler sees the function show it doesn’t know anything about it. So the default return type (ie, int) is assumed. But when compiler sees the actual definition of show mismatch occurs since it is declared as void. Hence the error.
The solutions are as follows:
1. declare void show() in main() .
2. define show() before main().
3. declare extern void show() before the use of show().

C aptitude 15.3

    main( )
{
int a[ ] = {10,20,30,40,50},j,*p;
for(j=0; j<5; j++)
{
printf(“%d” ,*a);
a++;
}
p = a;
for(j=0; j<5; j++)
{
printf(“%d ” ,*p);
p++;
}
}

Answer:Compiler error: lvalue required..

Explanation: Error is in line with statement a++. The operand must be an lvalue and may be of any of scalar type for the any operator, array name only when subscripted is an lvalue. Simply array name is a non-modifiable lvalue.

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